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On February 1, 1958, the Russians launched the first-ever artificial satellite to space. 

It was called Sputnik I. Sputnik I orbited the Earth from a height of 577 km at a speed of 8 km/s. It travelled a total distance of 70 million km, completing 1,440 orbits around our planet.

Three years later, Russian Astronaut, Yuri Gagarin became the first man to go to space. In the earliest space capsule ever made by humans, Gagarin orbited the Earth, just like Sputnik I, in 89 minutes. In July 1969, American Astronaut Neil Armstrong became the first human to step on the Moon.

On December 25, 2021, NASA launched the James Webb Space Telescope to an orbit that is 1.5 million km away from the Earth. The telescope, which orbits the Sun like the Earth and all other objects in the Solar System, sent us unbelievably marvellous images of long-dead stars by detecting infrared waves in. That happened in July 2022.

Such great technological advancements that allowed more space exploration were only made possible by the efforts of great scientists, astronomers, and mathematicians. Those are the people who have dedicated their lives to studying our planet, the Solar System, and outer space.

One, therefore, can never mention space without paying tribute to the man who was named the Father of Modern Astronomy: Galileo Galilei. And this is what today’s lesson is about.

So let’s hop into it.

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(1) Who was Galileo Galilei?

Mostly known by his first name, Galileo was an Italian astronomer. Many people consider him a polymath because he had a wide knowledge in a variety of fields including mathematics, astronomy, physics, and philosophy. He was born in Pisa, Italy in 1564 and he lived until he became 77 years old.

Galileo made great contributions to astronomy which paved the way for everything we now know about the Solar System and the Universe. That is why he is considered the Father of Observational Astronomy.

In the past, the term observational astronomy referred to using a telescope to observe objects in the sky and study them. This was different from theoretical astronomy which refers to assuming things about space then looking for ways to prove them right or wrong.

So Galileo was given that name because he was almost the first person to point a telescope toward the sky. Through his telescopic observations, Galileo discovered a lot of things about Venus, Jupiter, Saturn, Neptune, as well as the Moon, our Moon.

After hundreds of years and by using modern technologies, almost all of Galileo’s observations and discoveries turned out correct.

(2) What is Galileo best known for?

Many people are familiar with Galileo because of his brave confrontation with the Roman Catholic Church back in the 17th century. At the time, the world was settled for a space model in which the Earth was the centre of the Solar System. On the other hand, the Sun and all other planets as well as the Moon revolved around the Earth. This model was called the geocentric model or the Ptolemaic system.

The Roman Catholic Church strongly believed in the geocentric model; the Earth was the centre of the Universe. That is why its reaction was pretty harsh when Galileo suggested otherwise.

Through his mathematical work and telescopic observations, Galileo came to the surprising conclusion that it was the Sun that was the centre of the Solar System. He also said that the Earth was just another regular planet among many others that revolved around the Sun; another speck of dust floating in the void of the infinite Universe.

Everyone was shocked and the Catholic Church rejected Galileo’s new space model. They even considered it against religion. 

(3) Did Galileo always want to become an astronomer? 

In fact, no. At least, not at the beginning.

Interestingly, Galileo was apparently hoping to become a musician. His father was a lutenist. The renaissance lute—not flute—was a string musical instrument that pretty much looked like the Middle Eastern Oud.

Galileo’s brother Michelagnolo Galilei became a famous composer and lutenist. Having grown up in such a music-filled atmosphere, Galileo probably hoped to become a musician too. He was even a good lute player himself.

Years went by and Galileo seemed to have lost interest in music. In his youth, he started preparing himself to become a priest. He took it so seriously that he went to study for it at a monastery in a nearby city.

But Galileo’s father disagreed. He wanted his bright son to take a completely different path in life. So he insisted on Galileo enrolling at the school of medicine at the University of Pisa.

Not a lutenist. Not a priest. Galileo was going to become a doctor.

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(4) How did Galileo, then, become an astronomer?

As we have just mentioned, Galileo had given in to his father’s urging and agreed to study medicine. But that was not his fate.

Not long after his enrollment, Galileo left medical school and set off a totally unalike route. He turned to study mathematics after he abruptly fell in love with it all because of, you will not believe it, a chandelier.

One day, Galileo looked up and noticed a chandelier hanging down from the ceiling. It was not still but moving. The chandelier was forced to swing by the air currents. Galileo noticed that it took the same amount of time to travel back and forth.

When he got home, Galileo used two pendulums to repeat the process. He swung one of them at a wide angle and the other at a smaller angle and the same thing happened. Both pendulums took the same amount of time to go back and forth. It was not only that. The pendulum that travelled through a wider range was going faster than the one travelling through a smaller range.

That was the spark. And Galileo went straight ahead to his father and begged to let him study mathematics instead of medicine. While it is not recorded whether or not the father approved his son’s request, Galileo went on anyway to study mathematics as well as natural philosophy and fine arts.

Galileo’s passion and talent for maths and inventions sparked that he began applying what he studied to invent real tools. A few years after he started such studies, Galileo began teaching mathematics in terms of geometry and mechanics at the university. He also taught astronomy.

(5) Did Galileo invent the telescope?

Well, not really. This is one common misconception about Galileo. But he did not invent the telescope. Yet, he upgraded it.

It was a Dutch eyeglass maker named Hans Lippershey who invented the first ever telescope; an apparatus which could magnify far objects. After hearing of it, Galileo made a telescope with a three-time magnifying power. Then, he enhanced it to magnify objects up to 30 times.

This advanced telescope was referred to as the Galilean telescope. At the time, people also referred to it as a spyglass since it spied on objects that were barely, if not never, seen by the naked eye.

Interestingly, Galileo also made a good businessman. After he developed the telescope to a reasonably magnifying power, he sold it to merchants who found the new apparatus pretty useful when sailing at sea.

(6) What did Galileo discover about the Moon?

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In the early 17th century, precisely in 1609, Galileo used his telescope to observe the Moon.

Long before that, people used to think that the Moon was a perfect, smooth, translucent sphere; a pearl hanging in our night sky. This notion was strongly believed by the public as many trusted personalities throughout history supported it.

If the Moon were really so, Its phases would look very smooth throughout the month. But what Galileo saw through his telescope contradicted this perfect sphere theory. He found out that the visible parts of the Moon were uneven. There were small shadows.

Using mathematics and supported by his observations, Galileo discovered that there are mountains and craters on the Moon. He was also able to calculate the height of some of these lunar mountains. This way, Galileo justified the shadows seen on the Moon’s surface and proved it was not as smooth as it was thought to be.

(7) What did Galileo discover about Jupiter?

In early 1610, Galileo made another great astronomical discovery.

Jupiter is easily visible with the naked eye in a clear night sky. So it was not much of a big deal when Galileo observed it. What was revolutionary was viewing Jupiter’s moons.

Using his more advanced telescope, Galileo was able to view three incredibly small objects near the largest planet. At first, he thought they were fixed stars. Fixed stars are so distant that their motion can only be detected when observed over a long period of time. In other words, fixed stars look fixed, motionless, in the sky. So that is what Galileo thought of those three dots near Jupiter.

But on the next night, Galileo found out that those ‘fixed’ stars changed their positions relative to Jupiter. That meant they were not fixed stars but rather something else. After a few observations and the discovery of one more of these objects, Galileo concluded that these four objects were orbiting Jupiter. They were Jupiter‘s moons. 

Galileo named these four moons after the Italian duke Cosimo II de’ Medici and his brothers. The reason for that is most probably gratitude. In 1610, Cosimo lawfully helped Galileo have more freedom in teaching mathematics at universities. Maybe that is how Galileo thought he could pay Cosimo back since it was ‘mathematics’ that contributed to discovering Jupiter’s moons.

Interestingly, Galileo was not the only astronomer observing the sky through a telescope. Many other astronomers were also pointing their telescopes at the sky and studying it. On the same night when Galileo discovered the Jovian satellites were moving, another German astronomer also observed the four moons of Jupiter!

(8) What reaction did the discovery of Jupiter’s moons spark?

The discovery of Jupiter’s moons was pretty much revolutionary. It can also be fairly described as controversial. Here is why.

Aristotle was one of the greatest and most influential philosophers ever lived on Earth. He was Greek and he lived almost a millennium before Galileo observed Jupiter’s moons. 

Despite his great contributions to science and philosophy, Aristotle was a human being after all. He was prone to making mistakes. For instance, he strongly believed in the geocentric model in which the Earth was the centre of the Universe. Thanks to Aristotle’s integrity, the large masses and later the Catholic Church believed in the geocentric model too, for centuries.

So when Galileo discovered there were four natural satellites orbiting Jupiter and not the Earth, many astronomers refused his idea. They thought Galileo must have been mistaken about something. German Astronomer Christopher Clavius was one of the few who believed Galileo because he also observed Jupiter’s moving moons.

This observation would go on and assist other discoveries by Galileo to become the cause for his unfair imprisonment later on.

(9) What did Galileo find out about Venus?

Through his telescopic observations, again, Galileo found out that Venus, the brightest, hottest, and second-closest planet to the Sun, had phases. These phases looked similar to the phases of the Moon.

The mere happening of these phases suggested that Venus must be orbiting the Sun and not the Earth. This was another point that ditched Aristotle’s claim of the Earth being the centre of the Universe.

(10) Did Galileo have any further Solar System observations?

He sure did. 

Like Jupiter, Saturn is always bright and visible in a clear night sky, after 10:00 pm, usually in the southeast. It has been viewed by our ancestors for thousands of years. With the naked eye, Saturn appeared like a bright dot and nobody knew anything about its rings. That was until Galileo aimed his telescope at the ringed planet in 1610.

When Galileo saw Saturn‘s rings, he could only see two small elliptical objects on each side of the planet. So he thought they were parts of it; that Saturn was a three-bodied object.

Sometime later, Galileo observed Saturn again and the attached bodies were invisible. He thought they disappeared. That happened because the Earth was on the same plane as Saturn. So the rings were perfectly horizontal to the observer on the Earth. That is why they looked as if they disappeared. 

This existence/non-existence of what he thought were twin bodies confused Galileo. Because he lacked a more advanced telescope, Galileo was not able to know what those Saturn bodies were. Despite that, he was the first to observe them and therefore receive credit for their discovery. 

It was not until 1655 that a Dutch astronomer named Christiaan Huygens using a much more advanced telescope could see and identify the true shape of Saturn’s rings.

In 1612 and 1613, Galileo also observed Neptune, the outermost planet of the Solar System. But again, just like what happened with Saturn, Galileo could not identify Neptune clearly. So he thought it was just a fixed star.

That said, Galileo recorded the position of Neptune in some drawings. More than two centuries later, a German astronomer called Johann Gottfried Galle could observe Neptune more clearly than Galileo did. According to Galle’s observation, the position of the blue planet was almost the same as that previously identified by Galileo. 

So technically, Galileo was the first to observe Neptune even though he did not know what it was.

In the years to come, Galileo would make many other observations about the Solar System and the Milky Way. Such discoveries were as thorough as they were contentious. They helped reveal the truth about how the Universe was operating. But they also contributed to sentencing the genius astronomer to life imprisonment.

(11) How was Galileo’s trial?

As we have mentioned earlier, many of the astronomical observations that Galileo made contradicted the geocentric model. On top of these discoveries were the phases of Venus and Jupiter’s moons. These findings proposed that planets must be revolving around the Sun and not the Earth. This model was called heliocentrism or the heliocentric model.

Interestingly, Galileo was not the first to propose the heliocentric theory. It was suggested more than 70 years earlier by another Italian astronomer called Nicolaus Copernicus.

The Catholic Church strongly adopted the geocentric theory. That is why it strongly opposed Galileo’s findings. It even went on and declared heliocentrism as unorthodox, completely heretical. That was in 1616.

Up until that time and a decade later, Galileo was free to continue his findings as no official condemnation was made against him. So he went on to propose the theory of tides which attributed them to the Earth’s motion; another thing that contradicted geocentrism.

After that Galileo wrote a book called Dialogue Concerning the Two Chief World Systems comparing geocentrism and heliocentrism. As you might have guessed, he defended heliocentrism in that book.

The book was published in 1632. Soon after its publication, it became widely popular. Such popularity was viewed as a threat by the Catholic Church. So the Roman Inquisition, which was a powerful office set by the Catholic Church to punish those found guilty of heresy, arrested Galileo and sent him to trial.

The judges strongly found Galileo suspect of heresy. As a result, Galileo was banned from teaching anything that would defend heliocentrism. He was also sentenced to life imprisonment at his home. Galileo never left his home after the trial in 1633 except for his grave in 1642. He died at the age of 77.

(12) How did the modern astronomical society pay tribute to Galileo?

With more technological advancements in astronomy, many of Galileo’s observations proved to be correct. Even most of his observations were somewhat accurate despite the not-that-advanced equipment he used back in the 17th century.

Having discovered that Galileo was right, the modern astronomical society wanted to honour him and free him from the unfaithful accusations. One way to do that was to rename Jupiter’s moons after him.

As a group, the four largest Jovian moons Galileo discovered are called the Galilean satellites. Individually, they are called, largest to smallest, Ganymede, Callisto, lo, and Europa. 

In addition, a spacecraft developed by NASA bore the name Galileo. It was intended to study Jupiter and its moons. Galileo was launched in October 1989 on Space Shuttle Atlantis.

The spacecraft was estimated to take 8 years and 1.5 months to reach Jupiter’s orbit. But it could successfully do so in only 7 years and 9.5 months, precisely entering Jupiter’s orbit on December 7th 1995.

Galileo orbited Jupiter and closely studied it as well as its four largest moons, the Galilean moons. Surprisingly, Galileo found evidence of liquid salt water underneath the thick sheets of ice on three of the Galilean moons. Such a discovery suggested the possibility of the existence of any lifeform on Jupiter’s moons.

Galileo also provided information about thunderstorms on Jupiter which were much, much larger than those happening on the Earth.

