Exam 2 Flashcards
(247 cards)
1
Q
Flux
A
Amount of power emitted per unit area. Watts/m^2
2
Q
Luminosity
A
Total power coming from object. L = Flux x Surface Area. Units = Watts
3
Q
Brightness
A
Flux. Power passing through a unit area. Watts/m^2 = Luminosity / 4 pi distance^2
4
Q
Stephan Boltzman Law
A
Flux = σ × T^4
5
Q
Emission rules
A
Hotter objects emit more light at all frequencies per unit area. Hotter objects emit photons with a higher average energy. (bluer photons)
6
Q
Wien’s Law
A
max wavelength in nm = 2.9 x 10^6 / T(K)
7
Q
Blueshift
A
Light emitted from object moving towards you has its wavelength shortened
8
Q
Redshift
A
Light emitted from object moving away from you will have wavelength lengthened
9
Q
Greater shift means
A
Greater speed in that direction
10
Q
Types of telescopes
A
Refracting and reflecting
11
Q
Refracting
A
2 lenses. The objective is large to collect as much light as possible and the eyepiece taes the focused light from the first and produces and image.
12
Q
Magnification
A
F(o)/F(e)
13
Q
Light gathering power proportional to
A
D^2
14
Q
Yerkes Observatory
A
Very huge
15
Q
Pros of refracting telescopes
A
Clear
16
Q
Cons of refracting telescopes
A
Long telescope tubes sag under gravity. Long telescope tubes mean BIG doms. Large objective means big piece of glass, which is heavy and make the tube sag, hard to make without impurities that scatter light, and light absorption through the lens. There is chromatic aberration.
17
Q
Chromatic aberration
A
Focal point for blue light is before focal point for red light; fringes of color on edges
18
Q
Reflecting telescopes
A
More common now. Made with curved mirrors to collect light. Parabolic cross section brings all parallel light rays to focus at same point.
19
Q
Why bigger size for reflecting?
A
Keck is 10 meters in diameter. 1) Larger light collecting area 2) Better angular resolution
20
Q
Angular resolution
A
Minimum angular separation that the telescope can distinguish. Smaller is better
21
Q
Resolving power
A
Diffraction limit: α(in arcsec) = 2.5 ×10^5 λ/D
22
Q
Radio telescopes
A
Huge wavelengths overpowers huge diameter. Angular resolution from single radio telescopes is only 1 arc minute or worse. Tens to hundreds of times worse than optical telescopes.
23
Q
Interferometry
A
Radio telescopes combine the light they see to synthesize the image that would be taken by a telescope with a diameter equal to the greatest separation between individual dishes. Gives very sharp images.
24
Q
Seeing
A
Light from stars is blurred by passing through atmosphere. This is why they twinkle.
25
Adaptive optics/ CCDs
Rapid changes in mirror shape to compensate for atmospheric turbulence. The more air the starlight passes through, the blurrier it gets. So putting telescopes on mountain tops or in space helps.
26
Observing problems due to Earth's atmosphere
1) light pollution 2) turbulence causes twinkling/blurry, so put it in space 3) atmosphere absorbs most of EM spectrum, including all UV and X ray, most infrared
27
How do telescopes help us learn more about universe?
1) collect more light than our eyes (due to area) 2) can see more details than our eyes (angular resolution) 3) can detect light that is invisible to our eyes like infrared, UV,
28
Two most important aspects of telescope
Light collecting area and angular resolution
29
Pros of reflecting telescopes
Light pases through the lens of refracting telescopes, so they have to be made of high quality glass precisely shaped on both sides. But reflecting surface of mirror must be shaped well only, not the other side. Quality of glass doesn't matter. Primary weight of glass is mounted at bottom of telescope, lot smaller issue.
