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1P02 ASTRO - INTRO II > Part 2 > Flashcards

Flashcards in Part 2 Deck (103):
1

When was it was first confirmed that separate galaxies existed outside our own Milky Way galaxy?

in the twentieth century.

2

What are the characteristics of elliptical galaxies?

galaxies that have no disk, no spiral arms, and almost no gas, dust, or new stars forming. These galaxies are called

3

What is a similarity between the Large Magellanic Cloud and the Small Magellanic Cloud

both have a significant amount of gas and dust

4

Elliptical galaxies contain mostly what kind of stars?

older stars

5

Spiral galaxies contain a significant number of what kind of stars?

younger stars

6

The distance ladder is used by astronomers to?

build a distance scale that extends from nearby stars to distant galaxies

7

Spiral galaxies typically contain how much gas and dust?

a lot of gas and dust

8

The method of Cepheid variables is used to?

measure the distances to nearby galaxies

9

The method of globular clusters is used to?

measure the distances to galaxies that are more than 100 million light years away.

10

Astronomers deduce that the universe is expanding by analyzing evidence from?

the cosmic microwave background radiation

11

Galaxy A is 2 times as far from us as Galaxy B. The recession speed of Galaxy A is ____ the recession speed of Galaxy B.

2 times as large as

12

The largest elliptical galaxies appear to be the result of?

galaxy collisions

13

Cosmological redshift is a result of?

space between galaxies expanding

14

Astronomers must be careful to avoid selection effects, which result from what?

result from studying un-representative samples

15

A galaxy is 2 million light-years away. The light from the galaxy that you observe now was emitted?

2 million years ago

16

Rich galaxy clusters contain how many galaxies?

more than one thousand galaxies

17

A standard candle is?

an astronomical object with known luminosity

18

In the 1930s, Fritz Zwicky observed that galaxies in the Coma cluster move too fast to be explained by the visible matter in the galaxy cluster. This was the first evidence for?

dark matter

19

The super-massive black hole at the centre of the Milky Way galaxy contains how much of the galaxy’s mass.?

a tiny fraction of 1%

20

The first discovery of a black hole was made by?

Tom Bolton

21

Gravitational lensing is the?

bending of light from very distant galaxies by more nearby galaxies

22

Gravitational lensing is one of the main ways to collect evidence for?

dark matter

23

Gravitational lensing was first proposed by?

Einstein

24

Gravitational lensing was first confirmed by the observations of?

Eddington

25

When was Cosmic background radiation was first observed? By whom?

1964, by Wilson and Penzias

26

Cosmic background radiation provides what?

provides strong evidence for the Big Bang theory

27

The reciprocal of the Hubble constant gives an approximate value for the age of?

the universe

28

The parameter Ω indicates the fate of the universe. If Ω < 1, then the universe will?

continue to expand indefinitely, but the expansion rate is approximately constant

29

The parameter Ω indicates the fate of the universe. If Ω = 1, then the universe will?

continue to expand indefinitely, but the expansion rate approaches zero more and more closely as time passes.

30

The parameter Ω indicates the fate of the universe. If Ω > 1, then the universe will?

expand for a while, but slow down, reverse, and eventually collapse in a “Big Crunch.”

31

Dark energy tends to?

oppose gravity, and therefore tends to cause the universe to expand

32

Which type of galaxy deviates more from an apparent spherical shape?

E5

33

What do Rich galaxy clusters consist of?

more than one thousand galaxies

34

Observations of elliptical galaxies with multiple nuclei is evidence for?

galaxy mergers

35

Radio galaxies are typically certain elliptical galaxies that emit large amounts of?

synchrotron emission and radio waves

36

Is the universe finite or infinite?

This is not currently known

37

How much power does a typical quasar emit?

much more power than an entire galaxy

38

Right after the Big Bang, the universe was?

very hot and dense, and it expanded and gradually cooled

39

The universe became transparent to light when?

when free electrons and free protons combined

40

The cosmic background radiation currently has its peak in what part of the electromagnetic spectrum?

microwave

41

The observed distribution of chemical elements in the early universe (about 75% hydrogen, about 25% helium, and a trace of lithium) is strong evidence for

the Big Bang theory

42

The currently accepted resolution of Olbers’s paradox is that?

the universe is not infinitely old

43

The idea that the universe is expanding was first proposed by whom based on his or her observations?

