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Year 11
AQA
Higher

Stellar evolution

I can describe life cycles of stars and the variations that depend on the mass of a star.

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New
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Year 11
AQA
Higher

Stellar evolution

I can describe life cycles of stars and the variations that depend on the mass of a star.

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Lesson details

Key learning points

  1. Radiation pressure from nuclear fusion pushes out from the centre of a star.
  2. Gravitational force pulls in towards the centre of a star.
  3. When a star is in balance, forces from radiation pressure are equal in size to gravitational forces.
  4. A main sequence star is a star in balance for millions of years, until it no can longer fuse hydrogen nuclei.
  5. After all available hydrogen has been fused, gravity contracts a star raising temperature until other nuclei can fuse.

Keywords

  • Main sequence star - a star which is fusing hydrogen in its core; these stars are stable for long periods of time

  • Red giant star - a larger, cooler, star formed after hydrogen in the core has been depleted

  • White dwarf star - the white hot core of a star after its outer layers have escaped into space

  • Supernova - an exploding star, caused by a gravitational collapse after the fuel is exhausted

  • Neutron star - an incredibly dense star, formed after a supernova

Common misconception

Stars just exist and do not change over time.

Explain the cause and effect of changes in stars and support pupils in explaining these ideas in their own words.

The Orion constellation, which is often clearly visible in the night sky between December and April contains a wide range of star types that can be seen clearly with a telescope or binoculars, including a nebula (below the belt) and a red supergiant star (top left).
Teacher tip

Licence

This content is © Oak National Academy Limited (2024), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).

Lesson video

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Starter quiz

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6 Questions

Q1.
What is a star?
a huge ball of very hot gas and plasma that is burning
a huge ball of very hot gas and plasma with a burning core
a ball of very hot gas and plasma with nuclear fission reactions in its core
Correct answer: a ball of very hot gas and plasma with nuclear fusion reactions in its core
Q2.
What happens in a nuclear fusion reaction?
small nuclei combine to form bigger nuclei of the same element
Correct answer: small nuclei combine to form bigger nuclei of a different element
large nuclei split to form smaller nuclei of the same element
large nuclei split to form smaller nuclei of a different element
Q3.
What is a region of space called that contains traces of hydrogen gas and very fine dust?
Correct Answer: nebula, nebulae, nebulea, a nebula
Q4.
What is a protostar?
Correct answer: a huge ball of dense, hot gas
a huge ball of dense, hot burning gas
a huge ball of dense, hot gas with nuclear fission reactions in its core
a huge ball of dense, hot gas with nuclear fusion reactions in its core
Q5.
What type of nuclei (which element) is fused together in nuclear reactions in the core of a new star?
Correct Answer: Hydrogen, hydrogen gas
Q6.
What type of star fuses hydrogen in its core?
Correct answer: a neutron star
Correct answer: a main sequence star
a protostar
a white dwarf star

Exit quiz

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6 Questions

Q1.
What is the main type of nuclear reaction that takes place in the core of a star?
nuclear fission
Correct answer: nuclear fusion
alpha decay
beta decay
Q2.
How long are very large stars main sequence stars for, compared to average-sized stars?
for much longer than average-sized stars
for about the same time as average-sized stars
Correct answer: for much less time than average-sized stars
Q3.
What causes a star to expand into a red giant star?
increased temperature throughout the star from hydrogen fusion
increased temperature in the core of a star from hydrogen fusion
increased temperature throughout the star from helium fusion
Correct answer: increased temperature in the core of a star from helium fusion
Q4.
What type of star forms from the core of a red giant star after its outer layers have been lost?
Correct answer: a white dwarf star
a white giant star
a white main sequence star
a white nebula
Q5.
What happens to the outer layers of a red supergiant star?
its gravitational force is big enough to hold onto its outer layers
its outer layers escape very slowly into space
its outer layers escape fairly rapidly into space
Correct answer: its outer layers are blasted off into space in an explosion
Q6.
What can form from the core of a red supergiant star after its outer layers have been lost in a supernova explosion?
Correct answer: a black hole
Correct answer: a neutron star
a white dwarf star
a white giant star