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Astronomy
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1
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the study of galaxies
galactic astrophysics
2
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a collection of stars arranged into a more rounded shape near the center of a galaxy
galactic bulge
3
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stars around the galactic disk (above and below)
galactic halo
4
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the average duration of time it takes the Milky Way Galaxy to complete one rotation
galactic year
5
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how long is a galactic year?
between 200 and 250 million years
6
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streaming arcs of millions of stars swirling around the center of a spiral-disk galaxy
spiral arms
7
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are spiral arms permanent structures?
no
8
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the two major spiral arms of the Milky Way Galaxy
* Perseus Arm
* Scutum-Centaurus-Crux Arm
9
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minor spiral arms of the Milky Way Galaxy
\- Norma Arm \n - Carina-Sagittarius Arm \n - Orion Arm
10
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which spiral arm is our solar system located in?
the Orion Arm
11
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variations in stellar concentrations that propagate throughout all the stars in the Milky Way Galaxy
spiral density waves
12
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how far away is our solar system from the Milky Way Galaxy's galactic center?
roughly 25,000 light-years (8 kiloparsecs)
13
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how wide is the Milky Way Galaxy?
roughly 100,000 light years in diameter (30 kiloparsecs)
14
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how thick is the Milky Way Galaxy?
roughly 1,000 light years in thickness (300 parsecs)
15
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how many star systems make up the Milky Way Galaxy?
roughly 100 billion star systems
16
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the study of the shape and evolution of a galaxy
galactic dynamics
17
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a black hole that has spent billions of years gaining more and more mass
supermassive black hole
18
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what is the mass of a supermassive black hole?
millions of solar masses, sometimes billions
19
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what is at the center of every major galaxy?
a supermassive black hole
20
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a graph of the orbital speed of stars around the center of a galaxy as a function of their distance from the center of the galaxy
rotation curve
21
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what kind of rotation curve does every major spiral galaxy have?
a flat rotation curve
22
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dark matter distributed over an enormous sphere surrounding all the star systems of a galaxy
dark matter halo
23
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how much of the universe is made up of dark matter?
roughly 90%
24
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what does the theory of Massive Compact Halo Objects (MACHOs) say?
dark matter is an enormous number of brown dwarf stars in the galactic halo surrounding all the other stars of a galaxy
25
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what does the theory of Weakly Interacting Massive Particles (WIMPs) say?
dark matter is composed of exotic quantum-mechanical particles (Supersymmetric Relativistic Quantum Field Theory)
26
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very diffuse gas that fills the entire galactic disk
interstellar medium
27
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an area in interstellar medium that is more dense than average
diffuse nebula
28
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a diffuse nebula that absorbs light
absorption nebula
29
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what color do absorption nebulas appear as?
black
30
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a diffuse nebula that emits light
emission nebula
31
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what color do emission nebulas appear as?
red
32
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a diffuse nebula that reflects light
reflection nebula
33
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what color do reflection nebulas appear as?
blue
34
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the fraction of anything in the universe that is hydrogen
hydrogen fraction
35
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what is the hydrogen fraction for nearly everything in the entire universe?
roughly 75%
36
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the fraction of anything in the universe that is helium
helium fraction
37
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what is the helium fraction for nearly everything in the entire universe?
roughly 25%
38
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the fraction of anything in the universe that is not hydrogen or helium
metallicity
39
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stars inside the galactic disk with higher metallicity
Population I stars
40
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what is the metallicity of Population I stars?
1% or 2%
41
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stars outside of the galactic disk with some metallicity
Population II stars
42
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what is the metallicity of Population II stars?
roughly 0.1%
43
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the very first stars born in the entire universe made up of solely hydrogen and helium
Population III stars
44
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what is the metallicity of Population III stars?