After spending nearly 14 years in space, Galileo’s mission ended on September 1, 2003. So NASA deliberately crashed the spacecraft into Jupiter. The scientists chose such a tragic ending because they feared if Galileo had been left in orbit, it may have collided with one of the Galilean moons. Such a collision was surely to contaminate any lifeforms scientists believed might have existed on these moons.

In February 1910, German Astronomer J. Helffrich discovered an asteroid orbiting the Sun. The asteroid is as big as a minor planet. It was named 697 Galileo in honour of Galileo.

In addition, American Astronomers Geoffrey Marcy and R. Paul Butler discovered a giant gas planet In April 1996. The planet is blue and is around 80% the size of Jupiter. It orbits another star that is 41 lightyears away from our Sun—one light year is 9.5 trillion km! This planet was called Galileo, again in honour of the great Italian astronomer.

Another thing that honoured Galileo was naming the year 2009 the International Year of Astronomy. This year was the 400th anniversary of the first time Galileo aimed his telescope at the sky, marking the birth of modern science and astronomy.

In the early 20th century, a museum was dedicated to Galileo Galilei, Museo Galileo, in Florence, Italy. Hosted in an 11th-century building, Galileo’s museum contains a large collection of Galileo’s scientific instruments which he invented himself. After some renovations, the museum has been welcoming visitors since 2010.

(13) Did the Vatican ever change their mind about Galileo?

Sadly, not until 1992!

The Roman Catholic Church, which was later given the Vatican City and accordingly referred to as the Vatican, had apparently clung to their accusation of Galileo for a tremendous period of time, around 359 years!

After innumerable great advancements in astronomy that proved Galileo’s findings were absolutely right, Pope John Paul II of the Vatican started an investigation to look into Galileo’s old accusation. That was in 1979. After 13 years, in 1992, the investigation concluded that the court had made a mistake by sending Galileo to trial. So a formal apology was made to him.

The laws of motion developed by Sir Isaac Newton explain the connection between a physical object and the forces that act upon it. By understanding this information, we can construct the foundation for modern physics.

Newton's laws of motion
laws of motion

 Newton’s laws of motion are three laws that explain how objects move in response to applied forces. They were first published in 1687 and have since become fundamental principles in physics.  And considered laws Isaac Newton, an English mathematician and physicist, is credited with being the first person to formulate. The relationship between the forces acting on the body and the motion of the body. 

These relations are the basis of classical mechanics and are described here.

Newton’s First Law States that :

If a body is resting or moving in a straight line at a constant speed, it will continue to do so unless a force acts upon it. 

If a force acts upon it, it will change its speed or stop moving in a straight line altogether. In fact, In classical Newtonian mechanics, there is no significant difference between rest and linear motion. Stationary and constant-velocity motion in a straight line can be considered the state of motion seen by another observer in which one observer is moving. 

One moves at the same speed as the particle and the other moves at a constant velocity relative to the particle.  In other words, rest and uniform motion in a straight line are regarded as the same state of motion. 

The concept behind this postulate is referred to as the Law of inertia.

Galileo Galilei was the one who initially conceptualised the Law of Inertia of Horizontal Motion on Earth.

René Descartes was the one who went on to generalise the concept. To the untrained eye, the principle of inertia may not appear as intuitively obvious as the starting point and basic assumption of classical mechanics. An object that is not pushed tends to rest, according to Aristotelian mechanics and also according to everyday experience.

Galileo’s experiments with balls rolling down inclined planes provided the basis for his derivation of the Law of inertia.

For Galileo, the principle of inertia was essential to the completion of his primary scientific endeavour, which required him to explain how it was possible for us to be unaware of the motion of the Earth, despite the fact that it was rotating on its axis and moving around the Sun. 

You can use the concept of inertia to find the answer given that we are moving along with the Earth and that our inclination is to keep moving in the same direction; Earth appears to be still to us even though we are moving. Therefore, the principle of inertia, which is not a statement of the obvious, was at one time the primary focus of debate in the scientific community.

Newton was able to accurately calculate small deviations due to the non-uniform movement of the Earth’s surface in a straight line.  Newton’s discovery that the motion of the Earth’s surface is not a constant motion in a straight line made this outcome conceivable.

The widespread observation that unforced bodies have a tendency to return to their resting positions is attributed to the fact that, according to the Newtonian formulation, to the fact that these bodies have forces acting on them that are unbalanced, such as friction and air resistance. This is a common observation.

Example of Newton’s First Law of Motion in Everyday Life 

Newton's laws of motion
The first Law of motion

If you jump out of a moving car or bus,  the ground exerts an effect on your feet, and your feet become immobile. You are going to fall because the top half of your body did not stop moving, and you will fall in the same direction you were going in before. – If there is no external force acting on a stationary object, then the object will not move.

– A moving object will continue to move even in the absence of any external forces…

Newton’s second Law – laws of motion: F = ma

The second laws of motion
Newton's second law
the force applied to a body produces a proportional acceleration – Newton’s second Law presented with sticky notes and white chalk handwriting on a blackboard

Newton’s Second Law:

 It is a quantitative description of the change in motion of a body due to a force. The rate of change with time of the direction and magnitude of an object’s momentum is equal to the force exerted on the object. The angular momentum of an object equals its mass multiplied by its velocity.

Momentum, like velocity, is a vector quantity that has both magnitudes. And direction. A force acting on the body can change the magnitude or direction of the impact or both. One of the most important laws is Newton’s Second Law, one of the laws of motion in all physics. An object of constant mass m can be written as F = ma. 

Where both force (F) and speed (a) are vector quantities.

An object with a net force will accelerate according to the Second Law. It is assumed that there is no net force acting on the body either because there is either no force or the opposite force balances all forces. The body will then be in equilibrium without acceleration. Instead, we can conclude that an object with inertia has no net force.

Example of Newton’s Second Law of Motion in Everyday Life 

As we know of the laws of motion, According to Newton’s Second Law of Motion, acceleration, or the process of picking up speed, takes place whenever a force is applied to a mass (object). Riding a bicycle is a great demonstration of how this Law of motion works in practice. The mass is represented by your bicycle. The force is provided by your leg muscles as they push down on the pedals of your bicycle.

Newton’s third law: F = G(m1m2)/R2

The Third law of motion
Gravity vector illustration. Explained natural force to objects with mass—basics of universe physics. Gravitation gives weight to physical spacetime: Newton’s law formula, universe and apple example.

The most famous laws of Newton are the laws of motion (Third Law, action and reaction)

Newton’s Third Law states that when two objects interact, equal and opposite forces act on each other. The third Law is also called the Law of action and reaction. 

This Law is important in the analysis of static equilibrium problems where all forces are in equilibrium, but it also applies to objects in uniform or accelerated motion. 

The power it describes is real, not just a calculating tool.

 For example, a book placed on a table exerts a downward force equal to the table’s weight. 

According to the third Law, the tables give the cards equal and opposite forces.

 This force causes the table to deform slightly under the weight of the book, pressing the book like a spring.

An object with a net force will accelerate according to the second Law of the laws of motion. An object can be in equilibrium without acceleration if there is no force acting on it, either because there is no force at all or because opposing forces exactly balance all forces. 

Conversely, we can conclude that an object found to have no acceleration has no net force.

Example of Newton’s Third Law of Motion in Everyday Life 

The third laws of motion
Newton’s 3rd Law. The mutual actions of two bodies upon each other are always equal and directed to contrary parts.

It asserts, “There is an equal and opposite reaction to every action.”

The force that the first object exerts on the second when two objects interact is referred to as action. The reaction force is the force that the second body exerts on the first. Therefore, the action and its equal and opposite reactions are of equal magnitude.

Examples based on Newton’s third Law, one of the laws of motion.

– When a bullet is fired from a gun, the gun imparts a force that propels the bullet forward. In reverse, the bullet exerts an equal amount of force on the rifle.

An open book on a table: On the table, the weight of the books is exerting a downward force (action). While the reaction affects the books in an upward direction,

-When you jump, the force of your legs striking the ground causes the ground to respond by applying a force equal and opposite to the first, which launches you into the air.

– During swimming, the swimmer advances. As the swimmer pushes against the water, the water pushes back on the swimmer.

Influence of Newton’s laws

Effect of Newton’s Law

  • Newton’s laws first appeared in his masterpiece Principia Mathematica (1687). 
  • And are also known as “Principles”. In 1543, Nicolaus Copernicus proposed that the Sun could be the centre of the universe instead of the Earth. Meanwhile, Galileo, Johann Kepler, and Descartes replaced the Aristotelian worldview inherited from ancient Greece and laid the foundation for a new science explaining the workings of the heliocentric universe. 
  • In the Principia, Newton created a new science. He was able to develop his three laws. Explain that a planet’s orbit is an ellipse, not a circle, but as a result, it explains much more. 
  • The sequence of events from Copernicus to Newton is called a scientific revolution.

 And R divided by the square of the distance: F = G(m1m2)/R2.

Isaac Newton proposed this Law in 1687 and used it to explain the observed movements of the planets and the moon. 

  • It was formulated mathematically by Johannes Kepler in the early 1600s.
  • All three of Newton’s laws apply to objects regardless of their size or whether or not they are made of different materials. 
  • This fact makes them useful when modelling objects of various sizes and compositions because they can be applied uniformly across all objects. 

There are some exceptions:

– Newton’s laws do not apply in some situations, such as when an object is moving close to the speed of light.

 – In addition, they do not apply when dampening forces oppose the motion, such as friction or air resistance. For this reason, these laws should be interpreted with care and applied carefully when modelling the motion of objects.

– Many people believe that Newton’s First Law does not apply in some cases for beginners. 

This is because many things that happen in daily life occur without being pushed, such as objects falling due to gravity.

 – In addition, many people believe that this Law does not apply because objects at rest can also be pushed by other forces, such as wind or water currents.

– In general, many people believe this Law does not apply because there are many forces at work other than gravity.

– Others believe that Newton’s Second Law does not apply in some cases to advanced students. This is because many students do not know their mass or how to measure their acceleration due to gravity.

– In addition, many students do not know how to calculate force, which makes it difficult to understand Newton’s Second Law. 

This makes it difficult for many students to apply Newton’s second Law in everyday life.

– Some believe that Newton’s Third Law does not apply in some cases to everyone.

 This is because many people believe that this Law does not apply when considering human interaction or moral responsibility.

 In addition, some people believe that it does not apply when considering projectiles and explosions because they occur in different directions.

Some people do not agree with Isaac Newton’s laws of motion and gravity because they are controversial and open to interpretation.

 For example, some disagree with his laws because they do not apply in all situations and can be difficult to interpret accurately. Others disagree with his laws because they do not agree with his interpretation of gravity and motion.

Ultimately, Isaac Newton’s laws of motion are universally accepted because they are useful for modelling the motion of objects under the influence of applied forces. 

However, there are some exceptions because these laws can be difficult to interpret accurately and difficult for beginners to understand. 

Therefore, it is important to understand what these laws mean before applying them since they can also be difficult for advanced students to understand.

If you check the last details we provided, you will find that you have the necessary basic information about Newton’s laws of motion. Keep on visiting Learning Mole to learn a lot more about everything out there.

The universe around us

The universe is very old and tremendously gigantic. It extends in all directions for long distances measured by big units called light-years. A light-year is defined as how far light travels in one year. Since the speed of light is 300,000 km/sec, one light year is 9.5 trillion km (that is a very very long distance!)

This enormous space is full of galaxies. Galaxies are full of millions and millions of stars. Each star is a big ball of fire with a powerful gravitational force. This force pulls other space bodies and makes them orbit the star.

We happened to live on top of one of these objects called Earth which orbits a star called the Sun. Many other objects orbit the Sun as well. Scientists then categorized all these objects in one group called the Solar System (sol means sun in Latin).

planets of the solar system

The Sun is the most gigantic object in our Solar System. It comprises 98% of the Solar System’s mass. The remaining 2% of the mass is occupied by all the planets, dwarf planets, moons, asteroids, and comets spinning around the Sun.

Some of these objects, like planets, orbit the Sun directly in almost circular or elliptical orbits. Other objects orbit the Sun indirectly like natural satellites, also known as moons. These moons orbit planets or comets which in turn orbit the Sun.

But how did the Solar System form?

How did planets form?

Well, that is a really interesting story so read closely.

In space, the matter and radiation between star systems are called interstellar medium. A thick region of the interstellar medium that accumulates gas, plasma, and dust is called an interstellar cloud. There are different types of interstellar clouds. One of them is called a molecular cloud.

About 4.6 billion years ago, a giant molecular cloud of hydrogen and helium collapsed. This collapse caused all the mass, which was too hot, to be collected in the center forming the Sun.

In addition, this collapse produced so much dense gas and dust that formed a disc around the Sun. These gassy and dusty particles started to be attracted to one another by gravitational power to form bigger bodies.

Such bigger bodies were later categorized as planets, dwarf planets, asteroids, comets, and moons. There are eight planets in our Solar System. Scientists further classified these eight as inner system planets and outer system planets.

Inner system planets VS outer system planets

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The inner system planets are the four closest planets to the Sun. They are also referred to as terrestrial or rocky planets. These planets are Mercury, Venus, Earth (hello!), and Mars. All of them are composed of silicate rocks or metal.

The outer system planets are also four but gigantic and mostly composed of gas and ice. The largest of the four are Jupiter and Saturn. They are called gas giants because they are composed of hydrogen and helium.

The second-largest ones are Uranus and Neptune. They are so far from the Sun that they are unusually cold. They are composed of ice, not only water ice but also ice of ammonia and methane. And just like the sky makes the ocean look blue, methane also makes those two distant planets blue.

Since it was discovered in 1930 until the early 21st century, Pluto was considered a planet. It was the ninth planet of the Solar System after Neptune. Yet, scientists discovered many other objects. They were either the same size as or bigger than Pluto. So in 2006, the International Astronomical Unit reclassified Pluto as a minor or a dwarf planet.

The inner system planets are the four closest planets to the Sun. They are also referred to as terrestrial or rocky planets. These planets are Mercury, Venus, Earth (hello!), and Mars. All of them are composed of silicate rocks or metal.

