Test 4 Flashcards
(134 cards)
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.
1
Q
The Milky Way is a collection of ___#___ stars in a _____ shape.
A
a few hundred billion stars; pancake
2
Q
What is the closest spiral galaxy to the Milky Way? How far away is it?
A
Andromeda; 2 million light years
3
Q
What is the diameter of a typical galaxy?
A
100,000 light years
4
Q
How many miles is a light year equal to?
A
6 trillion
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.
6
Q
How did Hershall attempt to measure the galaxy?
A
Star counts
7
Q
What was Hershall’s conclusion?
A
The Milky Way isn’t very big and we are in the center.
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.
9
Q
What did Harlow Shapley do?
A
He was an astronomer who counted globular clusters (rather than individual stars) to measure the galaxy.
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.
11
Q
Cepheid variable stars burn ____ in the core.
A
Helium
12
Q
Define period of a variable star.
A
Time it takes to go bright, faint, then bright again
13
Q
Luminosity allows us to find ____.
A
Distance
14
Q
What did Shapley mistakenly study?
A
RR Lyrae Stars
15
Q
What are the 5 parts of the Milky Way galaxy?
A
Nucleus, dust, gas lanes, disc, halo
16
Q
Our galaxy used to be ____, but ___ ___ ___ happened.
A
spherical; Pizza Dough Physics
17
Q
Where in the galaxy is the Sun located?
A
About 2/3 of the way between the center and the edge
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
19
Q
The galaxy is ____ massive than we thought.
A
more
20
Q
Recent evidence suggests the Milky Way is a ____ spiral galaxy.
A
barred
21
Q
How do we know the Milky Way has a spiral arm structure?
A
using H emitted radio waves, astronomers mapped it out
22
Q
Which goes through dust easier: optical light or radio waves?
A
Radio waves
23
Q
Spiral arms emit ____.
A
radio waves
24
Space between stars is filled with ___.
Hydrogen
25
What is the length of a radio wave emitted by H?
21 cm
26
H atoms in the ___ ___ of the galaxy emit ___ ___.
spiral arms; radio waves
27
Where does the Spiral Density Wave come from?
Center of Milky Way
28
What is the Spiral Density Wave's pattern?
Compressed, spread out, compressed, etc.
29
What is Sagittarius A?
First radio source discovered in Sagittarius constellation
30
Sagittarius A is very ____.
bright
31
What is Sagittarius B?
Second radio source discovered in Sagittarius constellation
32
What drives the Spiral Density Wave?
No one knows
33
Why do we get radio waves coming from the center of the galaxy?
Magnetic field; Synchrotron Radiation
34
The most energetic source in the core of the Milky Way is the size of a ____ ____.
solar system
35
What do we suspect is spinning at the Milky Way's core?
Super massive black hole
36
What makes a black hole super massive?
Small black holes merge
37
Who proved there were other galaxies?
Edwin Hubble
38
What is Extra-Galactic Astronomy?
Study of astronomy outside of the Milky Way
39
Edwin Hubble proved that the universe is ____.
expanding
40
Where did Edwin Hubble make his observations?
Telescope on Mt. Wilson
41
Who was Hubble's assistant?
Milton Humison
42
Who discovered the Andromeda Galaxy? How?
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.
43
How far away is Andromeda?
2 million light years
44
What is the Milky Way's approximate diameter?
100,000 light years
45
Hubble classified galaxies based on ____.
appearance
46
What are Hubble's 2 broad categories for galaxies?
Elliptical & Spiral
47
There are ____ and Giant Elliptical galaxies.
dwarf
48
How many types of Elliptical galaxies are there? How do they vary?
8 (E0-E7). E0 is spherical like a basketball. E7 is elongated like a football.
49
What are the 2 types if spiral galaxies?
Normal/Ordinary (S or SA) and Barred (SB)
50
What is an S0 galaxy?
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.
51
What are the 3 components of a spiral galaxy?
Nucleus, disc, halo
52
Describe an Sa galaxy.
Spirals compressed, tightly wound around nucleus
53
Describe an S0 galaxy.
Disc with no spirals
54
Describe an Sc galaxy.
Spirals spread out, loosely wound
55
An Sb galaxy is characteristically between ___ and ___.
Sa, Sc
56
Galactic Cannibalism
how galaxies accrete mass; merging with other galaxies
57
Hubble's Classes: Irregulars
galaxies that don't fit any of Hubble's classes; no shape
58
Hubble's Classes: pec
peculiar; a galaxy that doesn't perfectly fit a class
59
What are the 6 main properties of galaxies?
diameter, mass, luminosity, color, percentage of gas content, types of stars
60
How does a Giant Elliptical galaxy compare to the Milky Way?
bigger, brighter, more massive
61
How does a Dwarf Elliptical galaxy compare to the Milky Way?
smaller, less massive, fainter
63
What color is a sample of old stars?
Red
63
Describe the stars in an Irregular Galaxy.
young, blue, high percentage of gas
64
What color is a sample of young stars?
blue
65
What type of stars does an Elliptical Galaxy have?
old, red
66
What type of stars does a Spiral Galaxy, like the Milky Way, have?
mix of old and new, mix of red and blue
67
Elliptical Galaxies tend to be ___ with ___ gas content. They ___(are/ are not)___ forming new stars and appear ___ in color.
Elliptical Galaxies tend to be old with very little gas content. They are not forming new stars and appear red in color.
68
A cepheid variable star is a ___ indicator, sometimes called a ___.
distance; candle
69
The further away a galaxy is, the ___ it appears to be moving away from us.
faster
70
The Sun and similar stars can produce an HNK spectral line from ____.
Calcium
71
When did Hubble discover the universe was expanding?