30
Composition of Solar System
Sun, Jupiter, 7 other planets, 100+ moons, millions of smaller bodies
31
Details of Solar System (5)
1- One medium size star 2- Four small, rocky worlds, the terrestrial planets and four large, gaseous and liquid worlds, (the jovian planets) 3- 100 moons made of ice/rock 4- several 10^5 rocks less than 1000 km in size which are asteroids and 5- up to 10^12 objects made of ice/rock mixtures
32
Wavelengths of light smallest to largest
Gamma, X ray, UV, infrared, radio
33
Power proportional to (for telescopes)
size of lens area
34
Four major features of our solar system
1) orderly motions 2) two types of planets 3) comets and asteroids 4) exceptions to rules
35
Orderly motions of large bodies in solar system
planets orbit cc in same plane. orbits are nearly circular. sun and most planets rotate cc. most moons orbit cc.
36
density
= mass/volume. unitis are g /cm^3
37
Two types of planets (which are which)
mercury, venus, earth, mars are terrestrial. they are small, rocky, and close to the sun. the others are jovian, are large, gaseous, and far from the sun.
38
Comets and asteroids
Rocky asteroids between mars and jupiter. Icy comets around Neptune and beyond.
39
Exceptions
Uranus and pluto are tilted on their sides. Venus rotates clockwise. Earth is the only terrestrial planet with a relatively large moon. the orbit of pluto is more than 7 degrees different from the rest
40
Nebular Theory
Our solar system formed from a giant swirling cloud of gas and dust. The solar nebula (cloud) collapsed under its own gravity.
41
What does Nebular Theory depend on
Physics: Law of Gravity, Conservation of Energy, Conservation of angular momentum. Chemistry.
42
Observational evidence
Stars in the process of forming today are always found within interstellar clouds of gas. disks around other stars could be new planetary systems in formation
43
Cycle of gas
Stars are born in clouds of gas and dust. Stars produce heavier elements from lighter ones. Stars return material to space when they die. This gas gave birth to our solar system. Our gas cloud 98% hydrogen and helium and 2% everything else
44
Gravitational Collapse of Solar Nebula
Solar nebula initially somewhat spherical and a few light years in diameter. very cold and rotating slightly. it was given a push by some event, maybe a shock wave from a nearby supernova. as the nebula shrank, gravity increased, causing collapse. as the nebula falls inward, gravitational potential energy is converted to heat. as its radius decreases, it rotates faster
45
Nebula Theory and Orderly Motion
Nebula collapses and clumps of gas collide and merge. Random velocities average out into the nebula's direction of rotation. The spinning nebula assumes the shape of a disk. Collisions flatten out the cloud into a disk. collisions reduce the randomness of motion and reduce up and down motion. The sun formed in the center because temperature and density were high enough to for nuclear fusion. Planets formed in the rest. explains the fact that all planets lie along one plane, orbit in one direction, so does sun, planets tend to rotate in same direction, most moons orbit in this direction, most planetary orbits are near circular
46
Terrestrial planets
smaller size and mass, higher density of rocks and metals, solid surface, closer to sun and closer together, warmer, fewer moons and no rings
47
Jovian planets
larger size and mass, lower density with light gases and hydrogen compounds, no solid surface, farther from sun and further apart, cooler, rings and many moons
48
Nebula Theory and 2 types of planets
Gravity causes cloud to contract and heat. Inner parts and hotter than outer parts. Rock can be solid at much higher temperature than ice. only rocks and metals condensed within the frost line. Hydrogen compounds/ices condensed beyond the frost line. condensation - elements and compounds began to condense and solidify out of the nebula depending on the temp. accretion - stick to one another via electromagnetic force until they form planetesimals to combine near sun to form rocky planets or beyond frost line to form icy planetesimals which can capture H/He far from Sun to form gas planets. from gravity. each gas planet formed its own mini solar nebula, and moons formed out of that disk.
49
Frost Line
3.5 AU
50
Why are there two types of planets?
1) outer planets get bigger because abundant hydrogen condense to form ice. 2) Outer planets accrete and keep H and He gas because they're bigger. They can have a large number of moons.
51
Comets and Asteroids and Nebular theory
outflowing matter from sun, the solar wind, blew away leftover gases but not leftover planetesimals. these that did not accrete onto planets are the present day asteroids. The leftover icy ones are comets.
