Massive Stars and Stellar Whanau

Question 1

Lifetime

Answer 1

t = 10 × 10^9 M / M^3 = 10^10 /M^2

Question 2

High-Mass Stars

Answer 2

Interstellar cloud (light-years across).
* Collapses down to a proto-star.
* Starts from main-sequence, fusing hydrogen to helium by CNO cycle.
* Forms helium core, becomes red giant.
* Blue loop during helium burning.
* CO core, fusion continue to iron-group elements core.
* Star explodes in a core-collapse supernova. If star explodes with
hydrogen on surface – type II supernova. If all hydrogen has been lost
type Ib/c.
* Leaves neutron star or if massive enough a black hole.

Question 3

binary stars

Answer 3

Most stars are in binary star systems – all more massive stars
are in binaries, for stars like our Sun maybe about 40%.
* While we see many stars in binary by different methods (see
last lecture) in “close” binaries the stars can get in each others
way and increase mass-loss or even merge into one star!
* Evidence is that we see strange supernovae have companions
after the explosions have faded. Can only explain relative rates
of supernovae with binaries.
* We also see neutron stars and black holes in X-ray binaries
but… what are they…?

Question 4

Neutron stars are supported by neutron degeneracy pressure.

Answer 4

This is from
quantum mechanics and is essentially because we can’t put two particles in
the same place.

were discovered by Dame Jocelyn Bell Burnell and are formed
in supernovae. If rapidly spinning observed as pulsars. In binaries they can
cause GW events