Edwin Hubble

44

The Higgs boson was first detected when?

by the LHC(large Hadron Collider) in 2012

45

When was helium was first produced in the universe?

in the first few minutes after the Big Bang

46

The universe is approximately isotropic, which means that?

it has approximately the same properties in all directions

47

One of the predictions of Einstein’s theory of general relativity is that light from distant stars should have its path bent by what?

the gravitational effect of matter between us and the source of the light.

48

Data from the WMAP and Planck satellite observatories suggest that the the universe

is flat (overall), has accelerating expansion, and will probably expand forever

49

In the first minute or so after the Big Bang, atomic nuclei could not exist because why?

it was too hot.

50

Currently, the universe appears to be expanding or contracting?

expanding

51

It is estimated that the first stars and galaxies formed about how long after the Big Bang?

100 million years

52

The classification scheme devised by Hubble, using E, S, and so on, is based on the apparent what of a galaxy?

shape

53

With the aid of modern telescopes, the number of galaxies currently visible is in the?

billions

54

Elliptical galaxies contain mostly what kind of stars?

Population II stars and tend to be red

55

Elliptical galaxies typically contain how much gas and dust?

very little gas and dust

56

Spiral galaxies contain mostly what kind of stars?

Population I stars and tend to be blue

57

For galaxies that are not too distant, astronomers use what method to measure their distances from us?

the method of Cepheid variables

58

In 1929, Hubble discovered a relationship between what of a galaxy

its distance from us and its recession speed

59

One of the conclusions drawn from Hubble’s law is what?

the universe is expanding

60

The largest elliptical galaxies appear to be the result of what?

galaxy collisions

61

Cosmological redshift is a result of what?

space between galaxies expanding

62

The distances to the most distant galaxies are determined using what?

Type Ia supernovae

63

The Large Magellanic Cloud and the Small Magellanic Cloud are what galaxies in what group?

are irregular galaxies in the Local Group

64

Collisions between galaxies are how frequent?

much more frequent than collisions between stars

65

Rich galaxy clusters contain how many galaxies?

more than one thousand galaxies

66

A common result of a galaxy collision is

gravitational distortion of one or both of the galaxies

67

A spiral galaxy has a small bright central region, and the intensity of its radiation varies on a time scale of minutes. The galaxy is most likely a?

a Seyfert galaxy

68

The period of the luminosity variation of a quasar provides insight into the quasar’s

size

69

Quasars are unusual because although they appear star-like, unlike stars they emit large amounts of what?

radio waves

70

The Big Bang theory proposes that the universe and its what were created in an explosion?

fundamental particles (but not atoms)

71

According to the Big Bang theory, what formed about 380 thousand years after the Big Bang?

neutral hydrogen atoms

72

The distance of galaxy A from us is three times the distance of galaxy B from us. The recession speed of A is about _____ the recession speed of galaxy B.

three times

73

Observations of elliptical galaxies with multiple nuclei is evidence what?

galaxy mergers

74

The standard explanation for the powerful emission of radio waves from the core of a radio galaxy is that the radio galaxy contains a super giant what at its core?

black hole

75

A typical quasar emits how much power?

much more power than an entire galaxy

76

The universe became transparent to light when?

when free electrons and free protons combined

77

The age of the universe is about how old?

14 billion years.

78

Why might a galaxy such as M31 (Andromeda) have a blueshifted spectrum instead of a redshifted spectrum?

The effect of its local motion is larger than the effect of the expansion of the universe.

79

A head-on collision between two elliptical galaxies is most likely to produce what?

a ring galaxy

80

One of the predictions of Einstein’s theory of general relativity is that light from distant stars should have its path bent by what?

the gravitational effect of matter between us and the source of the light.

81

It is estimated that the first stars and galaxies formed about how long after the Big Bang?