The outer system planets are also four but gigantic and mostly composed of gas and ice. The largest of the four are Jupiter and Saturn. They are called gas giants because they are composed of hydrogen and helium.

The second-largest ones are Uranus and Neptune. They are so far from the Sun that they are unusually cold. They are composed of ice, not only water ice but also ice of ammonia and methane. And just like the sky makes the ocean look blue, methane also makes those two distant planets blue.

Since it was discovered in 1930 until the early 21st century, Pluto was considered a planet. It was the ninth planet of the Solar System after Neptune. Yet, scientists discovered many other objects. They were either the same size as or bigger than Pluto. So in 2006, the International Astronomical Unit reclassified Pluto as a minor or a dwarf planet.

And then what?

In fact, there are many other bodies in the Solar System. They might not be as large as planets but definitely as marvelous. For example, asteroids.

Asteroids

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Besides the eight known planets, there are many, so many that we cannot even count them, other smaller rocky bodies called asteroids. They are not round but they have irregular shapes.

Asteroids can be very large or very small. For example, the diameter of the largest asteroid ever found, Vesta, is 525 km. That is almost the distance between London and Belfast! However, the smallest asteroid scientists discovered is about 10 meters across.

The largest collection of asteroids in our Solar System, about 1.1 to 1.9 million, is found in the space between Mars and Jupiter. This collection is defined as the asteroid belt. These millions of asteroids orbit the Sun too.

Just like the asteroid belt, there is the Kuiper belt right behind the orbit of Neptune. This Kuiper belt is different from the asteroid belt. Its objects are mostly composed of ice because they are very very far from the Sun. Pluto in fact lives in the Kuiper belt along with many similar brothers of objects.

Besides the eight known planets, there are many, so many that we cannot even count them, other smaller rocky bodies called asteroids. They are not round but they have irregular shapes.

Asteroids can be very large or very small. For example, the diameter of the largest asteroid ever found, Vesta, is 525 km. That is almost the distance between London and Belfast! However, the smallest asteroid scientists discovered is about 10 meters across.

The largest collection of asteroids in our Solar System, about 1.1 to 1.9 million, is found in the space between Mars and Jupiter. This collection is defined as the asteroid belt. These millions of asteroids orbit the Sun too.

Just like the asteroid belt, there is the Kuiper belt right behind the orbit of Neptune. This Kuiper belt is different from the asteroid belt. Its objects are mostly composed of ice because they are very very far from the Sun. Pluto in fact lives in the Kuiper belt along with many similar brothers of objects.

So, what did our ancestors think about the Solar System?

Galileo Galilei LearningMole

Since the beginning of life on Earth, humans have been interested in exploring space. Ancient civilizations like Egypt and Babylon studied the stars and planets. They took measurements to determine festivals and the hours of the night.

However, people throughout history always believed that Earth was the center of the universe. They imagined it floating motionless while other planets and stars spun around it.

Perhaps one of the earliest true assumptions ever made about the Solar System was that by the ancient Greek mathematician and astronomer Aristarchus of Samos (born in 310 BC). He presented a model that placed the Sun in the middle while Earth and other space objects revolved around it.

Unfortunately, Aristarchus was not believed much. This is because other great philosophers such as Aristotle thought he was wrong. And since the public extremely trusted Aristotle, they did not believe Aristarchus as well.

Starting the 15th century, many astronomers and mathematicians from different regions across Europe began to explore the sky, planets, and stars. They developed different theories that later proved Aristarchus right.

It is so interesting to mention here that all these incredibly intelligent astronomers made their assumptions about the Solar System mostly by using mathematics. They barely looked at the sky. Well, even if they did, they would only see teeny-tiny twinkling bulbs and nothing more.

And this is when telescopes came into existence.

The story of telescopes

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In 1608, a Dutch eyeglass maker invented an instrument that could magnify objects three times. A year later, an Italian astronomer—who would become very known after that—heard about this invention. So he made one for himself that could magnify objects 20 times.

This Italian astronomer was Galileo Galilei. Because he was so interested in space, Galileo started pointing his 20-time magnifying optical instrument towards the sky. Later on, this instrument took the name of the telescope.

Using his telescope, Galileo could make different observations of objects in the sky. For example, he observed Earth’s moon and the transits of Venus. He also discovered that Jupiter, the biggest planet in our Solar System, had four moons.

Galileo then used these observations to claim that the Sun was the center of the Solar System, not Earth and that all other planets orbited it.

But once again, Galileo was not believed; this time by the Catholic Church as well as thousands of people. Those people only accepted the model in which Earth was at the center of the sky. So, the Church considered Galileo’s model against religion.

Sadly, Galileo was arrested and kept in his house as a prisoner. Nine years after his arrest, he died.

Luckily, Galileo’s observations did not die with him. Many astronomers followed in Galileo’s footsteps. They could prove mathematically and telescopically that the Sun is in the middle and that other planets and sky bodies orbit it. This fact was later given the name we are all familiar with: the Solar System.

How were planets discovered?

So far, we have learned about the Solar System as a whole. We understood what our ancestors thought about it. We also found out how the great astronomers of the past proved the Sun is in the middle of the sky.

Now let’s learn about how each planet was discovered.

Mercury and Venus are two planets that can be spotted in the sky with the naked eye. Ancient people knew about and mentioned them in their rocky journals. But Galileo (remember him from above?) was the first person to observe both Mercury and Venus through a telescope. That was in the early 17th century.

During the next two centuries, many other astronomers could observe both planets using more accurate telescopes. Such observations enabled them to study Mercury’s surface features and Venus’s phases and atmosphere. Astronomers could also calculate Mercury and Venus’s day and year lengths.

Mars, Jupiter, and Saturn were also known in prehistoric times. Galileo (yes, again) could observe Mars with his telescope in 1610. In the same year, Galileo observed the four largest moons of Jupiter. These moons, as a group, were named after him: Galilean moons.

Yet, Galileo’s simple telescope could not observe Saturn accurately. But in 1655, a Dutch astronomer called Christiaan Huygens using a more advanced telescope saw Saturn’s rings and one of its moons.

So far, we have learned about the Solar System as a whole. We understood what our ancestors thought about it. We also found out how the great astronomers of the past proved the Sun is in the middle of the sky.

Now let’s learn about how each planet was discovered.

Mercury and Venus are two planets that can be spotted in the sky with the naked eye. Ancient people knew about and mentioned them in their rocky journals. But Galileo (remember him from above?) was the first person to observe both Mercury and Venus through a telescope. That was in the early 17th century.

During the next two centuries, many other astronomers could observe both planets using more accurate telescopes. Such observations enabled them to study Mercury’s surface features and Venus’s phases and atmosphere. Astronomers could also calculate Mercury and Venus’s day and year lengths.

Mars, Jupiter, and Saturn were also known in prehistoric times. Galileo (yes, again) could observe Mars with his telescope in 1610. In the same year, Galileo observed the four largest moons of Jupiter. These moons, as a group, were named after him: Galilean moons.

Yet, Galileo’s simple telescope could not observe Saturn accurately. But in 1655, a Dutch astronomer called Christiaan Huygens using a more advanced telescope saw Saturn’s rings and one of its moons.

What about Uranus?

Just like his planetary neighbors, Uranus was observed in prehistoric times but it was mistaken for a star. Then in the late 17th century and the mid 18th century, multiple astronomers observed Uranus at least 18 times.

One day in March 1781, British astronomer Sir William Herschel was observing the sky from his garden. Using his telescope, he spotted an object. At first, he thought this object was either a Nebulous star or a comet. But he later defined it as a comet. Then again, Herschel thought that the object he discovered was either a comet or a planet.

Later, Finnish-Swedish astronomer Anders Johan Lexell discovered that the new object had a nearly circular orbit, like planets. But comets have an overly elliptical orbit. So the new object was internationally identified as a planet.

Just like his planetary neighbors, Uranus was observed in prehistoric times but it was mistaken for a star. Then in the late 17th century and the mid 18th century, multiple astronomers observed Uranus at least 18 times.

One day in March 1781, British astronomer Sir William Herschel was observing the sky from his garden. Using his telescope, he spotted an object. At first, he thought this object was either a Nebulous star or a comet. But he later defined it as a comet. Then again, Herschel thought that the object he discovered was either a comet or a planet.

Later, Finnish-Swedish astronomer, Anders Johan Lexell discovered that the new object had a nearly circular orbit, like planets. But comets have an overly elliptical orbit. So the new object was internationally identified as a planet.

And Neptune?

We learned that Galileo observed Mercury, Venus, Mars, and Jupiter. He also spotted Neptune with his telescope. Galileo observed Neptune twice on 28 December 1612 and on 27 January 1613. However, he did not think it was a planet. He thought it was a stationary star.

One day in 1821, the French astronomer Alexis Bouvard published astronomical tables about Uranus’s orbit. Such tables contained data that facilitated the calculation of Uranus’s position and its planetary calendar.

However, when Bouvard observed Uranus with a telescope, he saw something strange. Uranus’s orbit experienced some changes. These changes caused the orbit to deviate from the perfect circle shape. That meant Bouvard’s data and the real data from the orbit were unmatching.

So Bouvard assumed that Uranus was subject to gravitational force from a mysterious planet. More than 20 years later, two other astronomers called John Couch Adams and Urbain Le Verrier used Bouvard’s observations to predict, with mathematical calculations, the position of that mysterious planet.

In September 1846, German astronomer Johann Gottfried Galle was able to observe Neptune using an advanced telescope. His observation almost matched the calculations made by Urbain Le Verrier.

It is interesting to mention here that Galileo recorded his observations as drawings. In them, there were some plotted points in a position. When Galle later discovered Neptune, he found out that those dots in Galileo’s drawing were in the same position as that of Neptune.

Galileo was the first to observe Neptune but he never knew that.

How did planets get their names?

Now we are quite familiar with the concept of the Solar System and its second most popular inhabitant, the planets. We learned about how and by whom they were discovered. Now let’s discuss how each planet got its name. There are some interesting stories so let’s take them one by one.

Mercury

Before Mercury became the name of the closest planet to the Sun, it was the name of a Roman god which people worshiped many many centuries ago. The god Mercury was actually a messenger. He could travel very quickly delivering messages from here to there among other gods.

On the other hand, Mercury, the planet, is the fastest in the Solar System. Being very close to the Sun means the planet is subject to a huge gravitational pull. This pull in return causes the planet to orbit the Sun very fast. In fact, Mercury travels around the Sun in only 88 days. That is even shorter than winter in Ireland!

So, the fastest planet was named after the fastest Roman god, Mercury. Makes sense.

Before Mercury became the name of the closest planet to the Sun, it was the name of a Roman god which people worshiped many many centuries ago. The god Mercury was actually a messenger. He could travel very quickly delivering messages from here to there among other gods.

On the other hand, Mercury, the planet, is the fastest in the Solar System. Being very close to the Sun means the planet is subject to a huge gravitational pull. This pull-in return causes the planet to orbit the Sun very fast. In fact, Mercury travels around the Sun in only 88 days. That is even shorter than winter in Ireland!

So, the fastest planet was named after the fastest Roman god, Mercury. Makes sense.

Venus

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With Venus, things start to get a little different (and interesting.)

Although Mercury is closer to the Sun, Venus is much hotter. In fact, Venus is hotter than any other planet in the Solar System. This is because Venus is covered in clouds and its very thick atmosphere is full of carbon dioxide. This gas creates the well-known greenhouse effect. Such an effect keeps the heat inside and prevents it from escaping to space.

In addition, these clouds reflect the light coming from the Sun. That is why Venus always looks as bright as the Moon. But Venus looks tinier than the Moon of course because it is further from Earth.

As Venus is so beautifully bright, well the brightest of all planets, it was given the name of the Roman goddess of beauty and love. Interestingly, Venus can be seen with the naked eye to the east before sunrise or in the west during the evening.

Earth

Earth, also known as home.

When it comes to naming Earth, we do not really seem to know a lot about it. All we know is that the word earth came from English/German origins which means the ground.

Maybe because it is the only planet suitable for life?

Mars

Way before Mars referred to a 51g-nougat-caramel-almondless chocolate bar, it was the name of the Roman god of war.

Meanwhile, planet Mars was found to be red. Scientists attributed its red color to the fact that Mars’s surface is full of iron oxide. Iron oxide is a red chemical composed of iron and oxygen. It gives Mars the red color. It is also the same chemical that gives blood and rust their reddish color.

Since blood is associated with war, the fourth planet from the Sun was then named after the Roman god of war, Mars.

Jupiter

Jupiter is the giant of the giants and the second biggest body in the Solar System. It is so big that it is 11 times wider than the earth. To easily get that, imagine a coin is Earth then place 11 such coins beside one another. They would make the diameter of a much bigger circle. This bigger circle is Jupiter.

Naming Jupiter was no big deal at all. The gigantic planet got its name from the Roman king of gods, Jupiter, who was in charge of all aspects of life in Roman religion.

Saturn

Known for its incredibly beautiful rings, Saturn is the second biggest planet after Jupiter. It is also the third biggest body in the Solar System. Saturn got its name from Roman mythology. It was named after the Roman god of wealth, agriculture, and harvest.

Uranus

We learned that Sir William Herschel was the astronomer who discovered Uranus. And just like we get to name a kitten we adopted, Herschel was asked to name the planet he discovered. So he named it after King George III who ruled Britain back at the time.

Yet, such a name was only popular in Britain and not in the rest of the world. So many other names were then proposed. But seventy years later, the seventh planet in the Solar System was finally given the name of Uranus. Uranus was the Greek god of the sky.

Neptune

Neptune is often described as Uranus’s near-twin. It is the eighth planet in the Solar System. Neptune is also the bluest, densest, and furthest planet from the Sun.

Naming Neptune is an interesting story to know. At first, it was called the planet exterior to Uranus or Le Verrier’s planet. Then astronomers began suggesting different names such as Janus and Oceanus. These were Roman and Greek gods’ names.

Neptune was known to be the god of the sea in Roman religion. Astronomers wanted to keep with the previously named planets in the Solar System. That is why they called the eighth planet Neptune.

How many orders can we put planets in?

