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Final Flashcards

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1
Q

What are white dwarfs?

A

Remaining cores of dead, low mass stars

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2
Q

What supports white dwarfs against gravity?

A

electron degeneracy pressure

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3
Q

White dwarf’s with the same mass as the Sun are about the same size as what planet?

A

Earth

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4
Q

What is the typical density of a white dwarf?

A

10^6 gram/cubic cm

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5
Q

Lower/higher mass white dwarfs are smaller

A

higher

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6
Q

White dwarfs cannot be more massive than 1.4 MSun because of the…

A

Chandrasekhar limit

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7
Q

For white dwarfs in close binaries, mass falls toward them from…

A

binary companion

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8
Q

For white dwarf in close binaries, gas orbits them in an…

A

accretion disk

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9
Q

For white dwarfs in close binaries, friction causes what to them?

A

heating and accretion

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10
Q

Fusion begins suddenly and explosively, causing a…

A

nova explosion

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11
Q

What are the 2 kinds of supernovas?

A

type 1= explosion of white dwarf in binary (no H)
type 2= death explosion of massive star (H)

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12
Q

What is a neutron star?

A

A ball of neutrons left behind by a massive-star supernova

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13
Q

What are pulsars?

A

Radiation beams along a magnetic axis that is not aligned with the rotation axis

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14
Q

The pulsar at the center of Crab Nebula pulses how many times per second?

A

30 times

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15
Q

What forms x-ray binaries?

A

hot gas in the accretion disk forms X-rays

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16
Q

What is a black hole?

A

An object whose gravity is so powerful that not even light can escape it

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17
Q

What is the event horizon?

A

the “surface” of a black hole where the radius at which the escape velocity equals the speed of light

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18
Q

Nothing can escape from within the event horizon because…

A

nothing can go faster than light

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19
Q

What is the Schwarzschild radius?

A

The radius of the event horizon

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20
Q

What would happen to Earth if the Sun suddenly became a black hole?

A

Earth would continue to orbit the now invisible Sun

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21
Q

What was the first direct evidence of a black hole?

A

Cygnus X-1

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22
Q

What are the 2 models for gamma-ray bursts?

A

merging neutron stars & a hypernova

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23
Q

What is a hypernova?