1930s
72
What other scientist predicted the universe's expansion before Hubble? Why isn't he credited with the discovery?
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
What is the Local Group?
group of spiral galaxies (and some dwarf ellipticals) including the Milky Way, Andromeda, M-33, and others
74
What is the approximate diameter of our Local Supercluster?
130 million light years
75
What are the empty spaces between superclusters called?
voids
76
Active Galaxies use up a lot of ___.
energy
77
Where is the activity in an Active Galaxy usually located?
nucleus, Active Galactic Nuclei (AGN)
78
Quasars are a type of ____ ____.
Active Galaxy
79
Quasars emit huge amounts of ___.
radiowaves
80
What was the first Quasar discovered named? Where was it discovered?
3C 273; Cambridge
81
jet
material shot from the center of a galaxy
82
3C 273 is very ____ when viewed via radio wavelengths and emits huge amounts of ____.
bright; radiowaves
83
Ordinary stars are bright when viewed via ____ ___.
visible light
84
What is 'Quasar' short for?
Quasi-Stellar Radio Source
85
Most stars have ____ line spectrum, but 3C 273 has ___ line spectra.
absorption; emission
86
Why didn't the emission lines from 3C 273 match any known element?
It was H with the largest redshift ever observed.
87
Why did H in 3C 273 have such a large redshift?
3C 273 is moving away very fast and is located very far away
88
What are the 8 characteristics of Quasars?
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
About how far away is a Quasar?
3 - 5 billion light years
90
Quasars are the most ____ and ___ things in the universe.
luminous; energetic
91
The energy output of a typical Quasar is comparable to ____ supernovas.
10,000
92
3C 273 varies in brightness on a timescale of approximately a few ___.
months
93
3C 273 is a ___(tame/wild)___ Quasar.
tame
94
What is the max size of a Quasar like 3C 273?
about a light month
95
Wilder Quasars will vary in brightness on timescales of about a ___. Their max size is about one light ___.
day; day
96
Quasars have extremely bright ___.
nuclei
97
What is the big mystery of Quasars and AGNs?
How do you get so much energy in such a small volume of space?
98
What is the most reasonable theory for the Quasar/AGN mystery?
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
Galaxies near the Milky Way have settled down and may have ___ ___ ___ ___ in their centers. Why have they settled down?
rotating supermassive black holes; the black hole's spinning has slowed down over time
100
If both Quasars/AGNs and regular galaxies have rotating supermassive black holes, what does that mean for Quasars/AGNs?
They will eventually settle down to form regular galaxies as the rotating slows.
101
What type of galaxy is M-87?
giant elliptical galaxy
102
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 ___.
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
Astronomers can use orbits like that of M-87 to determine ____.
distance (and other things)
104
M-87 has helped astronomers assume that galaxies ___ ___ as they get older.
settle down
105
What are the 2 major 20th century theories for the origin of the universe?
Big Bang Theory, Steady State Theory
106
What are the two sub-theories under the Big Bang Theory?
Closed Big Bang and Open Big Bang
107
What does the Big Bang Theory suggest?
there was a primeval fireball, the entire universe was compressed into a geometric point until it started expanding (raisin bread analogy)
108
What does the Open Big Bang Theory suggest?
the universe will continue expanding
109
What does the Closed Big Bang Theory suggest?
the fireball will expand to its max, then mass will cause it to collapse in on itself; this could end the universe
110
What is the sub-theory under the Closed Big Bang Theory? What does it suggest?
Oscillating Big Bang; it's a cycle, the universe will expand -> collapse -> expand
111
What does the Steady State Theory suggest?
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
Newton's Infinite Static Universe
in any direction, if you go far enough, you will find a star
113
What is Olber's Paradox?
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
The rate at which the universe is expanding is ___. When was this discovered?
increasing; the 1990s
115
Who discovered the Cosmic Background Spectrum? When?
Penzias and Wilson in the mid 1960s
116
How did Penzias and Wilson discover the Cosmic Background Spectrum?
The designed an antenna meant to minimize background noise (static). There was one bit of noise they couldn't locate or eliminate.
117
What is the significance of the Cosmic Background Spectrum?
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
What is the Cosmic Background Spectrum?
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
What does the Cosmic Background Spectrum mimic?
black body 3º above absolute zero
120
Why would the universe be emitting microwaves at 3º above absolute zero?
The Big Bang would have been hot at first, then cooled off to about 3º above absolute zero.
121
The Big Bang stage of the history of the universe was the point of ___.
formation
122
What are the 7 stages of the history of the universe?
```
1- Big Bang
2- Inflationary
3- Hadron
4- Lepton
5- Radiation
6- Matter
7- Present
```
123
What did the Inflationary stage in the history of the universe involve?
very rapid expansion in a very short amount of time
124
During the Hadron stage in the history of the universe, ____ and similar particles came to be. There was ____ radiation and ___.
protons; electromagnetic; energy
125
During the Lepton stage in the history of the universe, ____ and similar matter came to be. There was ____ radiation and ___.
electrons; electromagnetic; energy
126
During the Radiation stage in the history of the universe, the temperature ___, forming ___ stars. __ is converted into He. The universe is __% He.
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
Matter stage of the history of the universe: Matter + Anti-Matter = ?
large release of energy equal to E=mc^2
128
Why isn't the Matter + Anti-Matter process a perfectly symmetrical process?
there is more matter than anti-matter
129
What is converted to create Carbon?
He
130
Why wasn't Carbon formed prior to the present?
the universe was too cool to form C by the time He was formed
131
What is Hubble's Law (2 observations)?
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
What is the significance of Hubble's Law?
It is a direct, physical observation of the expansion of the universe.
133
___ ___ are the brightest stars.
Red Giants
