1.
How do stars form?
Stars are born in cold, relatively dense
molecular clouds. As a cloud fragment collapses under gravity, it becomes a
protostar surrounded by a spinning disk of gas. The protostar may also fire
jets of matter outward along its poles.
2.
How massive are newborn stars?
Stars greater than about 150MSun
would be so luminous that radiation pressure would blow them apart. Degeneracy
pressure stops the contraction of objects <0.08MSun before
fusion starts.
3.
What are the life stages of a low-mass star?
H fusion in core (main sequence) H fusion
in shell around contracting core (red giant) He fusion in core (horizontal
branch) Double shell-burning (red giant)
4.
How does a low-mass star die?
Ejection of H and He in a planetary nebula
leaves behind an inert white dwarf.
5.
What are the life stages of a high-mass star?
They are similar to the life stages of a
low-mass star.
6.
How do high-mass stars make the elements
necessary for life?
Higher masses produce higher core
temperatures that enable fusion of heavier elements.
7.
How does a high-mass star die?
The iron core collapses, leading to a
supernova.
8.
How does a star’s mass determine its life story?
Mass determines how high a star’s core
temperature can rise and therefore determines how quickly a star uses its fuel
and what kinds of elements it can make.
9.
How are the lives of stars with close companions
different?
Stars with close companions can exchange
mass, altering the usual life stories of stars.
10. Choose a supernova from Wikipedia, and
describe it.
A Thermal Runaway, which is a white dwarf
star. It may accumulate from a
stellar companion. To help raise the core temperature to ignite carbon fusion
at which point it undergoes runaway nuclear fusion, completely disrupting it.
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