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Astronomy > Test 4 > Flashcards

Test 4 Flashcards

0
Q

Why can we see a band of milky white clouds as part of the Milky Way?

A

We’re inside the galaxy’s pancake shape.

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1
Q

The Milky Way is a collection of ___#___ stars in a _____ shape.

A

a few hundred billion stars; pancake

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2
Q

What is the closest spiral galaxy to the Milky Way? How far away is it?

A

Andromeda; 2 million light years

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3
Q

What is the diameter of a typical galaxy?

A

100,000 light years

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4
Q

How many miles is a light year equal to?

A

6 trillion

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5
Q

What did William Hershall do?

A

He was an astronomer who tried to estimate where we are in the galaxy and its size.

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6
Q

How did Hershall attempt to measure the galaxy?

A

Star counts

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7
Q

What was Hershall’s conclusion?

A

The Milky Way isn’t very big and we are in the center.

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8
Q

star counts

A

Count stars to estimate distance

Ex. If a galaxy were to measure 10 stars by 1000 stars, it would extend farther to the right.

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9
Q

What did Harlow Shapley do?

A

He was an astronomer who counted globular clusters (rather than individual stars) to measure the galaxy.

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10
Q

What did Henrietta Levitt do?

A

She was a Harvard computer in the early 20th century. She discovered that cepheid variable stars have a relationship between luminosity and period.

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11
Q

Cepheid variable stars burn ____ in the core.

A

Helium

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12
Q

Define period of a variable star.

A

Time it takes to go bright, faint, then bright again

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13
Q

Luminosity allows us to find ____.

A

Distance

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14
Q

What did Shapley mistakenly study?

A

RR Lyrae Stars

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15
Q

What are the 5 parts of the Milky Way galaxy?

A

Nucleus, dust, gas lanes, disc, halo

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16
Q

Our galaxy used to be ____, but ___ ___ ___ happened.

A

spherical; Pizza Dough Physics

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17
Q

Where in the galaxy is the Sun located?

A

About 2/3 of the way between the center and the edge

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18
Q

How do we know how many stars are in the Milky Way?

A

Measure speed and orbital period.
1- Use Kepler’s Laws
2- Assume Sun is average mass
Formula: Mass of galaxy divided by mass of Sun

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19
Q

The galaxy is ____ massive than we thought.

A

more

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20
Q

Recent evidence suggests the Milky Way is a ____ spiral galaxy.

A

barred

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21
Q

How do we know the Milky Way has a spiral arm structure?

A

using H emitted radio waves, astronomers mapped it out

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22
Q

Which goes through dust easier: optical light or radio waves?

A

Radio waves

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23
Q

Spiral arms emit ____.

A

radio waves

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24
Q

Space between stars is filled with ___.

A

Hydrogen

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25
Q

What is the length of a radio wave emitted by H?

A

21 cm

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26
Q

H atoms in the ___ ___ of the galaxy emit ___ ___.

A

spiral arms; radio waves

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27
Q

Where does the Spiral Density Wave come from?

A

Center of Milky Way

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28
Q

What is the Spiral Density Wave’s pattern?

A

Compressed, spread out, compressed, etc.

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29
Q

What is Sagittarius A?

A

First radio source discovered in Sagittarius constellation

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30
Q

Sagittarius A is very ____.

A

bright

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31
Q

What is Sagittarius B?

A

Second radio source discovered in Sagittarius constellation

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32
Q

What drives the Spiral Density Wave?

A

No one knows

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33
Q

Why do we get radio waves coming from the center of the galaxy?

A

Magnetic field; Synchrotron Radiation

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34
Q

The most energetic source in the core of the Milky Way is the size of a ____ ____.

A

solar system

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35
Q

What do we suspect is spinning at the Milky Way’s core?

A

Super massive black hole

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36
Q

What makes a black hole super massive?

A

Small black holes merge

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37
Q

Who proved there were other galaxies?

A

Edwin Hubble

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38
Q

What is Extra-Galactic Astronomy?