A

An explosion of a very massive star that leads to the birth of a black hole

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24
Q

Energy lost in gravity waves causes stars to spiral…

A

inward

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25
What do the Laser Interferometer Gravitational-wave Observatories (LIGO) do?
They work together to detect the gravitational waves of 2 black holes colliding
26
M<0.08 MSun
Star cools as brown dwarf
27
0.08
white dwarf remnant
28
10
neutron star remnant
29
18
black hole remnant
30
M>140MSun
no remnant?
31
Barred spiral galaxy
Has a bar of stars across the bulge. Stars have very elongated orbits passing near center
32
Elliptical galaxy
All spheroidal components, virtually no disk component. Stars orbit in all directions
33
Lenticular galaxy
Has a disk like a spiral galaxy but much less dusty gas (intermediate between spiral and elliptical)
34
Standard candle
An object whose luminosity is known
35
Hubble's Law
All galaxies seem to be moving away from us: the greater the distance, the higher the redshift
36
What is the current value for Hubble's constant
H0= 72 km/sec/megaparsec (1 megaparsec=10^6 parsec)
37
Cosmological principle
The universe looks about the same everywhere
38
What is the age of the universe from Hubble's constant?
13.4 billion years
39
What forms protogalactic clouds?
denser regions contracting
40
What gases in protogalactic clouds formed the first stars?
H and He
41
Initial angular momentum of protogalactic cloud could determine size of resulting disk
Spin
42
Elliptical galaxies could come from dense protogalactic clouds that were able to cool and form stars before gas settled into a disk
Density
43
What was common in early, smaller universe?
collisions
44
2 spiral galaxies can merge to make...
an elliptical
45
What galaxies form stars so quickly they would use up all their gas in less than a billion years?
starburst galaxies
46
The intensity of supernova explosions in starburst galaxies can drive...
galactic winds
47
What do we call the center of a galaxy that is unusually bright?
active galactic nucleus
48
-Luminosity can be enormous (> 10^12 LSun) -Luminosity can rapidly vary -Emit energy over a wide range of wavelengths -Some drive jets of plasma at near light speed -Driven by a SMBH
Characteristics of active galaxies
49
What galaxies contain active nuclei shooting out vast jets of plasma that emit _ waves coming from electrons moving at near-light speed?
radio galaxies, radio
50
Why don't radio galaxies appear as quasars?
dusty gas clouds block our view of accretion disk
51
What does accretion of gas onto a supermassive black hole (SMBH) produce?
friction, heat, radiation, jets
52
What between a quasar and earth absorb some of a quasar's light?
gas clouds
53
Mass of a galaxy's central black hole is closely related to...
the mass of its bulge
54
-Collisions of galaxies and gas infall -Explosions of clusters of massive stars -Concentrating stars in the center of star clusters -Very dense locations
How SMBH form
55
The early universe was both...
dense and hot
56
As the universe cooled, it went from being radiation-dominated to being...
matter-dominated
57
New particles formed by collisions of...
photons
58
Pair production and annihilation process started in...
equilibrium
59
Holds nuclei together exchange particle: gluons
strong force
60
Holds electrons in atoms exchange particle: photons
electromagnetic force
61
Mediates nuclear reactions exchange particle: weak bosons
weak force
62
Holds large-scale structures together exchange particles: gravitons
gravity
63
At what temperature do forces become similar (unify)?
higher temperatures
64
Fundamental particles are based on...
mass, charge, spin
65
What are protons and neutrons made of?
quarks
66
In what era did galaxies form at age ~ 1B years
era of galaxies
67
In what era did atoms form at age ~ 380,000 years?
era of atoms
68
In what era was most of He made by 3 minutes?
era of nuclei
69
In what era did protons, neutrons begin to fuse (H, He) but larger nuclei were broken by collisions?
era of nucleo-synthesis
70
In what era were the amounts of matter and antimatter nearly equal?
particle era
71
What era lasts until electroweak force separates into weak and electromagnetic forces?
electroweak era
72
In what era are strong and weak nuclear forces and electromagnetism all unified?
GUT era
73
1. Expansion of the Universe (Hubble's Law) 2. Detection of the radiation from the Big Bang 3. Abundances of helium and light elements 4. Structure in the Universe
Observational Cosmology: Primary Evidence
74
The radiation left over from the Big Bang
cosmic microwave background
75
Overall geometry of the universe is closely related to total...
density of matter and energy
76
Where does the visible portion of a galaxy lie?
deep in the heart of a large halo of dark matter
77
what do all spiral galaxies tend to have?
flat rotation curves
78
How much larger is the mass from galaxy motions in a cluster than the mass in stars?
50x larger
79
Dark matter in galaxy clusters contain large amounts of?
x-ray emitting hot gas
80
What is the bending of light rays by gravity that can also tell us a cluster's mass?
gravitational lensing
81
Weakly interacting massive particles (WIMPS) can't contract because...
they don't radiate away their energy
82
Maps of galaxy positions reveal extremely large structures:
superclusters and voids
83
What is responsible for the structure in the universe?
dark matter
84
An undetected form of mass that emits little or no light but whose existence we infer from its gravitational influence
dark matter
85
An unknown form of energy that seems to be the source of repulsive force causing the expansion of the universe to accelerate
dark energy
86
-Direct imaging -Stellar wobbles and Doppler shifts -Planetary transits
How we can detect planets around other stars
87
What is the habitable zone?
temperature for liquid water
88
What is the first known earth-planet to lie within the habitable zone of a star beyond the sun?
Planet Kepler-186f
89
What is the star formation rate in our galaxy?
5-10 per year on average
90
What is the Drake equation for the number of technical civilizations currently in the milky way?
N = (SFR) x nhabit planets x flife x fintel x ftech x L

Astronomy (3 decks)

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