We are now familiar with the planets in our Solar System. We learned about how planets were discovered and how they got their names. We also learned some interesting facts about planets such as Venus’s brightness.

By default, planets are classified according to their distance from the Sun. This order goes like this: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. Yet, we can also arrange planets in order of heat, size and mass, orbital speed, and day length. Let’s explore them one by one.

Planets in order of heat

It is very rational to think that the closer a planet is to the Sun, the hotter it is. But this does not apply to two of the planets in our Solar System: Venus and Uranus.

As we previously explained, Venus’s atmosphere is full of carbon dioxide. This gas keeps the heat inside and prevents it from escaping to space. This makes Venus hotter than any other planet in the Solar System.

Similarly, we would think that Neptune is colder because it is further from the Sun than Uranus. In fact, it is the other way around. The coldest temperature ever found on Uranus was -223.8 °C which beats Neptune’s coldest temperature -210 °C. Here is how this happens.

Every planet has an axis. Scientists found that each planet also tilts a certain degree. While Earth’s tilt is 23 degrees, Uranus’s tilt is 98 degrees! This makes Uranus look like it has been knocked over and is rotating on its side.

This tilted rotation is believed to cause Uranus to never retain the heat coming from its core. It escapes perpetually to space. This causes Uranus to be very cold, even colder than its brother Neptune.

So when we put planets in order of heat, they go like this: Venus, Mercury, Earth, Mars, Jupiter, Saturn, Neptune, and Uranus.

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Planets in order of size

This is another order when planets take different positions than that of the distance from the Sun.

Mercury happens to be the smallest planet in the Solar System with a radius of 2.4 km.

The second smallest planet is Mars with a radius of 3,389.5 km. Scientists believe that Mars has become so small because of the gravitational pull of Jupiter, its giant neighbor. Jupiter’s gravity caused Mars’s small size while it was forming billions of years ago.

Some planets are very close in size like Venus with a diameter of 6,051.8 km and Earth with a diameter of 6,371 km. It is the same case with Uranus, 25,362 km in radius, and Neptune, 24,622 km in radius. Each pair of these planets is called near-twins.

Now, putting planets in order of their size would come up this way: Mercury, Mars, Venus, Earth, Neptune, Uranus, Saturn, and Jupiter. This is also the same planet arrangement in order of mass.

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Planets in order of orbital speed

Orbital speed is how fast a planet orbits the Sun. Every object in the Solar System is attracted to the Sun by its gravitational pull. That means, the closer an object is to the Sun, the stronger the Sun’s gravitational pull. This also means that the stronger the gravitational pull on a planet, the faster the planet revolves around the Sun.

Such orbital speed also determines how long a planet takes to complete one orbit around the Sun. This is called the solar year. So when a planet is fast, it takes a short time to orbit the Sun. So, fast planets have short solar years, and vice versa.

That is why Mercury is the fastest planet with an orbital speed of 47.36 km/s. Mercury also has the shortest solar year of 88 earth days. Likewise, Neptune is the slowest planet. It goes around the Sun at a speed of 5.43 km/s. That is why Neptune’s solar year is the longest. It is equal to 60225 earth days (Earth’s solar year as you know is 365.25 days)

So, planets in order of their orbital speed are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. This is also the same planet arrangement when put in order of their distance from the Sun.

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Planets in order of day length

Three paragraphs ago, we defined a solar year as the period taken by one planet to complete one revolution around the Sun. A planet takes one whole day to complete one rotation around its axis.

And this is where the fun begins! When it comes to putting planets in order of their day length, things get a little jumbled. For example, Jupiter completes one rotation around its axis in only 10 hours. Then comes Saturn with 10 hours and 42 minutes, Neptune with 16 hours and 6 minutes, and Uranus with 17 hours and 14 minutes.

We know that Earth’s day lasts 24 hours. That means the giant planets of the Solar System have shorter days than that of Earth. In sixth place, we have Mars with 24 hours and 37 minutes. After that is Mercury whose day equals 58 earth days, 15 hours, and 30 minutes.

In eighth place, we have Venus whose day equals 243 earth days! This is quite insane, you know why? Because Venus’s year is 224 earth days! Venus’s year is shorter than its day! And this is because Venus travels around the Sun faster than it rotates around itself.

So planets’ arrangement in order of their day length comes like this: Jupiter, Saturn, Neptune, Uranus, Earth, Mars, Mercury, and Venus.

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All in all

After we have learned about the different orders in which we can put the eight planets of our Solar System, here’s a table vision of them all.

Distance from
the Sun
(closest to furthest)
Heat
(hottest to coldest)
Size, diameter,
and mass
(smallest to biggest)
Orbital speed (fastest to slowest)Year length (shortest to longest)Day length (shortest to longest)
MercuryVenusMercuryMercuryMercuryJupiter
VenusMercuryMarsVenusVenusSaturn
EarthEarthVenusEarthEarthNeptune
MarsMarsEarthMarsMarsUranus
JupiterJupiterNeptuneJupiterJupiterEarth
SaturnSaturnUranusSaturnSaturnMars
UranusNeptuneSaturnUranusUranusMercury
NeptuneUranusJupiterNeptuneNeptuneVenus

Did you notice how many orders are the same?

Conclusion

In this article, we discussed how the Solar System formed. We learned about the different space bodies that orbit the Sun. We also studied planets in a bit of detail.

After that, we learned the astounding story of the planets’ discovery. Italian astronomer Galileo made great contributions in discovering Mercury, Venus, Mars, Jupiter, and Neptune. We also understood where each planet got its name and how those names are related to the features of the planets.

Lastly, we demonstrated five different orders to arrange the planets. These orders gave us multiple interesting information about the planets. For example, Neptune has the longest year and Venus has the longest day.

The Solar System is as mysterious as it is enchanting. Humans have always looked at the sky and wondered what those teeny-tiny sparkles were. This curiosity has inspired astronomers to work hard and explore the Solar System.

So every time you see the Moon in the night sky or use your school telescope to spot Jupiter, or go to a stargazing spot during a meteor shower in summer, remember all those great astronomers who devoted their lives to exploring the Solar System and tell us about the enchanting universe we are floating in.

Have you ever wondered what stands beyond our blue sky? Our planet Earth is part of the solar system that is home to the Sun -a star-, eight planets, more than 200 moons, countless comets and asteroids, and dwarf planets like Pluto.

Solar System
Solar System for Kids

Our system is called the ‘solar’ system because our star, the Sun, is called ‘Sol’ in Latin. The Sun is the center of our solar system, and its great gravity pulls all the planets, comets, and asteroids towards it. But rest assured, these do not ‘fall’ into the sun, they simply orbit it, thanks to gravity.

Quick fact! Our Sun is just one of the millions and millions of stars that wander within our cosmic galaxy!

The solar system itself is just a tiny part of our galaxy that is called the Milky Way galaxy. Our solar system orbits the center of our galaxy once every 225 years. Our galaxy gets its name from how it looks. If you look at the Milky Way in a very unpolluted night sky, you can see that it’s shaped like spilled milk. The name ‘Milky Way’ is taken from the Romans, who used to call it ‘via lacteal,’ which means ‘milky way/road.’

The Sun

The Sun rises every day, and it provides us with light and warmth. But how long has the Sun been doing that? Our Sun has been up in the sky for about 4.5 billion years. Pretty old, right? Scientifically speaking, this is an average age for stars. Our Sun is a relatively young star, compared to our galaxy, which is 13.5 billion years old! 

Our Sun is an enormous ball of hot helium and hydrogen. It is basically a boiling hot ball of gases. The Sun’s core, which is the hottest part of it, has a temperature of 27 million degrees Fahrenheit (about 15 million degrees Celsius)! Though the Sun is the closest star to our home, the Earth, we are not too close to it. In fact, the Sun is approximately 93 million miles away from Earth! So, it is close enough to provide us with the necessary warmth and solar energy. And this is why our Sun is so vital for us and all living creatures on Earth. 

Our Sun’s gravity holds the solar system together. It keeps the planets, dwarf planets, moons, comets, asteroids, and more in orbit around it. When the Earth completes one cycle orbiting around the Sun, it completes one year.

The Earth also rotates and spins around itself. Our Earth takes 24 hours to spin around its axis, and this is what we call a ‘day’! That is why there are times when you see the Sun in the sky, which we call daytime, and there are other times when the sky is dark and you can see the moon, which we call nighttime. The length of daytime and nighttime changes over the year. This is why, in summer, the daytime is longer, and, in winter, it is shorter. It depends on where you live. So, let’s say that you’re starting your day where you live. In another country, it would mean nighttime for them. Pretty amazing, right?!    

Like all stars, our Sun will eventually die. A star dies when it uses all its fuel, which is hydrogen. When it starts to die, the star will expand into a red star. When our Sun expands into a red giant star, it will become so big that it would swallow up Mercury and Venus, and probably Earth. It will then become a crystal white dwarf. But no worries! Our scientists say that our Sun is a little less than halfway through its lifetime and will last another 5 billion years before it becomes a white dwarf. 

The Planets

Now that we have talked about our Sun, let us explore the unique 8 planets that orbit it! 

Mercury

Planets for Kids
Planets for Kids

Did you know that Mercury is the smallest planet in our whole solar system? It is also the closest of our planets to our Sun. If you look at our Sun while you’re on Mercury, it will appear three times bigger than how it looks from our Earth! You might think that, since Mercury is the closest to our Sun, it must be the hottest. But that’s not true! The hottest planet in our solar system is Venus, and we will talk about it more in the next section. 

Because it is so close to the Sun, it takes Mercury 88 days to complete its cycle around the Sun. So, a year on Mercury would last for only 88 days. However, the day on Mercury is much longer than our Earth day. Mercury takes 59 Earth days to complete one orbit around its axis.

Because it is so close to the Sun, it takes Mercury 88 days to complete its cycle around the Sun. So, a year on Mercury would last for only 88 days. However, the day on Mercury is much longer than our Earth day. It takes Mercury 59 Earth days to rotate around its axis.

Mercury is one of the terrestrial planets. A terrestrial planet is a rocky planet that has a hard surface and a metal core. Earth, Mercury, Venus, and Mars are all considered terrestrial planets. 

Mercury doesn’t have any moons. It also doesn’t have any rings around it. And it looks so much like our own moon. It has a greyish-brown color and bright streaks on its surface called ‘crater rays.’ Crater rays are formed when comets or asteroids hit the surface of a planet or a moon.

As Mercury is the fastest planet to orbit the Sun, its name has an interesting story behind it. ‘Mercury’ was the name of one of the Roman gods. He was a messenger and known as the god of travelers. Because of his winged hat and sandals, he could fly and was the fastest among the other gods.

Venus

Venus for Kids
Venus for Kids

Venus is the second closest planet to the Sun, and it is our Earth’s neighbor. Venus is a terrestrial planet as well. Although Venus is more distant from the Sun than tiny Mercury, it is the hottest planet. Venus is hotter than Mercury because of its dense atmosphere. Venus’ atmosphere is toxic and is filled with carbon dioxide. It is also covered with yellow clouds of sulfuric acid that trap heat and make an enormous greenhouse effect. Surface temperatures on Venus are about 900 degrees Fahrenheit (475 degrees Celsius), which is enough to melt lead. Venus is also believed to have volcanoes. And this is why scientists believe that it would be most unlikely to be able to live on Venus. 

Due to the similarity in size and mass with the Earth, Venus is often called the Earth’s twin. However, in reality, they are so different from each other. One of the reasons why Venus is very different from Earth is because of its high temperature. Another difference is that Venus rotates backward. And a day on Venus would not equal a day on our Earth. A day on Venus lasts for 243 Earth days. Whereas a year on Venus would be only 225 Earth days. This means that a day on Venus is longer than a whole year on it! 

Even though it is called the Earth’s twin, Venus does not have any moons. One interesting fact about Venus is that scientists cannot determine what color it is. To the human eye, Venus appears to be white and yellow, with a reddish and brown surface. We see yellow strips because of the sulfur in Venus’ atmosphere. And because Venus rotates backward, if you are to be on it, the Sun would rise in the west and set in the east, opposite of what we see on our Earth. 

Because ancient Romans could easily see the seven brightest objects in the sky, they named the objects after their most important gods. Like Mercury, Mars, Jupiter, and Saturn, Venus is named after one of the goddesses of Roman mythology, the goddess of love and beauty, Venus.

Earth

Earth for Kids
Earth for Kids

Now, let’s talk about our home planet, the Earth!

Earth is the third planet from the Sun, the fifth largest planet in our solar system, and the only planet we know of that humans can live on. Earth is the third and biggest terrestrial planet. Earth is considered the only planet to have liquid water on its surface. Around 71% of the Earth is covered by water and only 29% by land. 97% of Earth’s water is salted water, which makes up our oceans. Only 3% of the water is freshwater that we can use to drink. This freshwater comes from rivers, lakes, and groundwater. With this much water on its surface, the Earth has earned its nickname ‘the Blue Planet.’

Earth has a more unique atmosphere than any other planet. The atmosphere consists of 78% nitrogen, 21% oxygen, and 1% other gases, such as carbon dioxide and argon. The amount of oxygen might seem so little for all of us to breathe, but it is just the right amount. Earth’s atmosphere also plays an important part to protect and shield us from the harmful radiation coming from the Sun. It also protects us from coming meteoroids. When a meteoroid burns up in our atmosphere, it is displayed as a ‘shooting star’ that we all see in the night sky. This is called a meteor. If a meteoroid survives and does not burn up, it hits the ground and is called a meteorite.

It takes Earth 24 hours to spin around its axis. We call this a ‘day.’ When Earth completes one cycle of orbiting the Sun, we finish one year. One year on Earth lasts exactly 365.25 days. 

Fun fact! The extra quarter of the day means that every four years, we add one day to our calendar. When this happens, we call this day a ‘leap day’ and the year it is added to is called a ‘leap year.’ And this is why we sometimes see on our calendar that February has 29 days instead of 28!

Since Earth is one of the terrestrial planets, we know that it has a metal core. Earth’s core is made up of mostly iron and nickel. It is so hot at the Earth’s core that these metals are all in liquid form. 

