Extension: The Sun, Our Star Up Close
Every clear morning across Australia, from Bondi Beach to the red sand of the outback, the same star rises and floods the country with light and warmth. The Sun looks small in the sky, but it is by far the largest object in our Solar System and the source of almost all the light and heat on Earth. In this bonus lesson you will zoom in on our local star: what it is made of, the layers inside it, the storms on its surface, and how it makes its enormous energy deep in its core. You will also learn the most important rule about the Sun: never look straight at it.
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This is an extension lesson. It goes beyond the Stage 4 syllabus dot points for interest and enrichment. You will not be tested on it in the same way as the core lessons, but it builds on what you have learned about the Sun, Earth and Moon, and it is great background for any future space science.
Q1 · In your own words, what is the Sun? Is it solid like Earth, or something different? Write down what you already think it is made of.
Q2 · The Sun gives Earth light and heat. Where do you think the Sun gets all that energy from, and why do you think it has not run out yet?
● Know
- The Sun is a star, a giant ball of hot glowing gas called plasma, and the largest object in the Solar System
- The Sun has rough layers: a core where energy is made, a surface we see called the photosphere, and an outer glow called the corona
- The Sun makes its energy by joining hydrogen into helium deep in its core, a process called nuclear fusion
● Understand
- Why the Sun is the source of almost all the light and heat on Earth
- How sunspots and solar flares are signs of activity on the Sun
- Why the Sun is described as middle-aged, at about 4.6 billion years old
● Can do
- Describe the Sun and name its main layers in simple terms
- Explain in your own words how the Sun makes its energy
- State the safety rule for observing the Sun and explain why it matters
When you look up at the night sky you see thousands of stars, all of them so far away they look like tiny dots. The Sun is also a star, but it is special to us for one reason: it is the closest star to Earth. Because it is so close, it looks like a huge bright disc instead of a dot. The Sun is by far the largest object in our Solar System, and it is the source of almost all the light and heat that reaches Earth.
Here are some things that make the Sun amazing:
- The Sun is not solid. It is a giant ball of super hot gas called plasma, which is gas so hot that it glows brightly.
- The Sun is enormous. About 1.3 million Earths could fit inside it.
- Almost all of Earth's light and warmth comes from the Sun. Plants use sunlight to grow, and that food then feeds nearly every living thing.
- In Australia, where many sunny days fall each year, we even use the Sun's energy directly through solar panels on rooftops and in large solar farms.
So the Sun is not just a light in the sky. It is the engine that powers life on our planet, and it is a star we get to study from up close.
The Sun is not the same all the way through. Scientists describe it in rough layers, a bit like an onion. You do not need to remember every detail, but three layers are easy to picture.
- The core: the centre of the Sun, where it is hottest and the pressure is huge. This is the place where the Sun makes its energy.
- The photosphere: the bright surface we actually see from Earth. The word means the layer of light. This is the glowing yellow disc you must never look at directly.
- The corona: the faint outer glow that spreads far out around the Sun. We usually cannot see it because the bright photosphere outshines it, but it becomes visible during a total solar eclipse.
Energy is made in the core, then it slowly works its way outward until it leaves the surface as the light and heat that travels to Earth.
- Core
- Photosphere
- Corona
- The hot centre where the Sun makes its energy
- The bright surface we see from Earth
- The faint outer glow, seen during a total solar eclipse
The Sun is not calm and still. Its surface is always churning and changing, and sometimes we can see signs of this activity.
- Sunspots are dark patches on the photosphere. They look dark because they are a little cooler than the gas around them, though they are still extremely hot. Sunspots can be larger than the whole Earth, and they come and go over weeks.
- Solar flares are sudden bursts of energy that shoot out from the Sun, often near sunspots. A big flare can send a stream of particles toward Earth.
When those particles reach Earth, they can create the beautiful glowing lights in the sky called auroras. In Australia these southern lights are known as the aurora australis, and they are sometimes seen from Tasmania and southern Victoria. Strong solar activity can also disturb radio signals and satellites, so scientists watch the Sun closely.
Important note: scientists study sunspots and flares using special equipment with strong filters. You must never try to look at sunspots yourself with your bare eyes, binoculars or a telescope.
