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Astronomy > Final > Flashcards

Final Flashcards

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
Q

What do the Laser Interferometer Gravitational-wave Observatories (LIGO) do?

A

They work together to detect the gravitational waves of 2 black holes colliding

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26
Q

M<0.08 MSun

A

Star cools as brown dwarf

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27
Q

0.08<M<10MSun

A

white dwarf remnant

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28
Q

10<M<18MSun

A

neutron star remnant

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29
Q

18<M<140MSun

A

black hole remnant

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30
Q

M>140MSun

A

no remnant?

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31
Q

Barred spiral galaxy

A

Has a bar of stars across the bulge. Stars have very elongated orbits passing near center

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32
Q

Elliptical galaxy

A

All spheroidal components, virtually no disk component. Stars orbit in all directions

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33
Q

Lenticular galaxy

A

Has a disk like a spiral galaxy but much less dusty gas (intermediate between spiral and elliptical)

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34
Q

Standard candle

A

An object whose luminosity is known

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35
Q

Hubble’s Law

A

All galaxies seem to be moving away from us: the greater the distance, the higher the redshift

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36
Q

What is the current value for Hubble’s constant

A

H0= 72 km/sec/megaparsec (1 megaparsec=10^6 parsec)

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37
Q

Cosmological principle

A

The universe looks about the same everywhere

38
Q

What is the age of the universe from Hubble’s constant?

A

13.4 billion years

39
Q

What forms protogalactic clouds?

A

denser regions contracting

40
Q

What gases in protogalactic clouds formed the first stars?

A

H and He

41
Q

Initial angular momentum of protogalactic cloud could determine size of resulting disk

A

Spin

42
Q

Elliptical galaxies could come from dense protogalactic clouds that were able to cool and form stars before gas settled into a disk

A

Density

43
Q

What was common in early, smaller universe?

A

collisions

44
Q

2 spiral galaxies can merge to make…

A

an elliptical

45
Q

What galaxies form stars so quickly they would use up all their gas in less than a billion years?

A

starburst galaxies

46
Q

The intensity of supernova explosions in starburst galaxies can drive…

A

galactic winds

47
Q

What do we call the center of a galaxy that is unusually bright?

A

active galactic nucleus

48
Q

-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

A

Characteristics of active galaxies

49
Q

What galaxies contain active nuclei shooting out vast jets of plasma that emit _ waves coming from electrons moving at near-light speed?

A

radio galaxies, radio

50
Q

Why don’t radio galaxies appear as quasars?

A

dusty gas clouds block our view of accretion disk

51
Q

What does accretion of gas onto a supermassive black hole (SMBH) produce?

A

friction, heat, radiation, jets

52
Q

What between a quasar and earth absorb some of a quasar’s light?

A

gas clouds

53
Q

Mass of a galaxy’s central black hole is closely related to…

A

the mass of its bulge

54
Q

-Collisions of galaxies and gas infall
-Explosions of clusters of massive stars
-Concentrating stars in the center of star clusters
-Very dense locations

A

How SMBH form

55
Q

The early universe was both…

A

dense and hot

56
Q

As the universe cooled, it went from being radiation-dominated to being…

A

matter-dominated

57
Q

New particles formed by collisions of…

A

photons

58
Q

Pair production and annihilation process started in…

A

equilibrium

59
Q

Holds nuclei together
exchange particle: gluons

A

strong force

60
Q

Holds electrons in atoms
exchange particle: photons

A

electromagnetic force

61
Q

Mediates nuclear reactions
exchange particle: weak bosons

A

weak force

62
Q

Holds large-scale structures together
exchange particles: gravitons

A

gravity

63
Q

At what temperature do forces become similar (unify)?

A

higher temperatures

64
Q

Fundamental particles are based on…

A

mass, charge, spin

65
Q

What are protons and neutrons made of?

A

quarks

66
Q

In what era did galaxies form at age ~ 1B years

A

era of galaxies

67
Q

In what era did atoms form at age ~ 380,000 years?

A

era of atoms

68
Q

In what era was most of He made by 3 minutes?

A

era of nuclei

69
Q

In what era did protons, neutrons begin to fuse (H, He) but larger nuclei were broken by collisions?

A

era of nucleo-synthesis

70
Q

In what era were the amounts of matter and antimatter nearly equal?

A

particle era

71
Q

What era lasts until electroweak force separates into weak and electromagnetic forces?

A

electroweak era

72
Q

In what era are strong and weak nuclear forces and electromagnetism all unified?

A

GUT era

73
Q
  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
A

Observational Cosmology: Primary Evidence

74
Q

The radiation left over from the Big Bang

A

cosmic microwave background

75
Q

Overall geometry of the universe is closely related to total…

A

density of matter and energy

76
Q

Where does the visible portion of a galaxy lie?

A

deep in the heart of a large halo of dark matter

77
Q

what do all spiral galaxies tend to have?

A

flat rotation curves

78
Q

How much larger is the mass from galaxy motions in a cluster than the mass in stars?

A

50x larger

79
Q

Dark matter in galaxy clusters contain large amounts of?

A

x-ray emitting hot gas

80
Q

What is the bending of light rays by gravity that can also tell us a cluster’s mass?

A

gravitational lensing

81
Q

Weakly interacting massive particles (WIMPS) can’t contract because…

A

they don’t radiate away their energy

82
Q

Maps of galaxy positions reveal extremely large structures:

A

superclusters and voids

83
Q

What is responsible for the structure in the universe?

A

dark matter

84
Q

An undetected form of mass that emits little or no light but whose existence we infer from its gravitational influence

A

dark matter

85
Q

An unknown form of energy that seems to be the source of repulsive force causing the expansion of the universe to accelerate

A

dark energy

86
Q

-Direct imaging
-Stellar wobbles and Doppler shifts
-Planetary transits

A

How we can detect planets around other stars

87
Q

What is the habitable zone?

A

temperature for liquid water

88
Q

What is the first known earth-planet to lie within the habitable zone of a star beyond the sun?

A

Planet Kepler-186f

89
Q

What is the star formation rate in our galaxy?

A

5-10 per year on average

90
Q

What is the Drake equation for the number of technical civilizations currently in the milky way?

A

N = (SFR) x nhabit planets x flife x fintel x ftech x L

Astronomy (2 decks)

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