IGCSE Physics / Stellar evolution
The life cycle of a massive star
Edexcel International GCSE Physics (4PH1), chapter 27: Stellar evolution, specification point 8.10. Free lesson.
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A massive star forms from a nebula and later explodes as a supernova. Its mass determines whether the core left behind becomes a neutron star or a black hole.
How a massive star forms and evolves
A star with much more mass than the Sun begins in the same way as a Sun-like star. Gravity pulls gas and dust together, and the forming star heats up as it collapses. It then becomes a main sequence star, where hydrogen is fused into helium. A massive star uses its fuel faster, so its main sequence stage is shorter.
How a supernova leaves a neutron star or black hole
After the red supergiant stage, the core collapses and the star blows apart in a huge explosion called a supernova. The object left behind depends on the star’s mass. A neutron star is tiny but extremely dense, while a black hole has gravity so strong that nothing, not even light, can escape. A massive star can leave a neutron star, about 20 km across. The most massive stars can leave a black hole.
How the massive-star path compares with the Sun’s path
The two types of star share the same early stages, but their later stages differ. A Sun-like star becomes a red giant, then its outer layers drift away gently and a white dwarf remains. A massive star becomes a red supergiant and ends in a supernova, leaving a neutron star or black hole. Supernovae also make heavier elements and scatter them into space, where they can form new stars and planets. Both begin as a nebula, protostar and main sequence star. The massive star’s main sequence stage is shorter. Sun-like star: red giant, outer layers drift away, white dwarf. Massive star: red…
Why mass, not size, decides the outcome
A star becomes a supernova because it has much more mass than the Sun, not simply because it is large. A red giant can be huge but still lack enough mass to explode as a supernova. Use the phrase “much more mass than the Sun” when describing which stars become supernovae.
How to describe the stages after the main sequence
For a three-mark answer, give the stages in order and state what may remain after the explosion.