A

Study of astronomy outside of the Milky Way

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39
Q

Edwin Hubble proved that the universe is ____.

A

expanding

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40
Q

Where did Edwin Hubble make his observations?

A

Telescope on Mt. Wilson

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41
Q

Who was Hubble’s assistant?

A

Milton Humison

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42
Q

Who discovered the Andromeda Galaxy? How?

A

Hubble; He found cepheid variable stars and figured out the period, luminosity, and distance. The distance is longer than the Milky Way’s diameter, proving it’s a galaxy outside of ours.

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43
Q

How far away is Andromeda?

A

2 million light years

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44
Q

What is the Milky Way’s approximate diameter?

A

100,000 light years

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45
Q

Hubble classified galaxies based on ____.

A

appearance

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46
Q

What are Hubble’s 2 broad categories for galaxies?

A

Elliptical & Spiral

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47
Q

There are ____ and Giant Elliptical galaxies.

A

dwarf

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48
Q

How many types of Elliptical galaxies are there? How do they vary?

A

8 (E0-E7). E0 is spherical like a basketball. E7 is elongated like a football.

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49
Q

What are the 2 types if spiral galaxies?

A

Normal/Ordinary (S or SA) and Barred (SB)

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50
Q

What is an S0 galaxy?

A

S0 galaxies are an intermediate type of galaxy between E7 and a “true” spiral Sa. They differ from ellipticals because they have a bulge and a thin disk, but are different from Sa because they have no spiral structure. S0 galaxies are also known as Lenticular galaxies.

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51
Q

What are the 3 components of a spiral galaxy?

A

Nucleus, disc, halo

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52
Q

Describe an Sa galaxy.

A

Spirals compressed, tightly wound around nucleus

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53
Q

Describe an S0 galaxy.

A

Disc with no spirals

54
Q

Describe an Sc galaxy.

A

Spirals spread out, loosely wound

55
Q

An Sb galaxy is characteristically between ___ and ___.

A

Sa, Sc

56
Q

Galactic Cannibalism

A

how galaxies accrete mass; merging with other galaxies

57
Q

Hubble’s Classes: Irregulars

A

galaxies that don’t fit any of Hubble’s classes; no shape

58
Q

Hubble’s Classes: pec

A

peculiar; a galaxy that doesn’t perfectly fit a class

59
Q

What are the 6 main properties of galaxies?

A

diameter, mass, luminosity, color, percentage of gas content, types of stars

60
Q

How does a Giant Elliptical galaxy compare to the Milky Way?

A

bigger, brighter, more massive

61
Q

How does a Dwarf Elliptical galaxy compare to the Milky Way?

A

smaller, less massive, fainter

63
Q

What color is a sample of old stars?

A

Red

63
Q

Describe the stars in an Irregular Galaxy.

A

young, blue, high percentage of gas

64
Q

What color is a sample of young stars?

A

blue

65
Q

What type of stars does an Elliptical Galaxy have?

A

old, red

66
Q

What type of stars does a Spiral Galaxy, like the Milky Way, have?

A

mix of old and new, mix of red and blue

67
Q

Elliptical Galaxies tend to be ___ with ___ gas content. They ___(are/ are not)___ forming new stars and appear ___ in color.

A

Elliptical Galaxies tend to be old with very little gas content. They are not forming new stars and appear red in color.

68
Q

A cepheid variable star is a ___ indicator, sometimes called a ___.

A

distance; candle

69
Q

The further away a galaxy is, the ___ it appears to be moving away from us.

A

faster

70
Q

The Sun and similar stars can produce an HNK spectral line from ____.

A

Calcium

71
Q

When did Hubble discover the universe was expanding?

A

1930s

72
Q

What other scientist predicted the universe’s expansion before Hubble? Why isn’t he credited with the discovery?

A

Einstein, Theory of General Relativity in 1915; he didn’t believe it, so he altered the data to disprove expansion, he later admitted his mistake

73
Q

What is the Local Group?