100 million years

82

Explain the classification scheme for galaxies, based on visual appearance

E galaxies - elliptical
S galaxies - Spiral
Irr galaxies - Irregular Galaxies

83

Describe the main properties of E galaxies. What are the sub-categories of E galaxies, and how do they differ?

E galaxies - elliptical galaxies - are round or elliptical and contain no visible gas and dust, and have few or no bright stars.

They are classified with a numerical index from 0 to 7: 0 is round to 7 being more elliptical

84

Describe the main properties of S galaxies.

S galaxies - spiral galaxies - contain a disk and spiral arms. Their halo stars are not visible, but presumably all spiral galaxies have halos. Spirals contain gas and dust and hot, bright O and B stars.

85

What does the presence of short-lived O and B stars alert us to in spiral galaxies?

That star formation is occurring

86

What are the sub-categories of E galaxies, and how do they differ?

Sa - larger nuclei, less gas and dust, and fewer hot, bright stars
S0 - Have an obvious disk and central bulge but no visible gas or dust and few or no hot bright stars
Sb - Are intermediate
Sc - have a small nuclei, lots of gas and dust, and may hot bright stars

87

What is a characteristic of roughly two-thirds of spiral galaxies?

They are barred - classified as Sba, SBb, and SBc - with an elongated nucleus and spiral arms springing from the ends of the bar.

88

Describe the main properties of Irr Galaxies

They are a chaotic mix of gas and dust and stars with no obvious central bulge or spiral arms. They appear has hazy patches. Star formation is dramatic in their Magellanic clouds, with newborn O and B stars.

89

What is the maximum distance that can be determined with Cepheid variables?

Up to 100 million ly

90

What was Slipher's role in the discovery of Hubble's law?

Vesto Slipher measured wavelengths in the spectra of galaxies and assumed that the shilfts results from the doppler effect. Hubble used Slipher's data on regression velocities galaxies.

91

How does the expansion of the universe result in a cosmological redshift in the spectra of the galaxies?

he stretching of space causes the stretching of the wave - an increase in wavelength - the redshift. The spectra of galaxies are redshifted by the cosmological redshift

92

How are galaxies distributed in the universe?

in clusters:
Rich galaxy clusters: contain more than 1000 galaxies
Poor galaxy clusters: contain less than 1000 galaxies

93

What reasoning supports the use of Type Ia supernova in determining the distance to distant galaxies?

They are very bright and can be observed from great distances. Their luminosity is always the same because they go off when the mass of white dwarf in a binary system hit the Chandrasekhar limit.

94

How likely are collisions between galaxies? How does this compare with the likelihood of collisions between individual stars?

Galaxy collisions are likely and dominate their evolution. Collisions between stars is far less likely because they are much much smaller and farther apart

95

How likely are collisions between galaxies? How does this compare with the likelihood of collisions between individual stars?

Galaxy collisions are likely and dominate their evolution. Collisions between stars is far less likely because they are much much smaller and farther apart

96

What are some of the consequences of galaxy collisions or other interactions between galaxies?

- Galaxies can strip away gas and dust from another galaxy
- Gravitational distortions can occur
- Gas compression
- Galactic mergers
- Creation of spiral arms

97

How are galaxy clusters organized into larger structures in the universe?

They form even bigger super clusters. Super clusters are separated by filaments.

98

What are active galaxies?

Galaxies that emit a large amount of energy via radiation from the small volume in their nuclei

99

What is an active galactic nucleus?

A compact core at the centre of a galaxy that has a much higher luminosity

100

How does a radio galaxy emit such an enormous intensity of radio waves?

With Radio lobes

101

What is a quasar?

Stars which are also intense sources of radio waves

102

What is Olbers's paradox? What is it's signifigance?

1826 - If the universe had existed for ever, is infinite, and uniformly filled with stars, then the night sky should not be dark.

It is plausible to say then that the universe is not infinitely old and the light from the distant stars didn't have time to reach us yet.

103

What is the meaning of (omega) parameter? How is its value related to the overall curvature of spacetime?

It reflects the density/matter relationship.

Omega > 1 - universe is re-collapsing - ends in big crunch.
Omega < 1 - coasting universe - keeps expanding
Omega = 1 - critical universe - keeps expanding but will reduce to zero in infinite future.