0%
45
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the process that causes light that gets to us to be more red than the original light
reddening
46
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a star cluster inside the galactic disk
open star cluster
47
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what type of stars make up open star clusters?
mostly Population I stars
48
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a star cluster outside of the galactic disk
globular star cluster
49
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what type of stars make up globular star clusters?
mostly Population II stars
50
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what are properties of Population I stars?
hot, luminous, and blue
51
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what are properties of Population II stars?
cool, dim, and red
52
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what is the shape of open star clusters?
irregular
53
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what is the shape of globular star clusters?
spherical
54
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how many stars make up open star clusters?
several hundred
55
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how many stars make up globular star clusters?
hundreds of thousands
56
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where do you have to look in order to look towards the center of our Milky Way Galaxy?
in the direction of the constellation Sagittarius
57
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young open star clusters embedded within the diffuse nebula from which they formed
embedded star clusters
58
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star clusters with a significant number of O-type and B-type stars
OB associations
59
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a cavity hundreds of light years across that surrounds OB associations
superbubble
60
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the area in the sky that is in the direction of the "milky way" in the sky, opposite of the constellation Sagittarius
galactic anticenter
61
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where is the galactic anticenter located?
near the intersection of the constellations Auriga, Gemini, and Taurus
62
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a galaxy that orbits another galaxy
satellite galaxy
63
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where did SN1987A occur?
in the Large Magellanic Cloud
64
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what are the main satellite galaxies of the Milky Way Galaxy?
* Canis Major Dwarf Galaxy
* Sagittarius Dwarf Galaxy
* Small Magellanic Cloud
65
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how far away is the Canis Major Dwarf Galaxy?
roughly 25,000 light-years (8 kiloparsecs)
66
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how far away is the Sagittarius Dwarf Galaxy?
roughly 75,000 light-years (25 kiloparsecs)
67
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how far away is the Large Magellanic Cloud?
roughly 150,000 light-years (50 kiloparsecs)
68
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how far away is the Small Magellanic Cloud?
roughly 200,000 light-years (60 kiloparsecs)
69
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a list of one hundred and ten faint objects in the sky
Messier deep sky catalog
70
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M1 on the Messier catalog
the Crab nebula
71
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what type of nebula is the Crab nebula?
a supernova remnant
72
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M13 on the Messier catalog
the Hercules cluster
73
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what type of star cluster is the Hercules cluster?
a globular star cluster
74
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M31 on the Messier catalog
Andromeda Galaxy
75
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the closest major galaxy to the Milky Way Galaxy
Andromeda Galaxy
76
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how far away is the Andromeda Galaxy?
roughly 2.5 million light-years (800 kiloparsecs)
77
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what type of galaxy is the Andromeda Galaxy?
a spiral-disk galaxy
78
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how large is the Andromeda Galaxy?
roughly the same size as the Milky Way Galaxy
79
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M33 on the Messier catalog
Triangulum Galaxy
80
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how far away is the Triangulum Galaxy?
roughly 3 million light-years (over 800 kiloparsecs)
81
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what type of galaxy is the Triangulum Galaxy?
a spiral-disk galaxy
82
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how large is the Triangulum Galaxy?
roughly 1/10th the size of the Milky Way Galaxy
83
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M42 on the Messier catalog
the Orion nebula
84
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what type of nebula is the Orion nebula?
a diffuse nebula
85
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M45 on the Messier catalog
the Pleiades cluster
86
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what type of star cluster is the Pleiades cluster?
an open star cluster
87
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M57 on the Messier catalog
the Ring nebula
88
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what type of nebula is the Ring nebula?
a planetary nebula
89
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variable stars in a star cluster that are protostars
Tauri variable stars
90
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variable stars in a star cluster that are asymptotic-giant-branch stars
Cepheid variable stars
91
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variable stars in a star cluster that are horizontal-branch stars
Lyrae variable stars
92
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an equation relating the average luminosity of Cepheid variable stars with their pulsation period
Leavitt period-luminosity relation
93
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the 3 major galaxies in the Local Galactic Group
* Milky Way Galaxy
* Andromeda Galaxy
* Triangulum Galaxy
94
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how many galaxies are in a typical galactic group?
several dozen
95
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how many major galaxies are in a typical galactic group?
less than 10
96
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how many major galaxies are in a typical galactic cluster?
several hundred
97
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how many galaxies are in the Local Galactic Group?
several dozen
98
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how many major galaxies are in the Local Galactic Group?
3
99
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an enormous region between galactic superclusters that is nearly completely empty of galaxies
cosmic void
100
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what do multiple galaxies clumped together form?
a galactic group or galactic cluster
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