AST201H1 Study Guide - Midterm Guide: Spiral Galaxy, White Dwarf
DepartmentAstronomy & Astrophysics
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This is Black K ‘s extraordinary work.
If I made any mistakes please inform me, so I can correct it and tell someone else.
Also, some questions I had no ideas how to answer, please tell me if you know
how to do it as soon as possible. I’ll be pretty appreciative.
Thanks for cooperation.
Those questions in green are the ones I’m not sure.
1. Our Milky Way galaxy holds more than 100 billion stars; 100,000 light yr in diameter
2. Our sun is located in the disk about 28,000 light yr from the centre.
3. 1/00 (calculate by I=L/4D²)
4. B stars, because O stars are all dead. (I’m not sure)
5. Visual; it can be seen by telescope.
6. Ionized He is strongest in O stars; neutral He is strongest in B stars; H is strongest in A
stars, ionized metal is …in G stars, neutral metal … in M stars.
7. apparent brightness of that star; distance
8. 1) I=L/4D²
2) D=3.26/p d is in light year, p is in arc seconds.
9. The cooler one
10. Upper right
11. Either O or B stars.
12. M K G F A B O
13. A molecular cloud > a spinning disk of dusk and gas orbiting a protostar > a protostar
surrounded by a disk and a pair of bipolar jets.
14. O stars are least common, G stars are most common.
15. Lower luminosity one, because lifetime=mass / luminosity
16. Main sequence – red giant – horizontal branch – white dwarf
17. It runs out H fist and then He, then C, then O, Ne, Mag, Si, and the last one is Iron.
A high mass star dies in the cataclysmic explosion of a supernova,scattering newly produced
elements into space and leaving a neutron star or a black hole behind. the supernova occurs
after fusion begins to pile up iron in the high mass star's core. because iron fusion cannot
release energy, the core cannot hold off the crush of gravity for long. in the instant that
gravity overcomes degeneracy pressure, the core collapses and the star explodes
18. Almost no change
19. Firstly, after 10 billion years, the core will be helium ash, then core will cool and contract,
but sun will expand. => becomes a red giant => after another 100 million years, the sun will
run out He => the core cool and contract again =>planetary nebular => white dwarf stars
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