Earth is the only planet to have one single moon. Our moon is our only natural satellite. A satellite is an object that orbits a planet or a star. We have many superficial satellites, but our moon is the only one that is naturally lovely. 

Our moon is the brightest object we see in our night sky. Its light guides us in the night and makes our night sky more beautiful. However, the moon is not naturally bright. The reason our moon is so bright is that it reflects the light that is coming from the Sun.

The name ‘Earth’ is a 1,000-year-old name. Our Earth is the only planet that is not named after Greek and Roman gods and goddesses. The word ‘Earth’ comes from the Germanic word ‘erde’ and the old English word ‘ertha,’ and they both mean ‘ground.’ 

You would think that since we are living on Earth, we would know everything about it. That is not true. There are so many mysteries about our home planet that we are yet to discover! 

Mars

Now we move on to the next planet! The famous ‘Red Planet!’ Mars is called the Red Planet because of rusting (which is also called oxidation) of the iron minerals that are found in Mars’s soil, making the surface look red. Mars is probably the easiest to spot in a clear night sky –it is a bright red dot! Mars has a thin atmosphere and is one of the four terrestrial planets. This means that it is rocky. Mars is the second smallest planet. It is actually half the size of Earth.  

Planet Mars for Kids
Planet Mars for Kids

The name ‘Mars’ also has a little bit of reddish story to it. As mentioned before, the ancient Romans could easily spot the brightest objects in the sky, and Mars was one of them. Its reddish color reminded them of the blood that was shed in wars. So, they named Mars after their war god.

The day on Mars is 24.6 hours long, which is a little longer than Earth’s day. Because of its similarity with the day on Earth, Martian days are called ‘sol days,’ short for ‘solar days.’ A year on Mars lasts 669.6 sols, which equals 687 Earth days. 

Mars has a thin atmosphere made up mainly of carbon dioxide, nitrogen, and argon gases. Unlike the Earth’s sky, Mars’ sky would look reddish, and that is because of the particles of suspended dust. Mars’ atmosphere also differs from Earth’s in one more characteristic. Mars’ atmosphere does not offer protection from comets, asteroids, and meteorites. 

You might wonder about the weather on Mars. It appears that Mars is much colder than Earth. Because Mars’ atmosphere is too thin, the heat coming from the sun easily escapes this planet. The temperature on Mars can get as high as 70 degrees Fahrenheit (20 degrees Celsius). And it can drop as low as -225 degrees Fahrenheit (-153 degrees Celsius). 

The wind on Mars is not very pleasant. It can get strong enough to create dust storms that cover the whole planet. It can take months before all the dust can settle. 

One of the most interesting findings on Mars is Olympus Mons. Olympus Mons is the tallest and largest volcano/mountain in the solar system. It is three times taller than our Mt. Everest! Gigantically large, right?!

There has been evidence that Mars once had water. It is geologically known that where there is water, there would be traces left on the landscape. Flowing water carves out riverbeds, and this is exactly what a NASA rover has found when sent on a mission to explore any traces of water on Mars.

Now let’s move on to moons. Mars has two small moons named Phobos and Deimos. These moons are named after the sons of the Greek war god, Ares (Mars to the Romans). The two moons look like potatoes!

The moon Phobos is heavily cratered. This means that it is impacted by a lot of hitting comets, asteroids, and meteorites. According to NASA, Phobos is moving towards Mars slowly. It will eventually crash into Mars or break apart in about 50 million years.

Like Phobos, Deimos is a heavily cratered moon. It is about half the size of its brother, Phobos. Although you would think that Deimos would look like it has deep craters, it actually looks very smooth. This is due to the loose dirt that fills up the craters. It is unlikely that Deimos would crash into Mars, like Phobos, because it orbits farther away from the planet.

You might be wondering: “how do we know all this stuff about Mars?!” Mars is actually the most explored object in our solar system. It is the only planet that we have sent rovers to explore. NASA currently has two rovers on Mars. One is named ‘Curiosity’ and the other is named ‘Perseverance.’ Perseverance’s mission is to look for signs that could tell us if Mars had any form of life. UAE and China have also sent robotic machines to explore the alien planet. NASA believes that it might be possible to launch a man-led mission to Mars by the 2030s.

Jupiter

Planet Jupiter for Kids
Planet Jupiter for Kids

Next, we have the biggest planet in our solar system, Jupiter! Jupiter is so big that it is twice as massive as all the other planets combined. Jupiter is one of the Jovian planets, along with Saturn, Uranus, and Neptune. A Jovian planet is composed entirely of gases, mostly hydrogen and helium. Jovian planets do not have solid surfaces like terrestrial ones. But scientists think that Jupiter’s core may be solid and is about the size of the Earth. 

When the solar system was formed 4.5 billion years ago, Jupiter took most of the mass that was left from forming the Sun, making it twice as massive as all the other planets combined. Although Jupiter has the same materials found in a star (helium and hydrogen), it didn’t become a star. It was not big enough to ignite as a star.

The stripes you see on the surface of Jupiter are clouds of ammonia and water. The big red spot that we see when we look at pictures of Jupiter is a violent storm that has been going on for hundreds of years. Jupiter also has rings, like other Jovian planets, but they are too faint to see. They are like rings made of dust!

Jupiter is so big that its name has a significant meaning behind it. Because Jupiter is the biggest planet in our solar system, it was named after the king of the ancient Roman gods. In Greek, Jupiter is called ‘Zeus,’ who is the father of all Greek gods. 

Jupiter has the shortest day in our solar system. It takes Jupiter only 10 hours to spin around its axis. While it has the shortest day, Jupiter has one of the longest years in our solar system. It takes Jupiter 12 Earth years to orbit the Sun. 

One of the interesting facts is that Jupiter has the largest ocean in our solar system. However, it is not an ocean made of water. It is an ocean made of liquid hydrogen. Due to its thick atmosphere, the temperature and pressure are huge, and they turn the hydrogen gas into a liquid.

Unlike Earth and Mars, Jupiter has many moons. The moons are so many that it is often said that Jupiter forms its own solar system. Jupiter has 53 confirmed moons and 26 moons that are still awaiting confirmation. Jupiter has four large moons -they are the largest-. Each moon is unique on its own and we will explore them in the Moons section here. These four moons are named: Io, Europa, Ganymede, and Callisto. 

Spacecraft, probes, and orbiters observed the giant planet such as Pioneer 10 and 11, New Horizons, Cassini, and Juno. Juno is the latest spacecraft that landed on Jupiter to study Jupiter’s chemistry and atmosphere. So, there are still many things to know about Jupiter in the future!

Saturn

We will now begin talking about the most unique planet in our solar system! Saturn is the second-largest planet in our solar system, and it is the most unique-looking one. Saturn is not the only planet to have rings, but it has the most beautiful ones. Like its neighbor, Jupiter, Saturn is mostly made up of hydrogen and helium. 

Saturn for Kids
Saturn for Kids

Saturn is one of the brightest objects in the night sky that could be seen easily by the ancients without a telescope. It is named after the god of agriculture and wealth in Roman mythology. This Roman god is the father of Jupiter. 

Like Jupiter, a day on Saturn is pretty short. A day on Saturn lasts for only 10.7 hours. This is the time that it takes Saturn to spin around its axis. However, it takes Saturn 29.4 Earth years to orbit the Sun completely. 

Saturn has 82 moons. There are 53 confirmed moons and 29 awaiting confirmation. This makes Saturn the planet that has the most moons in our solar system. We will know about Saturn’s most famous moons in the Moon section below. 

When you look at Saturn’s pictures, the first thing you notice is the rings around it. They are lovely and unique, and more complex than they look. The rings around Saturn are made of billions of ice and rocks that are coated with dust. Scientists think that these small objects are pieces of comets, asteroids, and shattered moons that got torn apart by Saturn’s powerful gravity. The most interesting thing about them is the different speeds that each ring orbits Saturn at. 

Uranus

Uranus for Kids
Uranus for Kids

We have nearly arrived at the end of our planet journey. This planet is the coldest one in our solar system. Uranus is one of the two ice giants in our solar system (the other one is Neptune). That is because Uranus is made of a hot dense fluid of icy materials, such as water, ammonia, and methane. All of these materials are above a small hot core that heats up to 9,000 degrees Fahrenheit (4,982 degrees Celsius). Uranus does not have a solid surface. Uranus’ atmosphere is made of hydrogen, helium, and methane. The methane in Uranus’ atmosphere absorbs the red portion of the light that is coming from the Sun and reflects it as blue. And this is how Uranus gets its beautiful blue color. Uranus also has a set of 13 rings that are faint in color. The outer rings are the only ones that are bright and can be seen vividly. 

Scientists think that when our solar system started to form, Uranus and Neptune were much closer to the Sun. But 4 billion years ago, they both were moved to the outer part of the solar system. 

It was not possible for people in ancient times to see Uranus with the human eye. So, Uranus was named after they developed telescopes. Like the rest of the planets, scientists decided to use Greek and Roman gods’ names as well. In Greek mythology, Uranus was the sky god, father of Saturn, and grandfather of Jupiter. 

One day on Uranus has about 17 hours, and this is how many hours it takes Uranus to rotate. It takes Uranus 84 Earth years to make a complete orbit around the sun. Uranus is also one of the two planets that rotate backward (the other planet is Venus). This means that the Sun rises in the west and sets in the east. 

The weather on Uranus is very extreme. This ice giant has the coldest temperature ever recorded in our solar system, which is -371.56 degrees Fahrenheit (-224.2 degrees Celsius). Uranus is not the coldest planet because it is way farther away from the Sun. Uranus is the coldest because it rotates on its side. Billions of years ago, a giant object crashed into Uranus causing it to turn on its side.

Quick fact! Did you know that Uranus is the only planet that rotates on its side?

Another interesting thing about Uranus is its moons. We know that most of the natural satellites of other planets take their names from Greek and Roman mythology, right? Uranus’ moons are different. There are 27 moons in total orbiting Uranus, and they all have unique names. Each moon is named after a character from the literary works of Shakespeare and Alexander Pope.

Neptune

Neptune for Kids
Neptune for Kids

We have finally reached the last planet! Neptune is the most distant planet from the Sun. It is dark, cold, and has the most violent winds. It is an ice giant, just like its neighbor Uranus. It is mostly made of a hot dense fluid of water, methane, and ammonia. All of these materials exist above a small hot core. Like Uranus, Neptune does not have a solid surface. Its atmosphere is so big that it merges with water and icy materials. Neptune’s atmosphere is mostly made of hydrogen, helium, and methane. Again, like Uranus, the methane in Neptune’s atmosphere absorbs the red portion of the light that is coming from the Sun and reflects it as blue. 

When you look at space photos taken of Neptune, its blue color reminds you of the blueness of the sea, right? Its beautiful blue color is the reason behind its unique name. Neptune was the sea god in Roman mythology. Because of the similarity between Neptune’s color and the blue color of the sea, scientists picked ‘Neptune.’ And it is truly the perfect name for it!

The time it takes Neptune to rotate once is 16 hours. That means that a day on Neptune lasts only 16 hours. However, a year on Neptune is so long. Neptune makes a complete orbit around the Sun every 165 Earth years. That’s a lot of time to wait for your birthday! 

Fun fact! In 2011, Neptune completed its first orbit around the Sun -165 Earth years- since the planet was discovered in 1846. 

Neptune has 14 moons. They are all named after minor Greek gods and nymphs. One of these moons is called Triton and it is the largest moon that orbits Neptune. We will know more about the moon Triton in our Moon section below.

Moons

The next objects we are moving on to are moons! Although Mercury and Venus do not have moons, we are going to explore other planets’ moons, starting from Earth to Neptune. 

But first, let’s talk about how moons were formed. A moon, also called a natural satellite, orbits planets in our solar system. Some moons are big, and some are so small. Moons are mostly formed from the gas and dust that were around the planets when the solar system was beginning to be formed. However, it is believed that some of these moons are ‘captured’ objects that were formed elsewhere and fell to orbit the planets. 

Earth’s Moon

First on the list is our lovely Moon! The Moon is the only place beyond Earth that humans set foot on. In fact, there are 12 humans who have visited the Moon. It is so easy to spot in the night sky! It illuminates our nights and makes a great companion for us in the night. 

Our Moon is our only natural satellite. It is the fifth-biggest moon in our solar system. Scientists believe that the Moon was formed after Earth and Mars crashed into one another millions of years ago. This resulted in the tearing of a piece of Earth’s molten rock. This molten rock cooled down until it formed the Moon that we see in our night sky.

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Phases of the Moon

The Moon takes 27.3 days to make an orbit around Earth while also completing one orbit around its axis. Because of this, we only see the same side of the Moon. You might think that the Moon has its natural light because it appears so bright in our night sky. However, this is not true. The Sun reflects its sunlight upon the surface of our Moon, making it bright and dazzling. People have mistakenly called the other side of the Moon that we can’t see ‘the dark side.’ This is not true. The sunlight is reflected on every side of the Moon, but we only see the same side because the Moon orbits its axis at the same time it orbits the Earth. 

On some days, we see the Moon shrinking and on other days we see it getting bigger until it reaches the full bright moon that we see. The Moon is actually the same size as always, we just view it differently. Depending on how much sunlight the Moon gets, it goes through phases. When we cannot see the Moon, it means that it is in its New Moon phase. If people in the countries of the Northern Hemisphere see a thin crescent of light on the right side of the Moon, it means that it is in its Waxing Crescent phase. When we see a half-moon, it means that it is the First Quarter phase. When we see that the Moon is between a half-moon and a full moon, this is called the Waxing Gibbous phase. Waxing means that the Moon is getting bigger (that is what appears to us). When we can see the Moon fully bright in our night sky, we call it the Full Moon phase. When the Moon is in its Waning Gibbous phase, we see that it is between a half-moon and a full moon. Waning means that the Moon is getting smaller in our eyes. In the Third Quarter phase, we see a half-moon, but it is the opposite half as compared to the half shown in the First Quarter phase. When people in the countries of the Northern Hemisphere see a thin crescent of light on the left side of the Moon, it means that it is the Waning Crescent phase. 

