The Sun is not a planet; it is a star, and understanding the difference is one of the most important early lessons in the UK Year 5 Earth and Space curriculum. Yet the question “is the Sun a planet?” remains one of the most searched-for space queries in UK primary classrooms, suggesting that the distinction between stars and planets is genuinely confusing for young learners.
At LearningMole, we believe that clearing up this misconception early gives children a solid foundation for all the space science that follows. This article answers that question directly, then takes children aged 7–11 on a journey through the Sun’s structure, its staggering size, the energy it produces, and why life on Earth simply could not exist without it.
Whether you are a parent looking for clear, curriculum-aligned explanations or a teacher planning a Year 5 Earth and Space lesson, this guide covers everything in one place. LearningMole’s approach draws on the UK National Curriculum and the expertise of experienced educators to make complex science feel approachable and memorable. You will find the 7 layers of the Sun explained in plain language, 20 carefully chosen facts grouped into themes, a Sun vs Earth comparison table, and practical classroom and home learning ideas drawn from LearningMole’s library of video and activity resources.
By the end of this article, every child who reads it will be able to answer confidently: the Sun is a G-type main-sequence star, the centre of our Solar System, and the reason every living thing on Earth has light, warmth, and oxygen. That is a powerful piece of scientific understanding, and it is exactly the kind of knowledge that LearningMole is built to deliver.
The Sun is a star, not a planet — and the single most important difference between the two comes down to light: stars produce their own, while planets only reflect it.
The Sun is classified as a G-type main-sequence star, sometimes called a Yellow Dwarf. It sits at the centre of our Solar System and has done so for approximately 4.5 billion years. It is currently about halfway through its expected lifespan, meaning it still has around 5 billion years of fuel left.
A planet is a body that orbits a star, has enough gravity to pull itself into a roughly spherical shape, and has cleared the neighbourhood around its orbit. The Sun meets none of these criteria. Instead, every planet, comet, and asteroid in our Solar System orbits the Sun — it is the gravitational anchor around which everything else moves.
The most fundamental reason the Sun is not a planet is nuclear fusion. Deep inside the Sun’s core, hydrogen atoms are fused together under enormous pressure and temperature to form helium. This process releases a colossal amount of energy in the form of heat and light — the same heat and light we feel on Earth every day. Planets cannot do this. They are too small and lack the internal pressure and temperature needed to trigger nuclear fusion. A planet like Jupiter would need to be approximately 80 times more massive before it could begin to fuse hydrogen and become a star.
In summary: a star produces its own light through nuclear fusion; a planet reflects the light of its host star. The Sun produces light. The Earth, Mars, and all the other planets in our Solar System do not — they shine only because the Sun illuminates them.
| Feature | The Sun (a Star) | The Earth (a Planet) |
|---|---|---|
| Produces own light? | Yes — through nuclear fusion | No — reflects sunlight |
| Orbits another object? | No — everything orbits it | Yes — orbits the Sun |
| Made of? | Plasma (hydrogen and helium gas) | Solid rock, liquid water, gas atmosphere |
| Age | ~4.5 billion years | ~4.5 billion years |
| Diameter | ~1,392,000 km | ~12,742 km |
| Core temperature | ~15 million °C | ~5,200 °C |
| Surface temperature | ~5,500 °C (photosphere) | ~15 °C (average surface) |
The Sun is made up of 7 distinct layers, each with its own temperature, density, and role in generating and releasing the energy that warms our planet.
The Sun is not a solid object. It is a churning ball of plasma, a superheated state of matter in which electrons are stripped from their atoms, held together entirely by its own gravity. Understanding its layers helps explain how energy born in the very centre of the Sun eventually reaches a child’s bedroom window 150 million kilometres away.
LearningMole’s science video resources cover the solar system in depth for Key Stage 2 learners. You can explore the full range of Earth and Space resources on the LearningMole website, where video lessons and activity packs align with Year 5 and Year 6 curriculum objectives.
The core is the innermost layer of the Sun and its energy source. Temperatures here reach approximately 15 million °C, and the pressure is so extreme that nuclear fusion occurs constantly. Every second, the Sun fuses around 600 million tonnes of hydrogen into helium. The energy produced does not escape immediately — it begins a journey outward through the Sun’s layers that can take between 10,000 and 170,000 years before it finally reaches the surface.
Surrounding the core, the radiative zone is where energy travels outward as radiation — photons of light bouncing from atom to atom in an extraordinarily slow, zigzagging journey. The temperature drops from around 7 million °C at the inner boundary to about 2 million °C at the outer boundary of this zone.
