Unit 2 - Life cycles of stars Flashcards
Why are stars stable during the main sequence phase?
The forces (inwards and outwards) are balanced. No need to name the two forces.
What is a protostar?
Gas and dust, brought together under gravity but without nuclear fusion taking place. A star before it begins fusion.
At which stage in a large star’s life cycle are the heaviest elements formed?
During a supernova.
What is nuclear fusion?
The joining of two (small) nuclei to form a larger nuclei.
Describe the fusion that takes place in a star’s main sequence.
Hydrogen fuses to form helium.
What are the stages of a small star similar to the size of our sun after the main sequence phase?
It expands into a red giant then contracts into a white dwarf. It cools and finally, when no radiation is emitted anymore, it becomes a black dwarf.
Describe the stages of a large star, much bigger than our sun, after the main sequence phase.
Expands into a red super giant then contracts and rebounds into a supernova. After that a neutron star remains or if it is big enough a black hole is left.
How does a star shine?
Hydrogen fuses to form helium and lots of heat and light energy are released.
Why can’t the lifetime of a star be determined?
The life time is too longThere is not enough data to allow a value to be accurately calculatedIt is very hard to conduct the measurements needed to calculate lifetime.
What are stars made of?
‘Dust and gas’ (stars are mainly hydrogen).
