Astrophysics Flashcards
1
Q
Nebula (2)
A
- Giant cloud of H gas and interstellar dust
- Gravitational collapse (denser & denser clumps)
2
Q
Protostar (5)
A
- Grav collapse –> work done –> Ek & temp increase
- Large core of material
- Grav field attracts matter until pressure & temp high enough for fusion
- 4 protons –> 1 helium-4 nuclei, 2 positrons, 2 neutrinos, 2 gamma photons
- momentum of photons –> radiation pressure
3
Q
Main Sequence (2)
A
- stable: radiation + gas pressure = grav pressure
- H –> He fusion in core
4
Q
Red Giant (< 10M) (4)
A
- fusion stops as H in core runs out
- radiation pressure decreases –> core collapse
- temp increases: shell H burning, core He burning
- outer layers expand and cool
5
Q
Planetary Nebula (3)
A
- He in core runs out –> collapse –> He shell burning –> increase temp
- C-O core nor hot enough to fuse heavier elements –> unstable –> collapse
- outer layers ejected
6
Q
White Dwarf (4)
A
- solid core left behind
- collapses until no further
- very hot, dense remnant of a low mass star
- grav force = Electron Degeneracy Pressure, so no further collapse
7
Q
Black Dwarf (4)
A
- fusion stops, only heavy elements remain
- radiates energy as photons leak away
- cools down
- when surface temp = few kelvin
8
Q
Red Super Giant (3)
A
- brighter than red giant
- same process
- burning forms heavier elements
9
Q
Supernova (6)
A
- iron core forms –> fusion stops –> unstable –> collapse
- immense grav pot energy force Fe protons + electrons –> neutrons
- releases huge energy
- triggers explosive blowing out of outer shell
- outer layers rebound off core –> shockwaves –> supernova
- temp high enough to fuse elements beyond iron
10
Q
Neutron Star (3)
A
- core mass > Chandrasekhar (1.4)
- core intact after explosion
- very small, extremely dense core
11
Q
Black Hole (4)
A
- core mass > 3-4
- pressure so great
- core collapses into singularity
- escape velocity > speed of light
12
Q
Singularity
A
Theoretical point at which matter is compressed to an infinitely small and dense point and the laws of physics as we understand them break down
13
Q
Electron Degeneracy Pressure (3)
A
- the pressure that stops the grav collapse of a low mass star
- core contracts, compression forces electrons into higher energy levels
- rush of electrons creates EDP
14
Q
The larger the energy level transition
A
the longer the wavelength of the photon emitted
15
Q
Value of energy level =
A
energy required to remove atom from that level