In the convective zone, the plasma is no longer hot enough to transfer energy by radiation alone. Instead, hot plasma rises toward the surface, cools, and sinks back down — the same convection process you can observe in a pot of boiling water. This zone extends from about 200,000 km below the surface all the way to the photosphere.
The photosphere is the layer we see when we look at the Sun (through appropriate solar filters — never with the naked eye). It is described as the visible surface of the Sun, with a temperature of around 5,500 °C. It is also where sunspots appear: darker patches caused by concentrations of the Sun’s magnetic field that are slightly cooler than the surrounding plasma.
Just above the photosphere, the chromosphere is a thin, reddish layer of plasma normally invisible to the naked eye. Unusually, temperatures in the chromosphere increase with altitude, rising to around 20,000 °C at its outer edge — the opposite of what you would expect. This temperature reversal is one of the great unsolved puzzles in solar physics.
The transition region is a thin boundary layer where temperatures leap dramatically from around 20,000 °C to over 1 million °C in a very short distance. Scientists are still working to understand precisely why this jump occurs so abruptly.
The corona is the Sun’s outermost atmosphere, stretching millions of kilometres into space. Its temperature can reach several million degrees Celsius, far hotter than the surface below, which is another phenomenon scientists are actively researching. The corona is normally invisible from Earth but becomes dramatically visible during a total solar eclipse as a halo of white light around the darkened Moon. The corona is also the source of the solar wind: a continuous stream of charged particles that flows throughout the entire Solar System.
These 20 facts are grouped into four themes to make them easier to remember, discuss in class, or use as the basis for a home learning activity.
Jump to Size and Scale | Jump to Heat and Energy | Jump to Surface and Atmosphere | Jump to The Sun and Our Solar System
Fact 1. The Sun’s diameter is approximately 1,392,000 kilometres — about 109 times wider than Earth. If the Earth were the size of a 1p coin, it would be approximately the size of a football.
Fact 2. More than 1.3 million Earths would fit inside it. Despite this, the Sun is considered a medium-sized star. Red giant stars like Betelgeuse dwarf our Sun by comparison.
Fact 3. It contains about 99.8% of all the mass in the entire Solar System. Everything else — all eight planets, every moon, asteroid, and comet — makes up just the remaining 0.2%.
Fact 4. It is approximately 150 million kilometres from Earth. This distance is so significant that it has its own unit of measurement: one Astronomical Unit, or AU.
Fact 5. Despite being 150 million kilometres away, the Sun’s light reaches Earth in just 8 minutes and 20 seconds, travelling at 299,792 kilometres per second. If our Sun were suddenly switched off, we would not notice for over 8 minutes.
Fact 6. The Sun’s core temperature reaches approximately 15 million °C. The surface temperature (the photosphere) is a comparatively cool 5,500 °C.
Fact 7. Every second, it converts around 4 million tonnes of mass directly into energy through nuclear fusion. Einstein’s famous equation E=mc² describes exactly this process.
Fact 8. The energy produced in the Sun’s core takes between 10,000 and 170,000 years to travel from the core to the photosphere. Once it reaches the surface, it travels to Earth in just over 8 minutes.
Fact 9. It fuses approximately 600 million tonnes of hydrogen into helium every single second. It has enough hydrogen fuel remaining to continue this process for approximately another 5 billion years.
Fact 10. The Sun’s true colour is white, not yellow. We perceive it as yellow because Earth’s atmosphere scatters shorter wavelengths of light. From space, astronauts see it as brilliantly white.
Fact 11. Sunspots are darker, cooler areas on the photosphere caused by concentrations in the Sun’s magnetic field. They are temporary, lasting from a few days to several months, and appear in cycles of approximately 11 years.
Fact 12. Solar flares are sudden, intense bursts of energy from the Sun’s surface. They release radiation across the electromagnetic spectrum and can affect satellites and communications technology on Earth.
Fact 13. The corona — the Sun’s outermost atmosphere — reaches temperatures of several million degrees Celsius, far hotter than the photosphere below it. This phenomenon, known as the coronal heating problem, remains one of astronomy’s most active areas of research.
Fact 14. The solar wind — charged particles streaming outward from the corona — travels through the entire Solar System at speeds of around 400–800 kilometres per second. When it interacts with Earth’s magnetic field, it produces the Northern and Southern Lights (auroras).
Fact 15. A total solar eclipse occurs when the Moon passes directly between our Sun and Earth, temporarily blocking the Sun’s light. These events allow scientists to study the corona without special instruments and are one of the most spectacular natural phenomena visible from Earth’s surface.
