Unit 2 - Life cycles of stars Flashcards
(10 cards)
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).
