Stellar Evoloution Flashcards
How are stars classified?
Stars are classified according to their colour which is related to their surface temperature.
What does the colour of a star tell us?
The colour indicates the temperature of the star with blue being the hottest and red being the coolest.
What type of light do hotter stars emit?
Hotter stars emit more high frequency light such as blue and violet.
What type of light do cooler stars emit?
Cooler stars emit more low frequency light such as red and orange.
What is the order of star colours from hottest to coolest?
Blue white yellow orange red.
Why do stars appear different colours?
Because their surface temperatures affect the frequency of light they emit.
Which colour stars are the coldest?
Red stars are the coldest type of star.
How does star formation begin?
Star formation begins when a cloud of dust and gas aggregates to form a nebula.
What is a nebula mainly composed of?
A nebula is mainly composed of hydrogen.
What force causes particles in a nebula to come together?
The force of gravity pulls the dust and gas particles together.
What is formed as gravity pulls gas and dust together?
A protostar is formed.
What happens as a protostar’s temperature rises?
Hydrogen nuclei fuse to form helium in a process called nuclear fusion.
What does nuclear fusion release?
Nuclear fusion releases energy.
Why does the core of the star remain hot?
Because energy is released by nuclear fusion keeping the core hot.
What causes a star to enter the stable phase?
The outward pressure from nuclear fusion balances the inward pull of gravity.
How long can a star stay in the stable phase?
Several billion years.
What happens when a star uses up its hydrogen fuel?
Gravity exceeds the pressure from fusion and compresses the star.
Why does the star expand and become red?
Compression from gravity increases temperature which expands the star and cools its surface.
What is a red giant?
A cooler, expanded star formed from a small or medium star like the Sun.
What is a red supergiant?
A cooler, expanded star formed from a larger star.
How does a red giant become a white dwarf?
It ejects its outer layers and the hot dense core remains.
Why is a white dwarf hot and dense?
It is the leftover core of the red giant and has a high surface temperature.
What happens to a red supergiant after it expands?
It continues fusion until it explodes in a supernova.
What are the possible remnants of a supernova?
A neutron star or a black hole.