Fact 16. It is the only star in our Solar System. The next closest star to Earth is Proxima Centauri, which is approximately 4.24 light-years away — so distant that its light takes over four years to reach us.
Fact 17. It rotates, but because it is made of plasma rather than solid matter, different latitudes rotate at different speeds. The equator takes about 25 days to complete one rotation, while the poles take about 35 days.
Fact 18. It orbits the centre of the Milky Way galaxy. At its orbital speed of approximately 220 kilometres per second, it takes our Sun around 230 million years to complete one full orbit — a period sometimes called a Galactic Year.
Fact 19. Ultraviolet (UV) radiation from the Sun enables human skin to produce vitamin D, which is essential for healthy bones and immune function. The same UV radiation causes sunburn when exposure is unprotected and prolonged.
Fact 20. In approximately 5 billion years, it will exhaust its hydrogen fuel. It will then expand into a red giant, potentially engulfing the inner planets, before eventually collapsing into a small, dense white dwarf star.
Our Sun is not simply a source of warmth and daylight — it is the fundamental driver of almost every natural system on Earth, from weather and ocean currents to food chains and the oxygen we breathe.
Since ancient times, civilisations have recognised the Sun’s importance. Ancient Egyptians worshipped Ra, their sun god, understanding intuitively that life depended on this brilliant presence in the sky. Modern science has given us the precise mechanisms behind what those early observers sensed — and the picture is even more extraordinary than they imagined.
Here are ten ways the Sun sustains life on Earth:
It provides the light needed for photosynthesis — the process by which plants convert sunlight into food. Without photosynthesis, the entire food chain collapses, because plants form the foundation of almost all life on Earth.
As a by-product of photosynthesis, plants release oxygen into the atmosphere. The oxygen we breathe has been produced by plants powered by sunlight over billions of years.
The Sun’s heat drives the water cycle. Solar energy evaporates water from oceans, lakes, and rivers; that water vapour rises, cools, and condenses into clouds; eventually it falls as rain or snow, replenishing freshwater supplies and maintaining ecosystems.
It drives Earth’s weather systems. Uneven heating of the Earth’s surface creates differences in air pressure that generate wind. Those winds move weather systems, distribute moisture, and regulate temperature across continents.
The Sun’s energy heats the oceans, creating currents that distribute warmth around the globe. The Gulf Stream, which keeps the UK’s climate milder than its latitude would otherwise suggest, is ultimately powered by the Sun.
It enables the seasons. Earth’s axial tilt means different hemispheres receive more or less direct sunlight at different times of year — creating the seasonal changes that govern agriculture, animal migration, and ecological cycles.
Our Sun provides ultraviolet radiation that the human body uses to synthesise vitamin D, essential for calcium absorption, bone health, and immune system function.
Solar energy is the basis for renewable electricity generation. Solar panels convert sunlight directly into electricity, offering a sustainable alternative to fossil fuels.
Fossil fuels, coal, oil, and natural gas are themselves ancient stores of solar energy, captured by prehistoric plants and organisms through photosynthesis and then compressed over millions of years.
The Sun’s gravity holds the entire Solar System together. Without it, Earth and all the other planets would fly off into interstellar space.
Studying our Sun directly supports the Year 5 Earth and Space unit of the UK National Curriculum, helping children aged 9–11 build scientific vocabulary and develop their understanding of the wider universe.
The Year 5 programme of study requires children to describe the movement of Earth and other planets relative to the Sun, describe the movement of the Moon relative to Earth, and explain day and night using the concept of Earth’s rotation. Understanding what it actually is — a star, a ball of plasma sustained by nuclear fusion, the gravitational centre of the Solar System — provides the foundational knowledge from which all these concepts grow.
“Children absorb astronomical concepts far more readily when they have a vivid mental model to work from,” says Michelle Connolly, Founder of LearningMole and a former classroom teacher with over 16 years’ experience. “Explaining that the Sun’s core energy takes longer to escape than modern humans have existed on Earth is exactly the kind of concrete, surprising comparison that makes the abstract feel real.”
LearningMole’s science video resources are mapped to Key Stage 2 curriculum objectives, giving teachers a reliable, curriculum-aligned supplement to classroom instruction. The Solar System facts article and Planets for Kids guide extend this topic across related areas of the Year 5 and Year 6 programmes of study.
LearningMole offers a library of curriculum-aligned video lessons, activity packs, and printable resources that support teaching and home learning about the Sun and the wider Solar System.
