8.1.7

Life Cycle of a Star

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Life Cycle of a Star like the Sun

Every star has a life cycle that depends on its size. All stars begin their life cycle in the same way as the Sun. Gravity pulls nebulae (more than 1 nebula) together to form a protostar. This protostar then becomes a main sequence star. If a star is about the same size as the Sun, a star’s lifecycle is like this:

Illustrative background for Main sequenceIllustrative background for Main sequence ?? "content

Main sequence

  • In a main sequence star, hydrogen nuclei are fused together to form helium.
  • This releases energy as heat and light.
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Red giant

  • Eventually all the hydrogen fuel runs out.
  • The star then cools and expands, becoming a red giant.
  • The star then starts to fuse together helium nuclei to release energy.
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White dwarf

  • As the helium fuel runs out, the outward forces reduce in size and the star collapses inwards.
  • This causes its temperature to increase.
  • A white dwarf is formed, which is the hot core of the star.
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Black dwarf

  • When the star completely cools, the star becomes a black dwarf.
  • A black dwarf doesn’t emit (send out) any light or heat.

Life Cycle of a Star Much Bigger than the Sun

A star's life cycle depends on its size. All stars begin their life cycle like the Sun. Gravity pulls nebulae (more than 1 nebula) together to form a protostar, which becomes a main sequence star. If a star is much bigger than the Sun, its life cycle looks like this:

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Red supergiant

  • Nuclear fusion changes more and more of the star’s mass into energy.
  • The star expands into a red supergiant.
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Supernova

  • The largest stars explode in a supernova.
  • A supernova produces elements heavier than iron and scatters them throughout the universe.
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Black hole or neutron star

  • The supernova leaves behind either a black hole or a neutron star.

Jump to other topics

1Energy

2Electricity

3Particle Model of Matter

4Atoms & Radiation

5Forces

5.1Basics of Motion

5.2Forces

5.3Effects of Forces

5.4Pressure

6Waves

7Magnetism

8Astrophysics

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