Lecture 24 Flashcards
1
Q
How do the heavy (heavier than iron) form?
A
- since elements heavier than iron do not generate energy through fusion, adding energy is the only way to fuse them (endothermic reaction)
- all elements up to uranium can be fused due to the large amount of energy created by a supernova
2
Q
Why are there more elements with even numbers of atomic elements?
A
Helium capture
3
Q
Why are elements heavier than iron rare?
A
These elements are made primarily by brief fusion reactions during a supernova
4
Q
Why do supernovae release many neutrinos?
A
Due to the collapse of iron into neutrons
5
Q
How does metal production and recycling effect the composition of stars?
A
- stars are formed from interstellar gas clouds
- small stars live for a very long time (essentially forever) and do not return elements to the ISM
- massive stars have short lives and return heavy elements to the ISM- many generations of high mass stars increase the galaxy’s metallicity
6
Q
What can the composition of normal stars tell us?
A
They are a snapshot of the abundance patterns typical of when they were formed
7
Q
What is in the stellar graveyard?
A
- white dwarves
- neutron stars
8
Q
Why do neutron stars spin so fast?
A
- the shrinking conserves angular momentum
- collapse increases both rotation and magnetic fields
- older stars spin slower as angular momentum is lost
9
Q
What is a pulsar?
A
A rotating neutron star
10
Q
What are some important features of neutron stars?
A
- approximately 1-3M(sun)
- have a solid crust of crystalline iron
- heavy liquid interior made of neutrons (and some other particles)
- structure is determined by gravity VS neutron degeneracy pressure