Our Moon is responsible for tides! Tides are the change in the water level in the oceans. Because of gravity, the Moon and the Sun pull on Earth. And this causes tides. The Moon has got the bigger responsibility because it is closer to our Earth. 

Mars’ Moons

Mars has two small moons called Phobos and Deimos. They look like asteroids and many people think that they were once in the asteroid belt and were pulled by Mars’ great gravity. 

Phobos orbits so close to Mars that it orbits the Red Planet three times a day! Scientists believe that Phobos will eventually crash into Mars when it dies.

When we look at pictures of Phobos, it really looks like a potato. It has many craters and that is because of the many hitting asteroids, comets, and meteorites. 

Deimos looks like another potato! But its surface appears much smoother than that of Phobos because of the dust that is filling its craters. It is smaller than Phobos and orbits farther away from Mars. 

Jupiter’s Moons

Jupiter is one of two planets (the other one is Saturn) that have the most moons in our solar system. Jupiter has 79 moons in total. It has 53 named moons and 26 awaiting their names. We will be talking about the four largest moons that orbit Jupiter, the Galilean Moons. They are called the Galilean Moons after the Italian astronomer Galileo Galilei, who first observed them in 1610. These moons are bigger than our Moon and are named Io, Europa, Ganymede, and Callisto. 

Io is known to be the only object that has many active volcanoes in the solar system. Io is one of the most colorful celestial bodies in our solar system. This is due to the sulfur and sulfur compounds on its surface. It has no water on it, unlike the other Galilean moons. Io is named after a maiden who was loved by the Greek god Zeus and was turned into a cow during a dispute between Zeus and his jealous wife Hera. 

The next moon on the list is called Europa. Europa is one of the most interesting worlds to explore because scientists found suitable environments for some form of life on it. From observations, scientists found that Europa’s surface looks like a sea of crushed ice. Scientists believe that beneath this layer there might exist an ocean that may contain twice as much water as all of our oceans combined. Europa was named after a princess who was abducted by Zeus (Jupiter, in Roman mythology) to be his lover. 

Our next moon is called Ganymede. It is the biggest moon in our solar system. Exploring Ganymede is important to scientists because NASA’s Hubble Telescope found evidence of an underground saltwater ocean on it. Scientists think that this ocean will have more water than the water on Earth’s surface. Not only this, but scientists have found that Ganymede’s thin atmosphere contains small amounts of oxygen. This moon is named after a young boy who was carried to Olympus by Zeus and made the cupbearer of all the gods.

Our last big moon is Callisto. Callisto is Jupiter’s second-biggest moon and the third biggest one in our solar system. It was once thought ‘dead.’ However, in the 1990s, it was discovered that it may have a salty ocean beneath its surface. This made Callisto on the list of the worlds that may have some sort of life on it. Callisto is named after a woman who was Zeus’ lover. When Hera found out about their relationship, she turned Callisto into a bear.

Saturn’s Moons

Now, we are going to explore the moons of our beautiful Saturn. Saturn has 82 moons, making it the possessor of the largest number of moons in our solar system. We will explore two of Saturn’s most famous moons!

The first moon is called Titan. It is the second-largest moon in our solar system. It is the only moon in our solar system that has clouds and an atmosphere like our planets. Its atmosphere is made mostly of nitrogen, like our atmosphere. Titan’s surface is made of water ice as hard as a rock. However, scientists believe that beneath its surface there is an ocean of liquid water. Titan takes its name from Greek mythology. A titan was a member of a family of giants that used to rule the world before the Olympian gods.

The next moon is called Enceladus. Enceladus has the whitest and loveliest surface in our solar system. Wouldn’t it be incredible if we could live on such a beautiful planet? In fact, scientists think so! Enceladus makes it easy for us to examine it. It has an icy ocean, and it sprays icy particles in space. One of our spacecraft has got samples from these particles and examined them. Scientists found out that Enceladus has most of the chemical ingredients that are needed for life.

Uranus’ Moons

Uranus has so many moons! It has the biggest number of moons in our solar system. All of the discovered moons are named after characters from the works of the playwright Shakespeare and the poet Alexander Pope. Uranus has five large moons, and they are Titania, Oberon, Ariel, Umbriel, and Miranda. Titania is the largest of them and Miranda is the smallest. These moons are made of rock and water ice. Many small moons exist between these large moons, and they are almost like asteroids! But thankfully, they do not crash into one another. 

Neptune’s Moons

Neptune has 14 moons but the most distinguished one is Triton. Triton is the largest of Neptune’s moons. Scientists think that Triton was formed in the Kuiper Belt but was pulled by Neptune’s gravity. Triton is special because it is the only moon in our solar system that orbits in the opposite direction of its planet rotation. This is called a retrograde orbit. Triton is named after Poseidon’s son (Poseidon is Neptune in Greek mythology).

Dwarf Planets

Our next stop is all about dwarf planets! Dwarf planets are too small to be considered planets, but they are not that small to be considered any other small celestial body, like asteroids for example. Another reason why they are not considered planets is because their orbit has other small objects. A planet’s gravity can push these small objects out of its orbit. However, dwarf planets do not have a powerful gravity.

We are sure you’ve heard about the dwarf planet Pluto, but they are other dwarf planets that we are going to explore here!

Pluto

Pluto is the most well-known of the dwarf planets. This is because it used to be the ninth planet in our solar system! But when scientists found out more about Pluto and other objects as small as it, they removed poor Pluto from the list of planets. But worry not! Even though it is not a planet, Pluto is a fascinating world for us to explore. It is smaller than our moon and it has a cute spot that looks like the heart of its surface!

One day on Pluto is about 153 hours long, that’s too long for a day! And a year on Pluto lasts 248 Earth years. A long time to wait for your birthday, right? 

Pluto exists inside the Kuiper Belt. Although Pluto is very far away from the Sun and was considered the ninth planet, it sometimes was closer to the Sun than Neptune. Pluto also has its own moons. It has five moons and its largest one is called Charon.

Fun fact! Pluto was named by an eleven-year-old English girl! She picked its name from Roman mythology. Pluto was the name of the underworld god.

Ceres

The next dwarf plane that we are going to visit is Ceres. Ceres exists in the asteroid belt. The asteroid belt is a place between Mars and Jupiter that has most of the asteroids in our solar system. Ceres was once considered an asteroid, but scientists thought that it was way too big to be considered one. However, it is considered the smallest of the dwarf planets. Another difference between Ceres and asteroids is that it does not look like a potato! Ceres actually has a round body.

A year on Ceres is only 4.6 Earth years long. But Ceres has one of the shortest days in our solar system. It takes Ceres only 9 hours to spin around its axis. Unlike other dwarf planets, Ceres does not have any moons. 

Ceres is one of the objects that scientists want to explore for any potential of life. In one of the missions, it was spotted that Ceres has water vapor. This means that it has water! And we know how water is important for life. That is why scientists plan to send missions to Ceres in the future.

Fun fact! Ceres is named after the corn and harvest goddess in Roman mythology. The word ‘cereal’ also comes from the same name.

Makemake

Our next stop is a bright dwarf planet, Makemake. Makemake is the second brightest dwarf planet, after Pluto, that could be observed by a telescope. Makemake is a very important object in space history. It was one of the objects, along with Eris, that were discovered that made Pluto get kicked out from being the ninth planet. Its discovery made scientists create a whole category just for these objects that were smaller than the rest of the planets. Makemake is inside the Kuiper Belt. Makemake has no atmosphere. However, when it is the closest to the Sun, it develops a thin atmosphere. A day on Makemake is 22.5 hours long, which is slightly shorter than a day on Earth. However, it takes Makemake 305 Earth years to orbit the Sun. Makemake is named after the fertility god in Rapa Nui mythology. 

Huamea

Our next dwarf planet is a fast one! Haumea is in the Kuiper Belt. Haumea is the same size as Pluto, but it has a weirdly oval shape. Haumea is one of the fastest rotating objects in our solar system. It only takes Haumea 4 hours to spin around its axis. However, a year on Haumea is 285 Earth years long. Haumea is the second dwarf planet to have more than one moon, after Pluto. It has two moons named Namaka and Hi’iaka. Haumea is named after the Hawaiian goddess of fertility. 

Quick fact! No spacecraft has ever visited Haumea or traveled past it. Everything we know about this dwarf planet is from observations with telescopes. 

Eris

We have finally arrived at our last dwarf planet, Eris. Eris is about the size of Pluto that it is nicknamed ‘Pluto’s almost perfect twin.’ Eris is also a very important object because it made scientists reconsider Pluto as a planet. It takes Eris 557 Earth years to orbit the sun, but the length of its day is similar to ours. Eris takes only 25.9 hours to spin around its axis. Eris is named after the goddess of chaos in Greek mythology. Eris has only one moon called Dysnomia. This moon is actually named after goddess Eris’ daughter. 

Asteroids

The next objects that we are going to explore are asteroids! If you look at any space pictures of asteroids they would look like ill-shaped rocks, like potatoes. They are made of rock and sometimes, metal. When our solar system was formed 4.5 billion years ago, there were some leftovers. Asteroids are the remnants of this formation. The current known asteroid count is 1,113,527. It is believed that the total mass of all these asteroids combined is lesser than that of our moon. Asteroids come in all sizes. Some are just a few feet in diameter. Some are hundreds of miles in diameter. 

There are three types of asteroids that we are going to explore. 

  • Carbon asteroids: they are made up mostly of carbon and they are very dark in color. Around 75% of asteroids are carbon ones.
  • Stony asteroids: they are made up mostly of rock and some amounts of metal.
  • Metallic asteroids: they are made up of metals, primarily iron and nickel, and some amounts of stone.  

Most asteroids exist and orbit the Sun in a ring called the Asteroid Belt. This belt exists between Mars and Jupiter. Scientists believe that there are millions and millions of asteroids in the asteroid belt.

There are some big asteroids out there. They are bigger than other asteroids to the point that they are considered minor planets. The four biggest asteroids are named Ceres, Vesta, Pallas, and Hygiea in order. They are, like our planets, named after Greek and Roman goddesses.

Ceres is the biggest asteroid that we know of. It is so big that it is categorized as one of the dwarf planets. Vesta is the second biggest asteroid and is the brightest asteroid when looked at from Earth. Pallas was the second asteroid to be discovered after Ceres. It is considered the largest object in our solar system that is not round. Hygiea is the biggest carbon asteroid that we know of. 

Explorers have found that there are other asteroids outside the asteroid belt. There are two groups: the Trojan asteroids and Near-Earth asteroids. Trojan asteroids are the ones that share an orbit with a planet or moon. However, they do not crash into the planet. Most of the Trojan asteroids orbit the Sun with Jupiter. Most Near-Earth asteroids explode when they enter the Earth’s atmosphere.

Quick fact! Some scientists believe that millions of years ago when dinosaurs existed, a large asteroid hit the Earth and caused them to become extinct. 

Comets

Our next fascinating objects are called comets! Comets orbit the Sun, just like our planets do. They are made of dust and ice that were left from the formation of our solar system billions of years ago. Comets are best known for their spectacular tails. 

Comets come from two distant places that exist in our solar system. The first place is called the Kuiper Belt. This place exists beyond the orbit of Neptune. The comets that come from the Kuiper Belt are called short-period comets because they orbit the Sun in a short period. They take about 200 years to travel around the Sun.

Other comets come from a far more distant place that is called the Oort Cloud. The comets that come from the Oort Cloud are called long-period comets. They are called that because they take more than 250,000 years to complete an orbit around the Sun.

A comet has a frozen part that is called a nucleus. A nucleus is made up of ice and frozen gases. When a comet is near the Sun, its nucleus heats up. This causes ice to turn into gas and the gas and dust form a cloud around the comet. This cloud is called a ‘coma.’ The gas and dust move away from the nucleus and sunlight pressures them until they form a bright tail behind the comet. When scientists took a closer look, they found that this tail is made up of two separate tails. The first tail is made of dust, and the second is made of ions. These ions are gas molecules that are charged with electricity.

Meteoroids, Meteors, and Meteorites

Next on our list are Meteoroids, Meteors, or Meteorites. Actually, these terms are very different from each other. A meteoroid is a space rock. It is called that only when it is in space. Meteoroids vary in size, from dust grains to small parts of asteroids, comets, and even moons. Some meteoroids are made of rock, some are metallic, and some are made from both rock and metal. 

When a meteoroid enters Earth’s atmosphere at high speed, it burns up. We call this a meteor. It is also called a ‘shooting star.’ If you see a shooting star, make sure to make a wish! When a meteoroid does not burn up and it hits the ground, we call it a meteorite. 

Sometimes, we see a group of meteors. This is called a meteor shower. Meteor showers are named after the constellation where the meteors are coming from. A constellation is a group of stars that form a certain pattern. There are known meteor showers that happen at specific times of the year. For example, the Lyrids meteor shower happens in April and the Perseids meteor shower happens in August. Keep in mind that if the moon is full on any day of these months, a meteor shower will not appear.

Kuiper Belt

You might wonder about what is there beyond Neptune. Just outside Neptune’s orbit, there is a belt of icy objects that is called the Kuiper Belt. It is home to the most famous dwarf planet, Pluto. Three dwarf planets, besides Pluto, exist in the Kuiper Belt as well. It is named after the scientist Gerard Kuiper who was thinking about comets and where they come from. It was hard to see past Neptune with our best telescopes, so no one believed. It was years later when Kuiper was proved right. In 2019, a spacecraft that was traveling the Kuiper Belt spotted a snowman-shaped object. Scientists called it Arrokoth, meaning ‘sky’ in the Powhatan/Algonquian language. Arrokoth is by far the most distant studied object. 

Oort Cloud

A question may pop in your head, “what is there even past the Kuiper Belt?” The answer would be the Oort Cloud. The Oort Cloud is a place that has many icy objects. It is where long-period comets come from. There has been little known about the Oort Cloud. No object has been even observed in the Oort Cloud itself. 

There is still so much we don’t know about our universe. Every day passes, there is something to be discovered. So, make sure you witness these discoveries! 

