The Sun and the life of a star Edexcel International GCSE Science (Single Award) revision
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In plain words
A star is born when gravity pulls a huge cloud of gas and dust together until the middle is hot enough for hydrogen nuclei to fuse. That fusion keeps it shining for billions of years. What happens at the end depends on its size: stars like the Sun swell into red giants and then shrink to white dwarfs; giant stars explode as supernovae.
Three things to know
- The Sun is a medium-sized star made mostly of hydrogen and helium. It is powered by nuclear fusion of hydrogen into helium, and gives out most of its energy as infrared, visible light and ultraviolet.
- A star forms when gravity pulls a cloud of gas and dust (a nebula) together until it is hot enough for fusion to start. It is then stable for a long time: the outward pressure balances gravity.
- A star like the Sun later becomes a red giant, then a white dwarf. A much bigger star becomes a red supergiant, explodes as a supernova and leaves a neutron star or a black hole.
Tips and tricks
- Learn the two life stories as chains. A star like the Sun: nebula → main sequence star → red giant → white dwarf. A much bigger star: nebula → main sequence star → red supergiant → supernova → neutron star or black hole.
- A star is stable for most of its life because two things balance: gravity pulling in, and the pressure of the hot gas pushing out.
It lands in your notebook with its questions as flashcards.
The Sun and the life of a star: 6 questions and answers
These are the quiz’s questions. Do the quiz first, then come back here for the ones that got you.
What provides the energy of a star during most of its life?
Hydrogen nuclei fuse to make helium.
What will a star about the size of the Sun end as?
Only much more massive stars explode as supernovae.
What is a nebula?
Stars form when gravity pulls a nebula together.
What is the Sun mostly made of?
Like other stars, it is mostly hydrogen with some helium.
What can be left behind after a supernova?
The collapsed core of a very massive star is extremely dense.
What pulls the gas and dust of a nebula together to form a star?
Gravity acts between all the particles in the cloud.
Quiz
6 questions
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Worksheet
4 questions, 10 marks. Write your answers on paper, then check them.
The Sun and the life of a star
Edexcel International GCSE Science (Single Award) 4SS0 · 10 marks · papermunch.org
Name ______________________________ Date ______________
Describe how a star like the Sun is formed.[3]
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A cloud of gas and dust is pulled together by gravity. It heats up as it collapses until hydrogen nuclei start to fuse.
State what the Sun will become after its red giant stage.[2]
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A white dwarf.
Explain why a star is stable for most of its life.[2]
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The inward pull of gravity is balanced by the outward pressure from the hot gas (from fusion).
Describe what happens at the end of the life of a star much more massive than the Sun.[3]
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It swells into a red supergiant, then explodes as a supernova. The core left behind becomes a neutron star, or a black hole if it is massive enough.
Answers: The Sun and the life of a star
- 1. A cloud of gas and dust is pulled together by gravity. It heats up as it collapses until hydrogen nuclei start to fuse.
- 2. A white dwarf.
- 3. The inward pull of gravity is balanced by the outward pressure from the hot gas (from fusion).
- 4. It swells into a red supergiant, then explodes as a supernova. The core left behind becomes a neutron star, or a black hole if it is massive enough.