A

group of spiral galaxies (and some dwarf ellipticals) including the Milky Way, Andromeda, M-33, and others

74
Q

What is the approximate diameter of our Local Supercluster?

A

130 million light years

75
Q

What are the empty spaces between superclusters called?

A

voids

76
Q

Active Galaxies use up a lot of ___.

A

energy

77
Q

Where is the activity in an Active Galaxy usually located?

A

nucleus, Active Galactic Nuclei (AGN)

78
Q

Quasars are a type of ____ ____.

A

Active Galaxy

79
Q

Quasars emit huge amounts of ___.

A

radiowaves

80
Q

What was the first Quasar discovered named? Where was it discovered?

A

3C 273; Cambridge

81
Q

jet

A

material shot from the center of a galaxy

82
Q

3C 273 is very ____ when viewed via radio wavelengths and emits huge amounts of ____.

A

bright; radiowaves

83
Q

Ordinary stars are bright when viewed via ____ ___.

A

visible light

84
Q

What is ‘Quasar’ short for?

A

Quasi-Stellar Radio Source

85
Q

Most stars have ____ line spectrum, but 3C 273 has ___ line spectra.

A

absorption; emission

86
Q

Why didn’t the emission lines from 3C 273 match any known element?

A

It was H with the largest redshift ever observed.

87
Q

Why did H in 3C 273 have such a large redshift?

A

3C 273 is moving away very fast and is located very far away

88
Q

What are the 8 characteristics of Quasars?

A

1- emit large amounts of radiowaves
2- very bright when observed through radio wavelengths
3- emission line spectrum
4- emission lines for H with the largest redshift ever observed
5- farthest objects in the universe
6- moving away from us very fast
7- incredibly luminous and energetic
8- vary in brightness significantly on various timescales

89
Q

About how far away is a Quasar?

A

3 - 5 billion light years

90
Q

Quasars are the most ____ and ___ things in the universe.

A

luminous; energetic

91
Q

The energy output of a typical Quasar is comparable to ____ supernovas.

A

10,000

92
Q

3C 273 varies in brightness on a timescale of approximately a few ___.

A

months

93
Q

3C 273 is a ___(tame/wild)___ Quasar.

A

tame

94
Q

What is the max size of a Quasar like 3C 273?

A

about a light month

95
Q

Wilder Quasars will vary in brightness on timescales of about a ___. Their max size is about one light ___.

A

day; day

96
Q

Quasars have extremely bright ___.

A

nuclei

97
Q

What is the big mystery of Quasars and AGNs?

A

How do you get so much energy in such a small volume of space?

98
Q

What is the most reasonable theory for the Quasar/AGN mystery?

A

Rotating Supermassive Black Holes are at the center. Objects could pick up the black hole’s energy in the ergosphere. The objects are then shot out (like a slingshot), explaining jets.

99
Q

Galaxies near the Milky Way have settled down and may have ___ ___ ___ ___ in their centers. Why have they settled down?

A

rotating supermassive black holes; the black hole’s spinning has slowed down over time

100
Q

If both Quasars/AGNs and regular galaxies have rotating supermassive black holes, what does that mean for Quasars/AGNs?

A

They will eventually settle down to form regular galaxies as the rotating slows.

101
Q

What type of galaxy is M-87?

A

giant elliptical galaxy

102
Q

M-87 is not a Quasar, but it is very ___. It has a ___ on one side and a ___ on the other, suggesting that the galaxy is orbiting its ___.

A

M-87 is not a Quasar, but it is very active. It has a redshift on one side and a blueshift on the other, suggesting that the galaxy is orbiting its nucleus.

103
Q

Astronomers can use orbits like that of M-87 to determine ____.

A

distance (and other things)

104
Q

M-87 has helped astronomers assume that galaxies ___ ___ as they get older.

A

settle down

105
Q

What are the 2 major 20th century theories for the origin of the universe?

A

Big Bang Theory, Steady State Theory

106
Q

What are the two sub-theories under the Big Bang Theory?

A

Closed Big Bang and Open Big Bang

107
Q

What does the Big Bang Theory suggest?