Dark patches on the Sun's surface are called ___. They look dark because they are slightly ___ than the gas around them. Sudden bursts of energy from the Sun are called solar ___. When their particles reach Earth they can create glowing lights called ___.
The Sun has been shining for billions of years, so where does all that energy come from? The answer lies deep in the core, where it is incredibly hot and the pressure is crushing.
In the core, tiny bits of hydrogen (the lightest and most common gas in the Sun) are squeezed together so hard that they join up to make a slightly heavier gas called helium. This joining together of small bits into bigger ones is called nuclear fusion. Each time it happens, a little burst of energy is released. Because this is going on countless times every second across the core, the total energy is enormous, and it streams outward as the light and heat we feel on Earth.
The Sun has plenty of hydrogen fuel left. It is about 4.6 billion years old, which sounds ancient, but for a star like the Sun that is only middle-aged. It is expected to keep shining steadily for billions of years more.
The Sun is wonderful to study, but it is also dangerous to look at. Its light is so strong that it can permanently damage your eyes in seconds, and you would not even feel the harm happening at the time.
The most important rule in this whole lesson is simple:
- Never look directly at the Sun, especially through binoculars or a telescope. These devices focus the Sun's light and can blind you almost instantly.
- Normal sunglasses are not safe for looking at the Sun. They are made for everyday brightness, not for staring at a star.
- To watch a solar eclipse safely, use special eclipse glasses that meet the proper safety standard, or use an indirect method like a pinhole projector that shows the Sun on a card.
Astronomers in Australia, such as those who study the Sun with special filtered telescopes, always use proper safety equipment. Studying the Sun is exciting, but protecting your eyes always comes first.
The Sun has been shining for about 4.6 billion years and is expected to keep going for billions more. A campfire would burn out in hours, and even a huge coal fire would not last anywhere near that long. Predict: why can the Sun keep producing energy for such an enormous length of time, when ordinary fires run out so quickly?
How close was your prediction?
At the start of the lesson you wrote your own idea of what the Sun is and where it gets its energy. Now write an improved, complete answer.
Your answer must: (1) describe what the Sun is and what it is made of; (2) name its main layers; (3) explain in simple terms how it makes its energy. Use the words star, plasma, core and nuclear fusion.
Q1. Describe what the Sun is and what it is made of, and explain why it is so important for Earth. (3 marks)
Q2. Name the three main layers of the Sun and write one thing about each one. (3 marks)
Q3. A friend wants to watch a solar eclipse and says they will just look straight up with their normal sunglasses. Explain why this is unsafe and describe one safe way to watch instead. (3 marks)
Answers
▾MCQ 1
B. The Sun is a star, a giant ball of hot glowing gas called plasma. It is not a solid rock, not a planet, and it makes its own light rather than reflecting it.
MCQ 2
C. Energy is made in the core, the hot centre of the Sun. The photosphere is the surface we see, and the corona is the faint outer glow.
MCQ 3
D. Sunspots look dark because they are slightly cooler than the gas around them, though they are still very hot. They are not holes, rocks or planet shadows.
MCQ 4
A. In nuclear fusion, hydrogen joins together to make helium deep in the Sun's core, and this releases energy. The Sun does not burn fuel like coal, store other stars' light, or heat up from spinning.
MCQ 5
C. The safe rule is never to look directly at the Sun, especially through binoculars or a telescope, which focus its light and can blind you. Squinting and ordinary sunglasses do not protect your eyes.
Short Answer 1
Model answer: The Sun is a star, the closest one to Earth. It is a giant ball of hot glowing gas called plasma, and it is the largest object in our Solar System. It is important for Earth because it is the source of almost all the light and heat we get, which plants need to grow and which keeps the planet warm enough for life.
Short Answer 2
Model answer: The core is the hot centre where the Sun makes its energy. The photosphere is the bright surface we see from Earth. The corona is the faint outer glow that spreads around the Sun and can be seen during a total solar eclipse.
Short Answer 3
Model answer: Looking straight at the Sun is unsafe because its light is so strong it can permanently damage the eyes in seconds, and ordinary sunglasses are not made to block that much light. A safe way to watch an eclipse is to use special eclipse glasses that meet the proper safety standard, or to use an indirect method such as a pinhole projector that shows the Sun on a card.