ast 109 > prelim 3 > Flashcards

prelim 3 Flashcards

(102 cards)

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1
Q

what is a spectrum?

A

light broken into wavelengths that tell us temperature, motion, and chemical makeup

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2
Q

what tool separates light into a spectrum?

A

a spectrograph

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3
Q

what information can a spectrum tell us?

A
  • elements present
  • stars temperature
  • motion (Dopplers shift)
  • density
  • mass and age (with models)
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4
Q

what determines an atoms element?

A

number of protons

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5
Q

what are the 3 main particles of atoms?

A
  • protons (+)
  • neutrons (0)
  • electrons (-)
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6
Q

what makes an atom neutral?

A

equal protons and electrons

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7
Q

what is absorption?

A

electron absorbs a photon - jumps to a higher energy level

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8
Q

what is emission?

A

electron drops - releases a photon

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9
Q

what determines photon energy?

A

the difference between energy levels

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10
Q

what is an isotope?

A

same element, different number of neutrons

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11
Q

what is a molecule?

A

atoms bonded by sharing electrons

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12
Q

what produces a continuum spectrum?

A

hot, dense objects (star surface)

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13
Q

what produces an absorption spectrum?

A

cool gas in front of a hot surface

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14
Q

what produces an emission spectrum?

A

hot, thin gas glowing on its own

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15
Q

what causes the dark lines in a stars spectrum?

A

elements absorbing certain wavelengths

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16
Q

what is an ion?

A

a charged atom with more/less electrons than protons

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17
Q

where are ions commonly seen?

A

in comet tails

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18
Q

what is the big lie about electron orbits?

A

we draw electrons in neat circles, but they actually exist in fuzzy clouds

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19
Q

what did Bohr get right?

A

electrons have only certain allowed energies

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20
Q

what is the formula for photon energy?

A

E = hc/λ

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21
Q

what happens to energy if wavelength gets longer?

A

energy decreases

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22
Q

which is higher energy: Lyman or Balmer?

A

Lyman (UV, shorter wavelengths, more energy)

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23
Q

what is a continuum spectrum?

A

smooth rainbow of color - from a hot, dense object

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24
Q

what causes an absorption spectrum?

A

cool gas in front of a hot source - dark lines appear

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25
what causes an emission spectrum?
hot thin gas glowing by itself - bright color lines
26
what does Wien's Law say?
hotter objects peak at shorter wavelengths (bluer)
27
what color are hotter stars?
blue
28
what color are cooler stars?
red
29
what does star color show?
temperature- blue = hotter, red = cooler
30
why do stars have absorption lines?
cool outer layers absorb certain wavelengths
31
why do absorption lines differ by temperature?
different temperatures excite/ionize atoms differently
32
what is the order of spectral types?
O B A F G K M (hot to cool)
33
what do numbers 0-9 mean?
0 = hottest, 9 = coolest
34
what class is the sun?
G2
35
what does the stars absorption lines depend on?
temperature- because electrons occupy different energy states
36
what is the mnemonic for the stellar temperature sequence?
Oh Be A Fine Girl Kiss Me
37
O stars
- blue/white - 30,000-50,000 K - weak hydrogen lines (ionized) - strong helium lines
38
B stars
-blue/white - 11,000-30,000 K - stronger hydrogen lines
39
A stars
- white - strongest hydrogen (Balmer) lines
40
F stars
- yellow/white - strong calcium lines
41
G stars
- yellow - sun-like - weak hydrogen lines
42
K stars
- orange - more metal lines
43
M stars
- red - the coldest - no hydrogen (Balmer) lines - many molecule lines
44
why are Balmer lines strongest in A stars?
hydrogen electrons are mostly in the n = 2 state
45
why are Balmer lines weak in very hot stars?
hydrogen is ionized
46
why are Balmer lines weak in cool stars?
electrons rarely reach n = 2
47
what is the suns classification?
G2V
48
what is the sun made of?
94% hydrogen atoms, 6% helium atoms
49
what is the suns surface temperature?
5800 K
50
what is the suns core temperature?
15 million K
51
how long if the sunspot cycle?
11 years
52
how often does the magnetic field flip?
every 22 years
53
why do sunspots form?
twisted magnetic fields block convection - cooler spots
54
photosphere
- visible surface - 5,800 K - granules from convection
55
chromosphere
- red - spicules and supergranules - 4,000-10,000 K
56
corona
- very hot (1-2 million K) - thin - visible in eclipse only
57
solar wind
flow of charged particles from corona - causes auroras
58
suns radiative zone
light moves slowly outward
59
what is a flare?
magnetic explosion that increases solar wind - can disrupt satellites
60
what are prominences/filaments?
loops of cool gas above the sun - bright when seen against space (prominence) - dark when seen against sun (filament)
60
what are sunspots?
cool, dark, magnetically active regions
61
what is plage
bright magnetic patches above sunspots
62
what powers the sun?
nuclear fusion (hydrogen to helium)
63
what are the suns interior layers?
1. core 2. radiative zone 3. convective zone
64
suns temperature
core: 15 million K surface: 5,800 K
65
what is the sunspot cycle?
- 11 year cycle of number of spots - 22 year magnetic polarity flip
66
why does the magnetic field twist?
sun rotates faster at equator than poles
67
suns convection zone
hot gas rising/falling moves energy quickly
68
what is parallax?
apparent shift of a star as Earth orbits
69
larger parallax = ?
closer star
70
what do lower magnitudes mean?
brighter stars
70
what is apparent magnitude?
how bright a star looks from Earth
71
what is absolute magnitude?
brightness at 10 parsecs- removes distance effects
72
what does the H-R diagram compare?
temperature (left/right) vs luminosity (up/down)
73
what does the H-R diagram show?
star size, age, and type
74
how do we measure star masses?
from the orbital motion of binary stars
75
what is a parsec?
distance where parallax = 1 arcsecond
76
does lower magnitude mean brighter?
yes - more negative = brighter
77
main sequence
hydrogen to helium fusion
78
red giants
big, cool, and bright
79
white dwarfs
small, hot, and dim
80
what is a spectroscopic binary?
lines shift back and forth due to Doppler effect
81
what is an eclipsing binary?
one star passes in front of another, causing dips in brightness
82
what are Bok globules?
dark clouds where stars form
83
what triggers collapse?
jeans instability (gravity > pressure)
84
mass range 1
<0.08M - brown dwarfs (never reach fusion)
85
mass range 2
0.08-0.4 M - red dwarfs - live up to a trillion years - eventually become helium white dwarfs
86
mass range 3
0.4-8 M - sun-like stars
87
mass range 4
8-25 M - massive stars
88
mass range 5
>25 M - very massive stars
89
what is jeans instability?
gravity beats pressure (cloud collapses)
90
what is a protostar?
a collapsing cloud hot enough to emit infrared
91
what is the birthline of a protostar?
when the new star becomes visible and blows away its remaining cloud
92
what fuels main sequence stars?
core hydrogen fusion
93
how does mass affect lifetime?
more mass = shorter lifetime
94
what makes a star expand into a red giant?
hydrogen burning in the shell dumps energy into the outer layers
95
what is a helium flash?
sudden start of helium at 100 million K
96
what is planetary nebula?
a dying stars outer layers pushed into space
97
what supports a white dwarf?
electron degeneracy pressure
98
what is a nova?
a white dwarf ignites newly accreted hydrogen in a surface explosion
99
what do main sequence stars do?
fuse hydrogen into helium in the core
100
what is left behind from a planetary nebula?
a white dwarf supported by electron degeneracy pressure
ast 109
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