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Astronomy > Final Exam > Flashcards

Final Exam Flashcards

1
Q

What is spacetime?

A

Four-dimensional combination of space and time that forms the “fabric” of the universe.

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2
Q

What are three possible geometries of spacetime?

A

1) flat geometry
2) spherical geometry
3) saddle-shaped

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3
Q

What is a Doppler shift?

A

Shift in the wavelength of an object’s light caused by its motion toward/away from us

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4
Q

What do we learn from a redshift or blueshift?

A

Tells us how fast the object is moving away from us or towards us.

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5
Q

How does a star’s rotation affect it’s spectral lines?

A

Faster rotating stars have broader spectral lines

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6
Q

How do we measure the age of a star cluster?

A

By finding the main sequence turnoff point on an H-R diagram of stars

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7
Q

What happens when a star can no longer fuse hydrogen to helium in its core?

A

Core shrinks and heats up

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8
Q

What happens as a star’s inert helium core starts to shrink?

A

Hydrogen fuses in shell around core

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9
Q

What are the life stages of a low-mass star?

A

Spends most of its life generating energy by fusing hydrogen in the core, then becomes a red giant with a hydrogen shell burning around an inert helium core

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10
Q

How does a low-mass star die?

A

Expels it’s outer layers into space as a planetary nebula, leaving behind a white dwarf

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11
Q

What are the life stages of a high-mass star?

A

Begins hydrogen shell burning, goes through series of stages burning heavier elements.

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12
Q

How do high-mass stars makes the elements necessary for life?

A

Becomes not enough to fuse with carbon and other elements. The variety of fusion reactions produces different elements that are released when the star dies.

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13
Q

How does a high-mass star die?

A

Explosion of a supernova, scattering newly produced elements into space and leaving a neutron start or black hole behind.

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14
Q

How does a star’s mass determine its life story?

A

Star’s mass determines how it lives life.

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15
Q

How are the lives of stars with close companions different?

A

Stars in a close binary system can transfer mass to their companions.

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16
Q

What happens to a white dwarf when it accretes enough matter to reach the 1.4 Msun limit?

A

It explodes

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17
Q

What is a white dwarf?

A

Core left from a low-mass star supported against the crush of gravity by electron degeneracy pressure

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18
Q

What can happen to a white dwarf in a close binary system?

A

Can acquire hydrogen from its companion through an accretion disk. As it builds hydrogen, it may ignite with nuclear fusion to make a nova.

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19
Q

Could there be neutron stars that appear as pulsars to other civilizations but not us?

A

Yes

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20
Q

How were neutron stars discovered?

A

Neutron stars spin rapidly and their magnetic fields can direct beams of radiation through space as they spin. We see them as pulsars.

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21
Q

How does the radius of the event horizon change when you add mass to a black hole?

A

Increases

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22
Q

What is a black hole?

A

A place where gravity crushed matter into oblivion, creating a hole that nothing can escape.

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23
Q

What is a neutron star?

A

A ball of neutrons created by the collapse of the iron core in a massive star supernova.

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24
Q

What is a pulsar?

A

Rotating neutron stars with magnetic fields.

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25
Q

What property of a black hole determines its size?

A

The mass. Mass determines the event horizon of the black hole.

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26
Q

What observational evidence is there for black holes?

A

We can infer their presence based on their surroundings.

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27
Q

What type of celestial object did Edwin Hubble observe to measure the distance to M31?

A

Cepheid variable stars

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28
Q

What evidence tells is that other galaxies contain dark matter?

A

Their rotational speeds do not steadily decrease with distance from their centres.

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29
Q

What is the evidence for dark matter in galaxies?

A

The orbital velocities if stars and gas clouds in galaxies don’t change much with distance from the galaxy centre. Applying Newton’s laws of gravitation leads to the conclusion that the total mass of a galaxy is get lather then the mass of its stars.

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30
Q

What do we assume when we use a “standard bulb” to find distance?

A

We know the luminosity of the “standard bulb” and light intensity is inversely proportional to distance squared.

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31
Q

Rotational velocity of a spiral galaxy is related to what characteristic?

A

Intrinsic luminosity

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32
Q

Hubble’s law describes what type of relationship?

A

Velocity-distance

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33
Q

What data on a galaxy is necessary to use Hubble’s law as a distance indicator?

A

Redshift in the galaxy’s spectrum

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34
Q

What does the value of Hubble Constant tell us?

A

The rate at which the universe is expanding?

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35
Q

How is the Hubble constant related to the age of the universe?

A

The age of the universe is the inverse of the Hubble constant

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36
Q

What effect does gravity have on the expansion rate of the universe?

A

Gravity tends to decrease the rate of expansion

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37
Q

What evidence suggests that the universe’s rate of expansion is increasing?

A

Distant type la supernova explosions are dimmer than expected.

38
Q

What is the age of the universe, roughly?

A

14 billion years

39
Q

What is the fate of the universe, based on the rate of expansion and changes in the rate of expansion?

A

The universe will expand forever at an increasing rate

40
Q

How does the temperature and density of the early universe compare to these same conditions today?

A

The early universe was hotter and denser.

41
Q

How do the abundances of elements support the Big Bang?

A

Big Bang predicts that the chemical composition of the universe should be about 75% hydrogen and 25% helium, which is correct

42
Q

What aspects of the universe were originally unexplained by the Big Bang?

A

1) the origin of the density enhancements that turned into galaxies and larger structures
2) the overall smoothness of the universe on large scales
3) the fact that the actual density of matter is close to critical density

43
Q

How can we test the idea of inflation?

A

Models of inflation make specific predictions about the temperature patterns we should observe in the cosmic microwave background. The observed patterns recently match these

44
Q

What does the Milky Way look like?