A

there was a primeval fireball, the entire universe was compressed into a geometric point until it started expanding (raisin bread analogy)

108
Q

What does the Open Big Bang Theory suggest?

A

the universe will continue expanding

109
Q

What does the Closed Big Bang Theory suggest?

A

the fireball will expand to its max, then mass will cause it to collapse in on itself; this could end the universe

110
Q

What is the sub-theory under the Closed Big Bang Theory? What does it suggest?

A

Oscillating Big Bang; it’s a cycle, the universe will expand -> collapse -> expand

111
Q

What does the Steady State Theory suggest?

A

the universe (the average density or average distance between galaxies) does not change but the universe will continue expanding; H atoms will appear out of nothing every 500 million years, slowly forming new galaxies to keep the average distance between galaxies the same

112
Q

Newton’s Infinite Static Universe

A

in any direction, if you go far enough, you will find a star

113
Q

What is Olber’s Paradox?

A

If Newton’s Infinite Static Universe is true, how can the night sky be dark? It should be bright like the surface of a star.

114
Q

The rate at which the universe is expanding is ___. When was this discovered?

A

increasing; the 1990s

115
Q

Who discovered the Cosmic Background Spectrum? When?

A

Penzias and Wilson in the mid 1960s

116
Q

How did Penzias and Wilson discover the Cosmic Background Spectrum?

A

The designed an antenna meant to minimize background noise (static). There was one bit of noise they couldn’t locate or eliminate.

117
Q

What is the significance of the Cosmic Background Spectrum?

A

It is incredibly strong evidence confirming the Big Bang Theory, by confirming predictions made by the Theory. It also disproved the Steady State Theory.

118
Q

What is the Cosmic Background Spectrum?

A

microwaves; radiation left over from an early stage in the development of the universe; thermal radiation assumed to be left over from the “Big Bang” of cosmology

119
Q

What does the Cosmic Background Spectrum mimic?

A

black body 3º above absolute zero

120
Q

Why would the universe be emitting microwaves at 3º above absolute zero?

A

The Big Bang would have been hot at first, then cooled off to about 3º above absolute zero.

121
Q

The Big Bang stage of the history of the universe was the point of ___.

A

formation

122
Q

What are the 7 stages of the history of the universe?

A 
1- Big Bang
2- Inflationary
3- Hadron
4- Lepton
5- Radiation
6- Matter
7- Present
123
Q

What did the Inflationary stage in the history of the universe involve?

A

very rapid expansion in a very short amount of time

124
Q

During the Hadron stage in the history of the universe, ____ and similar particles came to be. There was ____ radiation and ___.

A

protons; electromagnetic; energy

125
Q

During the Lepton stage in the history of the universe, ____ and similar matter came to be. There was ____ radiation and ___.

A

electrons; electromagnetic; energy

126
Q

During the Radiation stage in the history of the universe, the temperature ___, forming ___ stars. __ is converted into He. The universe is __% He.

A

During the Radiation stage in the history of the universe, the temperature cools, forming cool stars. H is converted into He. The universe is 25% He.

127
Q

Matter stage of the history of the universe: Matter + Anti-Matter = ?

A

large release of energy equal to E=mc^2

128
Q

Why isn’t the Matter + Anti-Matter process a perfectly symmetrical process?

A

there is more matter than anti-matter

129
Q

What is converted to create Carbon?

A

He

130
Q

Why wasn’t Carbon formed prior to the present?

A

the universe was too cool to form C by the time He was formed

131
Q

What is Hubble’s Law (2 observations)?

A

the observation that:
1- objects observed in deep space have a Doppler shift (redshift/blueshift), meaning they are moving away from Earth at a relative velocity
2- this Doppler-shift-measured velocity is approximately proportional to the objects’ distance from the Earth

132
Q

What is the significance of Hubble’s Law?

A

It is a direct, physical observation of the expansion of the universe.

133
Q

___ ___ are the brightest stars.

A

Red Giants

Astronomy (5 decks)

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