What is the coldest planet in the solar system? You may be confused between Uranus and Neptune, the most distant planets. Technically speaking, Neptune is the coldest planet in the solar system, but Uranus does reach the coldest temperatures of any other planet.

Introduction to Neptune

Neptune is one of the eight planets that orbit the Sun in our Solar System. It is the eighth, the last and the farthest planet from the Sun. The average distance between the Sun and Neptune is about 4.5 billion kilometres. Therefore, it is the coldest planet in the solar system. Neptune is one of the outer planets and the gas giants. It is the smallest planet among the gas giants, and it is the fourth largest planet in the Solar System. It shares so much in common with Uranus, so they both are called ice giants. Neptune is a dark, cold and stormy world. Let’s discover it in depth!

Uranus and Neptune

Surface and Structure

Neptune is one of the gas giant planets. This means that it is made up mostly of gases, and it does not have a solid surface. The main two gases that make up Neptune are hydrogen and helium. Around 80% of Neptune’s mass consists of dense, hot fluid of icy materials such as water, ammonia, and methane. Inside Neptune, there are two layers: the core and a mantle.

The core is small, and it is made up of rock. The mantle is hot and liquid, and it is made of water, ammonia, and methane. Scientists think that there might be a very hot ocean under the cold clouds of Neptune, and it does not boil away because the high pressure locks it inside. 

Atmosphere and Temperature

Neptune has a thick atmosphere that is made of hydrogen, helium, and methane. The atmosphere of Neptune is very windy. Sometimes dark spots form in the atmosphere, which are actually huge storms. Neptune has the wildest and strangest weather out of all the planets in the Solar System. Some winds have been able to reach up to 2,160 km per hour. These winds are 5 times stronger than the strongest winds on Earth. The average temperature on Neptune’s surface is around -353 °F (-214 °C).

Galileo Galilei LearningMole

Size

Neptune’s diameter is about 50,000 kilometres. This is about four times larger than Earth’s diameter. Neptune is nearly as big as its neighbour, Uranus. The diameter of Saturn is 2.3 times the diameter of Neptune. The largest planet in the Solar System, Jupiter, has 2.8 times Neptune’s diameter. Neptune is nearly four times larger than Earth and Venus. It has 7.2 times the diameter of Mars, and more than 10 times the diameter of Mercury, the smallest planet in the Solar System.

planets in the solar system

Orbit and Rotation

Like all planets, Neptune has two types of motion: orbit around the Sun, and spin about its centre. Neptune’s journey around the Sun takes so much time because it is so far away from the Sun. It takes Neptune about 165 Earth years to complete only one orbit around the Sun. So, a year on Neptune is about 165 Earth years.

On the other hand, Neptune spins about its centre quickly. In fact, it has the third shortest day of any planet in the solar system. A day on Neptune is actually shorter than a day on Earth. Neptune completes one rotation, or spin, in about 16 hours. So, a day on Neptune is equal to about 16 hours.

Moons

There are 14 moons around Neptune. The largest moon is Triton. It is nearly the same size as Earth’s moon, and it is bigger than the dwarf planet Pluto. It is shaped like a sphere, and it has a rotation that is opposite that of Neptune. Scientists believe that Triton was actually a dwarf planet, but the gravity of Neptune had pulled it into its orbit. Triton is the seventh largest moon in the Solar System.

Rings

Like the other three gas giants, Neptune has a ring system. There are six narrow rings that surround Neptune, but they are faint. They are not as large as the rings of Saturn. The rings are mostly made up of dust.

Neptune

Name

Planet Neptune is named after the Roman god of the sea. In Greek mythology, he was known as Poseidon. Neptune was given the name of the Roman god of the sea because of its blue colour. In addition, all of Neptune’s moons have been named after water deities.

Discovery and Exploration

Although Neptune is a huge planet, it is so far away that people on Earth cannot see it without a telescope. So, it remained undiscovered for centuries. In 1846, Urbain Le Verrier, John Couch Adams, and Johann Galle discovered Neptune by mathematical predictions. Astronomers were calculating the orbit of Uranus and observed that the planet was not matching their calculations. So, they suggested that there is another planet behind Uranus that causes the disruption.

Astronomer Le Verrier predicted the place of that planet, and Johann Galle found it one degree away from that predicted point. So, Neptune became the first planet to be discovered by mathematical calculations and predictions.

In 1989, NASA’s Voyager 2 spacecraft flew by Neptune and studied it closely. This was over 140 years after Le Verrier’s predictions about Neptune. Voyager 2 is the first and the only spacecraft to visit Neptune. It provided us with much information about the planet and its moons. It also confirmed that Neptune had faint rings like other gas giant planets. 

10 Interesting Facts about Neptune

  1. Both Neptune and Uranus share similar compositions, and they differ from the other gas giants: Jupiter and Saturn. Because of this, Neptune and Uranus are classified as ice giants rather than gas giants. 
  2. Neptune is very similar to Uranus in terms of size, mass, composition and rotation. So, they are referred to as twin planets.
  3. Neptune is the only planet that is not visible to the naked eye from Earth. You can see it only with instruments such as telescopes. 
  4. Neptune is the last and most distant planet from the Sun, so it has only one neighbour, which is Uranus.
  5. Although Neptune is the farthest planet from the Sun, Uranus sometimes reaches temperatures that are colder than Neptune’s temperatures.
  6. In 1613, Galileo Galilei observed Neptune, but he thought that he observed a star and failed to find it again.
  7. Even though Neptune is a gas giant, it has the second largest gravity of all other planets in the solar system after Jupiter. 
  8. If you weigh 100 pounds (45 kilograms) on Earth, you would weigh 114 pounds (52 kilograms) on Neptune.
  9. The space journey from Earth to Neptune takes about 12 years.
  10. Neptune’s moon Triton is the coldest known object in our solar system. Its surface temperature can dip down to -235° C. It has an extremely thin atmosphere. 

You can learn more and see pictures on NASA’s website. Click here!

Planets are large objects, they are shaped like a slightly squashed ball called a spheroid. Planets are smaller than stars, and they are pale. Let’s learn together what is the solar system and what are the eight planets in the Solar System???

What is the Solar System?

The Solar System formed billion years ago. It consists of the Sun and everything that orbits or travels around the Sun. The Sun is a star that gives us light and heat and is made up of hot gas. The Solar System consists of the Earth, the remaining planets, stars, asteroids, and comets that come out to revolve.

Not all thing in the Solar System orbits the Sun. For example, the Moon revolves around the Earth. Do you know that most of the solar system is empty space although it has a lot of things? The solar system is a small part of a big system of stars and other objects called the Milky Way galaxy. 

The Milky Way

There are three types of planets in the Solar System:

Terrestrial or rocky are almost made up of rocks.

Jovian or gas giants are almost made of gas.

Icy planets are almost made of ice.

There are “8” planets that orbit around the Sun. Here are the planets from the closest to the farthest: 

Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune.

Mercury

Planets for Kids
Planets for Kids

Mercury is considered the smallest planet, and closest planet of all to the sun. Its orbit around the sun takes about 87 Earth days. It has a radius of 2,439.7 km. Mercury is made of metallic and silicate material. Mercury is considered a terrestrial planet.

Mercury is a terrestrial planet, its surface looks like the moon. It has many craters because it does not have an atmosphere to slow objects down. Most of Mercury’s surface is greyish-brown.

Many satellites have been sent to Mercury to discover it. The first satellite was NASA’s MARINER10. It took many pictures of Mercury’s surface. Mariner 10 found that Mercury has many craters and got a lot of information about Mercury’s magnetic field. Mercury’s magnetic field is similar to the Earth’s magnetic field.

The second satellite to discover Mercury was NASA’s MESSENGER. It made a chart of most of Mercury. MESSENGER  studied Mercury’s high density, magnetic field, the structure of its core, ice at its poles, and thin atmosphere. 

But unfortunately, MESSENGER crashed into Mercury’s surface.

Venus

Venus is the second planet from the sun. Its day is longer than a year. Venus’s year length is 225 Earth days. Venus orbits around the Sun about 108 million km. It completes an orbit every 224 days. It has a radius of 6,051 km. 

Venus for Kids
Venus for Kids

Venus is considered a terrestrial planet like Mercury. It has a lot of volcanoes, its surface appears as if it has been shaped by volcanic activity. Venus’s atmosphere is a combination of carbon dioxide and nitrogen gas with clouds of sulphuric acid. The pressure on Venus is too high. 

Venus has been discovered by many satellites. One of them was Mariner 2. It discovered the atmosphere of Venus, its magnetic field, and its mass. It is still orbiting around the Sun today. The other one was Venera 15. It was made to study the surface of Venus.

Earth 

Earth for Kids
Earth for Kids

Earth is the third planet from the sun. it goes around the Sun once. It has a radius of 6,37 Km. It has a large amount of water on its surface, and because of its water Earth becomes our home. Our Earth planet is unique for many reasons. Water covers roughly 71% of Earth’s surface.

A fifth of Earth’s atmosphere consists of oxygen, produced by plants. Earth is considered the only planet that supports life because of oxygen. This oxygen also forms the ozone layer which protects Earth’s surface from bad ultraviolet radiation from the Sun.

Earth is also a terrestrial planet, so Earth is rocky. It is considered the largest of the rocky planets. Earth isn’t too hot and isn’t too cold, and this is often called the “Goldilocks distance.” Tides on Earth are created by our moon, which in turn has helped our life to improve. 

Earth also has a magnetic field, which plays a big part in preserving our planet from the effects of solar wind. Earth has no rings and has only one moon.

Mars

Mars is one of the terrestrial planets. It is considered the fourth planet from the Sun and the second-smallest planet.  Due to the rusting process of the surface minerals, you can find the surface of Mars reddish-brown in colour.

Planet Mars for Kids
Planet Mars for Kids

Mars has the largest volcano in the solar system, which is called Olympus Mons. and Mars also has one of the largest canyons in the Solar System, which is called Valles Mariners.

The most explored planet was Mars. There were about 40 discovery attempts at Mars. You can compare the days and seasons to those of Earth that’s because of the rotational period “axis tilt”.

Jupiter

Planet Jupiter for Kids
Planet Jupiter for Kids

Jupiter is considered the fifth planet from the sun and the largest planet of all. It is made up of a mixture of hydrogen and helium, which is very similar to our sun. 

Jupiter takes about 4,3 Earth days to complete one orbit around the sun. It has a radius of 69,9 km. It is a gas giant planet, made up of gases and liquids that always revolve around it. Jupiter also has a magnetic field, which is fourteen times stronger than Earth’s.

For many years Jupiter has been studied. Astronauts have sent many spacecraft, probes, and orbiters to collect data and take detailed images of Jupiter. Galileo Galilei was considered the first astronaut whose observation was detailed. His spacecraft orbited the gas giant and sent a probe into the atmosphere.

Saturn

Saturn for Kids
Saturn for Kids

Saturn is considered the sixth planet from the sun and the second-largest planet in our solar system. It takes about 29.4 Earth years to complete the orbit. Saturn has a radius of 58,2 km.

Saturn is a gas giant planet like Jupiter, which is made up of mostly hydrogen and helium. Saturn is known as “great white spots”. Every full Saturn orbit, these are some short-lived storms that seem to appear once. Jupiter’s magnetic field is bigger than Saturn’s. While Earth’s magnetic field is a little stronger than Saturn.

Saturn’s colour is pale yellow because of a high quantity of ammonia crystals, which are found in the upper atmosphere.

Saturn is considered the sixth planet from the sun. It is also the second-largest planet in our solar system. It takes about 29.4 Earth years to complete the orbit. Saturn has a radius of 58,2 km.

 Saturn is a gas giant planet, which is made up of hydrogen and helium. Saturn is known as “great white spots”. Every full Saturn orbit, these are some short-lived storms that seem to appear once. Jupiter’s magnetic field is bigger than Saturn’s. While Earth’s magnetic field is a little stronger than Saturn.

Saturn’s colour is pale yellow because of a high quantity of ammonia crystals, which are found in the upper atmosphere.

Uranus

Uranus for Kids
Uranus for Kids

Uranus is the seventh planet from the Sun and the third-largest diameter in our solar system. The day on Uranus equals about 17 Earth hours which means Uranus takes that time to complete one rotation.

Do you know what is the Uranian year?

That means the rotation of Uranus around the sun. It takes about 84 Earth years for Uranus to complete its orbit around the sun.

Uranus is also a gas giant made up of mostly swirling fluids because of that Uranus doesn’t have a real surface. Uranus appears in blue-green because of the presence of methane in its atmosphere. Uranus atmosphere mostly consists of hydrogen and helium. It has a radius of 25,36 km.

Neptune

Neptune for Kids
Neptune for Kids

Here is the eighth planet and farthest Solar planet from the Sun. Neptune is considered the fourth-largest planet in the Solar System, however, it is the smallest of the gas giants.

Neptune can rotate only one time in 16 hours and takes about 165 Earth years to orbit the sun. It has a radius of 24.7 km.

Neptune’s magnetic field is 27 times stronger than Earth’s. It is the only planet, which is so hard to see by the naked eye.

Pluto

Today, Pluto is considered a dwarf planet because of its size. In the past, scientists considered Pluto as a ninth planet but now no. It doesn’t seem to have a magnetic field. Pluto has mountains, valleys, and craters.

The Moon is the only natural satellite that orbits our planet, Earth. A natural satellite is a space body that orbits a planet. The average distance between the Moon and Earth is about 238,900 miles (384,400 kilometres). This distance is short in comparison to the distance between other planets and Earth. What most people don’t expect is that the Moon orbits Earth every 27.3 days, isn’t that strange? Are you interested in learning more about this beautiful object that lights up your sky at night? Then, let’s explore it together!

Surface and Structure

The Moon is a rocky and dusty place. It is made mostly of rock. The Moon’s surface is covered with dead volcanoes, lava flows, and many craters. The lava erupted from volcanoes billions of years ago. The craters form when meteorites crash into the Moon. The meteorites crashing into the Moon have also caused the surface to be covered with rocks and dust. Meteorites and rocks from outer space fall and crash right into the Moon because it has no atmosphere to protect it. 