A

Halo surrounds galaxy, disk contains gas and dust, disk is 100,00 light years in diameter

45
Q

Where do stars tend to form in our galaxy?

A

Spiral arms - due to gas clouds crashing into each other

46
Q

What lies in the centre of our galaxy?

A

A large black hole about 3 to 4 million times as massive as the sun

47
Q

What is Hubble’s law?

A

More distant galaxies are moving away faster. This allows us to determine a galaxy’s distance from the speed at which it is moving away from us.

48
Q

How do distance measurements tell us the age of universe?

A

Combining distance measurements with velocity measurements tells us Hubble’s constants and tells us the inverse of that.

49
Q

What do we mean by dark matter and dark energy?

A

Dark matter is the unseen mass whose gravity governs the observed motions of stars and gas clouds.
Dark energy is the name given to whatever may be causing expansion of the universe to accelerate.

50
Q

What is the evidence for dark matter in clusters of galaxies?

A

Different methods - gravitational lensing, galaxy orbits. All agree that the mass of a cluster is about 50x the mass of its stars, implying dark matter.

51
Q

Is the expansion if the universe accelerating and what proofs this?

A

Observations of distant supernova indicate this.

52
Q

What were conditions like in the early universe?

A

Filled with radiation and elementary particles, extremely hot and dense.

53
Q

What is the history of the universe according to the Big Bang Theory?

A 
Era of Galaxies
Era of Atoms
Era of Nucleosynthesis
Particle Era
Electroweak Era
GUT Era
Planck Era
54
Q

How former observe the radiation left over from the Big Bang?

A

Telescopes that can detect microwaves allow us to observe this

55
Q

Where did the solar system come from?

A

A cloud of gas that was the result of gas recycling

56
Q

What is the basic idea behind the nebular theory?

A

Our solar system formed from a giant, swirling cloud of gas and dust.

57
Q

What was the solar nebula?

A

The piece of interstellar cloud from which the Solar System was born

58
Q

How did gravitational collapse affect the Solar nebula?

A

Nebula heated up, spun faster and flattened into a disk

59
Q

What produced the orderly motion we observe in the solar system today?

A

Planets retain the motion of the spinning disk of the solar nebula

60
Q

What key fact explains why there are two types of planet?

A

Differences in condensation at different distances from the Sun

61
Q

Describe basic steps by which the terrestrial planets formed.

A

Condensation of solid grains of metal and rock, accretion into planetesimals, growth of planetesimals into planets

62
Q

Describe the basic steps by which the Jovian planets formed.

A

Condensation of metal, rock, and ice. Accretion into icy planetesimals, making “miniature solar nebulae” Jovian planets form at nebula centres while moons accrete from ice in the spinning disks.

63
Q

What is origin of asteroids and comets?

A

Asteroids are leftover planetesimals of the inner solar system, and comets are leftovers from the outer solar system

64
Q

What was the heavy bombardment?

A

The period where planets were bombarded by many leftover planetesimals

65
Q

How do we think that our Moon formed?

A

A leftover planetesimal slammed into Earth, blasting rock from Earth’s outer layers into orbit, where it re-accreted to form the Moon

66
Q

How do we measure the age of a rock?

A

Radiometric dating gives the time since a rock lady solidified.

67
Q

How old is the Solar System and how do we know?

A

4.6 billion years, determined from radiometric dating

68
Q

Briefly describe the Jovian planets

A

Largely composed of hydrogen, helium and hydrogen compounds. No solid surfaces. Fast rotation. Many moons. Squished shapes. Ring systems.

69
Q

Rank the planet sizes

A

Pluto, Mercury, Mars, Venus, Earth, Neptune, Uranus, Saturn, Jupiter

70
Q

Is the temperature on Mercury higher than on Earth?

A

On the daytime side, yes, but the nighttime side is very cold fur to Mercury having little atmosphere to retain heat

71
Q

What is the composition of the clouds surrounding Venus?

A

Primarily sulphuric acid

72
Q

Does Mars have surface water today?

A

No, but it seems it may have had liquid water in the past.

73
Q

Is life known to exist on Mars today?

A

No

74
Q

What are the major patterns of motion in our solar system?

A

Orbit in the same direction and same plane.

75
Q

Where do we find asteroids and comets in the solar system?

A

Most asteroids reside in the asteroid belt between Mars and Jupiter. Comets are found in the Kuiper belt and the Oort Cloud.

76
Q

The age of our solar system is

A

4.6 billion years

77
Q

What are the two types of planets?

A

Jovian and Terrestrial

78
Q

What do we call a small piece of solar system found on earth?

A

Meteorite

79
Q

What planets are Jovian planets?

A

Jupiter, Saturn, Uranus and Neptune

80
Q

What property of planets can be obtained from the study of orbits of moons and the law of gravity?

A

Mass

81
Q

What two planets have no moon?

A

Mercury and Venus

82
Q

What property of Jovian planets is less than that of terrestrial planets?

A

Density

83
Q

Which two planets have nearly the same chemical makeup as the Sun?

A

Jupiter and Saturn

84
Q

What is an untrue fact about asteroids?

A

They are icy bodies

85
Q

Could there be life on Europa or other Jovian moons?

A

Possibly

86
Q

Which method has been most successful in locating planets orbiting other stars?

A

The planet transit method

87
Q

What are the necessities of life?

A

Nutrients, liquid water, and energy

88
Q

What body in the outer solar system had the greatest possibility of harbouring life?

A

Europa

89
Q

Which band of the electromagnetic spectrum turns out to be the best for sending messages to other stars?

A

Radio

90
Q

What is the primary topic of the general theory of relativity?

A

The force of gravity arises from distortions of spacetime

Astronomy (4 decks)

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