Stellar EvolutionEdexcel IGCSE Physics: Flashcards

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What determines a star's colour?

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What determines a star's colour?: Its surface temperature.
Which colour stars are hottest?: Blue and white stars.
Which colour stars are coolest?: Red stars.
Give the life cycle stages of a Sun-like star.: Nebula → main sequence star → red giant → white dwarf.
What is a nebula?: A cloud of dust and gas in space that can contract under gravity to form a new star.
What happens during the main sequence stage of a star's life?: The star fuses hydrogen into helium in its core, releasing energy, for a stable long period.
What is a red giant?: A large, cool, reddish star formed when a main sequence star runs low on hydrogen fuel and expands.
What is a white dwarf?: A small, extremely dense, hot core left behind after a red giant sheds its outer layers.
Give the life cycle stages of a star much more massive than the Sun.: Nebula → main sequence star → red supergiant → supernova → neutron star or black hole.
What is a supernova?: A massive, explosive collapse and explosion at the end of a very massive star's life.
What determines whether a supernova remnant becomes a neutron star or a black hole?: The mass remaining after the supernova — very high remaining mass forms a black hole; lower remaining mass forms a neutron star.
Define absolute magnitude.: A measure of a star's true brightness as it would appear if viewed from a standard distance.
What is plotted on the two axes of the Hertzsprung–Russell diagram?: Temperature (horizontal axis) against luminosity/absolute magnitude (vertical axis).
Where do main sequence stars appear on the HR diagram?: In a diagonal band running from hot/bright (top left) to cool/dim (bottom right).
Where do white dwarfs appear on the HR diagram?: Towards the bottom left — hot but dim because they are small.