Size

Our Moon is the fifth largest of all the moons in the Solar System. It is about a quarter the size of the Earth. Its diameter is about 2,200 miles (3,500 kilometres). We see it so small because it is far away from us. 

Earth and the Moon
The Moon size compared to Earth

Temperature

The Moon is not protected from heat or cold because it does not have an atmosphere. So, temperatures on the Moon vary from super hot to super cold. During the daytime, surface temperatures can reach 225 °F (107 °C). However, when the Sun goes down at night, temperatures drop to about −243 °F (−153 °C).

Orbit and Rotation

The Moon has two types of motion: orbit around Earth, and spin, or rotation, around its centre. The Moon completes an orbit around Earth in about 27 days, and it completes a rotation, or spin, about its centre in about 27 days, too. For this reason, the same side of the Moon is always facing Earth.

Phases of the Moon

You must have noticed that the Moon appears in a different shape each night, but did you know why? Here is the answer!

The Moon does not give off light itself. Instead, it only reflects light from the Sun. So, as the Moon orbits Earth, the Sun lights up different parts of its surface. This makes the Moon seem as if it is changing shape each night. Actually, it is just our view of the Moon that is changing, not the Moon itself.

The changes in the shape of the Moon are called “phases”. The moon goes through 8 major phases during 29.5 days. This is equal to one month. The Moon takes a month to go through its eight different phases because the Earth is moving around the sun at the same time. 

The eight phases of the Moon are:

1. New Moon

During this phase, the Moon cannot be seen because it faces Earth from its unlit half. This phase occurs when the Moon is directly between the Earth and the Sun.

2. Waxing Crescent Moon

During this phase, the Moon looks like a crescent. The size of the crescent increases from one day to the next.

3. The First Quarter Moon (Half Moon)

During this phase, half of the lit portion of the Moon is visible. This phase comes a week after the New Moon.

4. Waxing Gibbous Moon

During this phase, we can see more than half of the lit portion of the Moon. The size of the Moon increases from one day to the next.

5. Full Moon

During this phase, we can see the entire lit portion of the Moon. The full Moon phase occurs when the Moon is on the opposite side of the Earth from the Sun.

6. Waning Gibbous Moon

During this phase, we can see more than half of the lit portion of the Moon. The size of the Moon decreases from one day to the next.

7. The Last Quarter Moon (Half Moon)

During this phase, half of the lit portion of the Moon is visible. 

8. Waning Crescent Moon

During this phase, the Moon looks like a crescent. The size of the crescent decreases from one day to the next.

Phases of the Moon
Phases of the Moon

Moonrise and Moonset

The moon rises and sets at specific times, according to what phase it is in:

  • The New Moon rises and sets at nearly the same time as the sun.
  • The First Quarter Moon rises at mid-morning and sets at midnight. So, it is at its height around dusk, not in the middle of the night.
  • The Full Moon rises at sunset and sets at sunrise, and it is the only moon that will be overhead in the middle of the night.
  • The Last Quarter Moon rises at midnight and sets at mid-morning. 

Eclipse

Sometimes the positions of the Moon, the Sun, and Earth cause an event called an eclipse. An eclipse can happen to either the Sun or the Moon. The eclipse of the Sun is called a solar eclipse, and it occurs when the Moon blocks the view of the Sun for a short time. The eclipse of the Moon is called a lunar eclipse, and it occurs when the Earth prevents the Sun from shining on the Moon.

During a lunar eclipse, Earth comes between the Sun and the Moon and blocks the sunlight from falling on the Moon. Earth’s shadow covers all or part of the surface of the Moon. There are two kinds of lunar eclipses:

1. A Total Lunar Eclipse

It occurs when the Moon and Sun are on opposite sides of Earth.

2. A Partial Lunar Eclipse

It occurs when only part of Earth’s shadow covers the Moon.

Blood Moon

During a full lunar eclipse, the Moon can appear red. This can happen when a little bit of light from Earth’s sunrises and sunsets falls on the surface of the Moon. When the light waves stretch out, they look red, and when the red light falls on the Moon’s surface, it appears red. We call this a “Blood Moon”. 

Blood Moon

Exploration

People have observed the Moon since ancient times because it is the brightest object in the night sky. After the invention of the telescope, people became able to study the Moon more closely. Before people stood on the Moon, the United States and the Soviet Union sent robots to the Moon. Some robots orbited the Moon and some landed on its surface. Since 1959, many spacecraft have been sent to the Moon. The first unmanned spacecraft to land on the Moon successfully was Luna 9, which was sent by the Soviet Union in 1966. 

Humans landed on the Moon on July 21, 1969. The U.S. Apollo 11 craft carried Astronauts Neil Armstrong and Buzz Aldrin to the surface of the moon. Then, Armstrong climbed down the ladder of the spacecraft and was the first human to touch the Moon.

Ten other people have walked on the Moon since then. The last person to touch the Moon was Eugene Cernan of Apollo 17, which was the last spaceship to visit the Moon. 

What Does the Moon Do?

The Moon is close to Earth enough to affect it in many ways; for example: 

  • The gravity of the Moon pulls on Earth. It is too weak to affect the whole planet, but it makes the water in seas and oceans move, which creates the tides. 
  • The pull of the Moon causes the Earth’s rotation to slow down. As a result, the length of our day increases by 2.3 milliseconds per century. Scientists say that in around 200 million years, a day on our planet will be 25 hours long.
  • The Moon picks up the energy that Earth loses. As a result, the distance between the Moon and Earth increases. The moon gets farther away by 1.5 inches (3.8 centimetres) every year.
  • The Moon makes Earth a more livable planet by moderating its wobble on its axis, leading to a stable climate in which life could flourish. 

17 Interesting Facts about the Moon

  1. The Moon is the second brightest object in our sky after the Sun, and the brightest object in the night sky.
  2. The Moon is the only place beyond Earth where humans have set foot. 
  3. It is simply called “the Moon” because people did not know any other moons until Galileo Galilei discovered four moons orbiting planet Jupiter in 1610. 
  4. The Moon is shaped like an egg.
  5. The Moon is bigger than Pluto.
  6. The Moon orbits the Earth as fast as a rifle bullet.
  7. It takes a spacecraft about 3 days to reach the Moon.
  8. We only see around 60% of the Moon’s surface from Earth.
  9. Just like the Sun, the Moon rises in the east and sets in the west.
  10. There is no air resistance on the Moon because there is no atmosphere surrounding it, so a feather will fall as fast as a hammer.
  11. The footprints of the astronauts of Apollo are still there on the Moon. This is because there is no wind or rain, so there is no erosion on the Moon. 
  12. A solar eclipse can only happen at new moon.
  13. A lunar eclipse can only happen at full moon.
  14. During a “blood moon” lunar eclipse, an observer from there would see all Earth’s sunrises and sunsets at once.
  15. Most scientists believe that there is water on the Moon, but they are still researching. 
  16. The only month that can occur without a full moon is February.
  17. The Moon does not produce its own light, and we see it only because it reflects light from the Sun. So, if the Sun was not there, we would not be able to see the Moon. 

What is the biggest planet in the Solar System? The answer for this question would be “Jupiter”.

Jupiter is the fifth planet from the Sun, between Mars and Saturn. It is the biggest planet in the solar system. In fact, Jupiter is so big that it could easily swallow all of the other planets around it in the solar system.

Jupiter is considered a gas giant. This is because it consists of gas. In fact, Jupiter is very similar to a star, but it has never got big enough to start burning as stars do. The average distance between Jupiter and the Sun is about 778 million kilometers.

Surface and Structure

Jupiter is one of the gas giant planets. This kind of planet consists almost entirely of gases. The main two gases that Jupiter consists of are hydrogen and helium. Jupiter has no solid surface. Instead, it has layers of clouds that appear in colored spots and bright and dark stripes. One of those spots is a huge storm called the Great Red Spot. Deep inside Jupiter, the pressure increases so much that it turns hydrogen gas into liquid, and then into metal. This area is so hot and thick, and it may reach temperatures of 45,000° F (25,000° C). Finally, there is a rocky core under the hydrogen, and it is about the size of Earth

Atmosphere

Jupiter has a huge and thick atmosphere. In fact, it is the largest atmosphere of a planet in the Solar System. It consists mostly of molecular hydrogen and helium. It also contains small amounts of many other gases, including methane, ammonia, hydrogen sulfide, water vapor, and nitrogen.

Clouds form in the lower parts of Jupiter’s atmosphere. The temperature there gets colder when moving high above the planet. The middle and upper levels of the atmosphere are hotter because the gases absorb solar radiation. The clouds appear in dark and bright colors. Scientists think that they vary in color because they contain different chemicals.

The atmosphere of Jupiter is also stormy and unstable. The clouds form and change within hours or days. However, the wind currents have been stable for more than decades. Strong winds blow east or west through the atmosphere, and they are sometimes interrupted by large storms that appear from above as ovals. 

The Great Red Spot

The most constant feature in the atmosphere of Jupiter is the Great Red Spot. It has been observed from Earth continuously since 1878, and it may even be the same storm that was observed from 1665 to 1713. The spot is a huge storm in the shape of an oval in the southern hemisphere of Jupiter. It has strong winds that swirl counterclockwise about a center in which the pressure is so high.

The Great Red Spot covers a huge area that is larger than Earth itself. It is about 16,500 kilometers wide, and it has been shrinking since the late 19th century. Since 2012, the Great Red Spot has become more circular and has been shrinking faster. It loses about 900 kilometers in width each year.

Jupiter

Temperature

The source of temperature on Jupiter is its inner part, not the Sun. So, the temperature on Jupiter depends on the height from the surface. The average temperature on Jupiter is -145 °C (-234 °F). Near the center of the planet, the temperature is very high and may be about 24,000 °C (43,000 °F) at the core, which is hotter than the Sun’s surface. About 50 kilometers above the surface, the temperature decreases and ranges from -100 °C (-150 °F) to -160 °C (-260 °F). In the clouds of Jupiter, the temperature is about -145 °C (-234 °F).

Size

Jupiter is the largest planet in the Solar System. It is so huge that it could contain more than 1,000 Earths. Its diameter is about 143,000 kilometers. This is more than 11 times the diameter of Earth, and more than 29 times the diameter of Mercury. More than 24,000 Mercury’s would fit inside Jupiter. 

Planets in the Solar System
This picture shows the size of Jupiter compared to other planets

Orbit and Rotation

Like other planets, Jupiter has two types of motion: orbit around the Sun and spin about its centre. Jupiter orbits the Sun very slowly. It takes about 12 Earth years to complete one orbit, so a year on Jupiter lasts about 12 Earth years. On the contrary, Jupiter rotates, or spins, rapidly about its center. It takes less than 10 hours to complete one rotation, so a day on Jupiter lasts less than 10 hours.

Moons

Jupiter has 79 known moons. It has the second largest number of moons with stable orbits of any planet in the Solar System. Most of Jupiter’s moons are very small. However, it has four very large moons: Io, Europa, Callisto, and Ganymede. Those four massive moons are called Galilean moons, and they were discovered in 1610 by Galileo Galilei. They were the first discovered objects to orbit a body in the Solar System other than Earth and the Sun.

Ganymede is larger than the planet Mercury, and it has its own magnetic field. Scientists believe that Europa and Ganymede may have water ice beneath their surfaces. Io is the most volcanic body in the solar system. 

Rings

Jupiter has 3 ring systems surrounding it. They are thin and very faint and hard to see. The rings consist of rocks and tiny rocks. They are much smaller and dimmer than the rings of the planet Saturn.

Name

Planet Jupiter is named after the Roman god “Jupiter”, who was the king of gods. To the ancient Greeks, he was known as Zeus, and they believed that it was their most powerful god. The Romans gave this name to the planet because of its huge size.

Discovery and Exploration

People have observed Jupiter from Earth since ancient times because it can be seen without a telescope. 

In 1973, scientists sent a space probe called Pioneer 10 to explore Jupiter. The probe flew by the planet and collected information about it. They also sent another one called Pioneer 11. 

After the Pioneer probes, NASA sent other probes called Voyager 1 and 2. They gave us the first close up shots of Jupiter’s moons. Since then, there have been many more probes to fly by Jupiter. 

The only spacecraft that has orbited Jupiter was the Galileo in 1995. It dropped a probe toward Jupiter that sailed through the layers of gases and collected information about them. It was the first human-made object to make contact with a gas giant planet.

probes around Jupiter

13 Interesting Facts About the Biggest Planet: Jupiter

  1. Jupiter is bright in our night sky, and it is actually the third brightest objects, after the Moon and Venus.
  2. Jupiter is one of the five visible planets from Earth. The others are Mercury, Venus, Mars and Saturn.
  3. Jupiter is the most massive planet in the Solar System. Its mass is almost twice of all the Solar System’s planets combined. Its Mass is around 318 times larger than that of Earth.
  4. Some astronomers consider Jupiter a failed star because of its mass. 
  5. If Jupiter would be more massive than it currently is, it would become a star just like the Sun.
  6. Jupiter generates high amounts of heat because it is so massive. The heat it generates is actually more than the heat it receives from the Sun.
  7. Because of the large amount of heat it radiates, Jupiter shrinks about 2 centimetres every year. Scientists do not know when it will stop shrinking.
  8. Every 13 months, Jupiter comes closer to us and becomes very bright in the night sky.
  9. Jupiter is like a vacuum cleaner to the Solar System. Its powerful gravity attracts many of the comets and asteroids to hit it rather than other planets. Jupiter is exposed to the impacts of asteroids and comets 200 times more than Earth is.
  10. There are dangerous waves of radiation surrounding Jupiter that make it hard for spacecraft to approach the planet.
  11. If you would weigh 100 pounds on Earth, on Jupiter you would weigh 240 pounds because of the gravitational force. So, on Jupiter, you would weigh 2.5 times more than on Earth.
  12. Scientists believe that there are many chances for Jupiter’s moon Europa to develop and support life.
  13. A space journey from Earth to Jupiter takes about 13 months.