For classroom use, LearningMole’s video resources explain solar system concepts in child-friendly language, with clear visuals designed to build understanding progressively. The videos are particularly effective as lesson starters or as consolidation activities following direct teaching.
For home learning, LearningMole’s subscription gives families access to over 1,000 educational videos covering science, mathematics, English, and more — all aligned with the UK National Curriculum. Parents can use the Sun and Solar System content to extend learning during school holidays, prepare children for upcoming topics, or revisit concepts that need reinforcement.
You can access LearningMole’s full video library and download teaching resources by visiting learningmole.com. Subscription plans start from £1.99 per month, making it accessible for families and classroom teachers alike.
The Sun is not a planet because it produces its own light and energy through nuclear fusion, a process that requires the enormous mass and gravitational pressure only a star possesses. Planets are far smaller and have no capacity for nuclear fusion. They shine only by reflecting the light of their host star. The Sun also does not orbit another object; instead, everything in our Solar System orbits the Sun.
No. The Sun is a medium-sized star classified as a Yellow Dwarf. While it is by far the largest object in our Solar System, many stars are considerably larger. Red supergiants such as Betelgeuse and Antares would dwarf the Sun if placed at the centre of our Solar System — Betelgeuse, if substituted for the Sun, would extend beyond the orbit of Jupiter. The Sun’s size is, in fact, fairly typical for the stars in our region of the Milky Way.
Approximately 1.3 million Earths would fit inside the Sun if packed tightly together. If you compare just diameters, the Sun is about 109 times wider than Earth. These figures help explain why the Sun contains 99.8% of all the mass in the Solar System.
The Sun is made almost entirely of hydrogen (about 73% by mass) and helium (about 25% by mass), with tiny amounts of heavier elements making up the rest. In the Sun’s core, hydrogen is continuously fused into helium through nuclear fusion, releasing the energy that powers the Sun. The Sun exists as plasma — a state of matter in which the gas is so hot that electrons are separated from their atomic nuclei.
If the Sun were suddenly extinguished, we would not know for 8 minutes and 20 seconds — the time it takes sunlight to reach Earth. After that, daylight would disappear. Within weeks, average surface temperatures would drop below −17 °C. Within a year, they would plummet to around −73 °C. Photosynthesis would cease, eliminating the base of almost every food chain on Earth. The oceans would begin to freeze over. Deep-sea hydrothermal vent ecosystems might persist for some time, but life as we know it on the surface would not survive.
No. The Moon is a natural satellite, a body that orbits a planet rather than a star directly. It orbits Earth and shines only by reflecting sunlight. To qualify as a planet under the International Astronomical Union’s definition, a body must orbit the Sun directly, have sufficient mass for self-gravity to make it roughly spherical, and have cleared the neighbourhood around its orbit. The Moon meets none of these criteria.
In theory, yes — but it would need to gain an enormous amount of mass. A planet would need to increase its mass by approximately 80 times the mass of Jupiter before it became massive enough for the core pressure and temperature to trigger hydrogen fusion. At that point, it would ignite as a small red dwarf star. Jupiter, the largest planet in our Solar System, is only about 0.1% of the mass of the Sun — so while the concept is scientifically valid, no planet in our Solar System is remotely close to that threshold.
The Sun emits light across the full visible spectrum, which, when combined, appears white. However, Earth’s atmosphere scatters shorter wavelengths of light, particularly blue light, in all directions, creating the blue sky we see during the day. The remaining light that travels directly from the Sun to our eyes has proportionally more of the longer, warmer wavelengths (yellow, orange, red), making the Sun appear yellow or orange, especially near the horizon. From space, where there is no atmosphere to scatter any wavelengths, the Sun appears brilliantly white.
The Sun is one of the most captivating topics in primary science, and it connects directly to some of the biggest questions children ask about the universe. Why is the sky blue? Why do we have seasons? What holds the planets in their orbits? All of these questions lead back, in one way or another, to our nearest star.
LearningMole has designed its science resources specifically to build on children’s natural curiosity, turning questions like “Is the Sun a planet?” into springboards for deeper understanding. If this article has sparked an interest in space, the Solar System facts guide and Planets for Kids resource are natural next steps — both aligned to the UK National Curriculum and written with the same commitment to clarity and accuracy that runs through everything LearningMole produces.
Explore the full LearningMole science library at learningmole.com and discover curriculum-aligned video lessons, downloadable activity packs, and home learning resources that make science memorable for children aged 3–11.
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