52
Asteroid Belt
Between Mars and Jupiter. Jupiter's gravity prevented a planet from forming there.
53
Kuiper Belt
Nebular theory predicted it 40 years before it existed. comets beyond neptune's orbit remained in the ecliptic plane called the Kuiper belt
54
Oort Cloud
comets which were located between the jovian planets, if not captured, were flung in all directions into the Oort cloud
55
Asteroids are rocky and comets are icy
because asteroids formed inside the frost line and comets formed outside
56
Exceptions and nebular theory
impacts - heavy bombardment period, first 10^8 years of the SS, they collided with the new planets and moons, which is why some moons orbit opposite, why some planets are tilted, why some rotate more quickly, why earth is the only terrestrial planet with a large moon.
57
Giant Impact Theory
formation of the moon. earth was struck by mars size planetesimal and part of earth's mantle was ejected, which coalesced into the moon. moon orbits in the same direction, with lower density. earth was spun up
58
Radiometric Dating
isotopes that are unstable are radioactive and decay. the time it takes for half to decay into other isotopes is half life.
59
Age of solar system
4.6 billion years from meteorites. radioactive isotopes formed in stars and supernova, so ss formation triggereed by supernova. nearby, since short half lives. we have to find rocks that have not melted or vaporized since they condensed from the solar nebula. geologic processes on Earth cause rock to melt and resolidify. earth rocks cant be used to measure the solar system's age. (radiometric dating measures the age of a rock since it solidified)
60
Mercury
lots of craters, smooth plains, cliffs
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Moon
lots of craters, smooth plains
62
Venus
volcanoes and few craters.
63
Mars
some craters, volcanoes, and maybe riverbeds. canyons.
64
Earth
volcanoes, craters, mountains, riverbeds
65
Three layers of planets
Core made of metals. Mantle made of dense rock. Crust made of less dense rock.
66
Lithosphere
Lithosphere is rigid outer layer of crust and part of mantle which doesn't deform easily, floats on the lower layers, thickness controls geological processes
67
Active geology on
Earth and venus
68
Inactive geology on
mars, mercury, moon
69
Sources of internal heat
gravitational potential energy of accretion, differentiation, radioactivity
70
Differentiation
layers ordered by density, highest density on bottom, gravity sorts materials by density. differentiation converts gpe to heat.
71
Radioactivity
is what supplies heat throughout the planets life. accretion and differentiation supply at the beginning
72
Which cools off faster, a big terrestrial or tiny one
conduction - heat flowing on micro level, convection, on macro level (hot rock rises). eruptions of lava. radiation of energy into space. A large planet is: still warm inside, has a convecting mantle, thinner, weaker lithosphere, molten rock near surface, making it more geologically active.
73
Planetary magnetic fields
moving charged particles created magnetic fields. so can a planet's interior, if the core is electrically conducting, convecting, and rotating.
74
Earth's magnetosphere
protects us from charged particles from Sun which can create aurora. switched direction many many times in earth's history. generated by motion of liquid outer core and to a lesser extent, rotation of the solid inner core
75
If a planet core is cold, does it have magnetic fields?
No, magnetic fields are generated by moving charges around. Core is cold, nothing is moving
76
How do we know what is inside Earth
Seismic waves generated by earthquakes probe Earth's interior
77
Major geological processes that shape planetary surfaces
Impact cratering, volcanism, tectonics, erosion
78
Impact cratering not visible on Earth because
erased by volcanic activity and the erosion
79
The more crater, the _____ the surface
Older
80
Importance of volcanism
Erases other geological features, provided gas for our atmosphere, provided water for our oceans
81
Why doesn't Mars have as much volcanic activity as Earth?
It's smaller so it cooled off faster
82
Tectonics. ____ is required
Surface reshaping from forces on the lithosphere. Internal heat required
83
Plate tectonics. Only ___ has it.
pieces of lithosphere moving around. only earth has it. warmer material rises to surface and motel rock oozes out between crustal plates, pushing them apart. volcanoes and earthquakes are caused by this.
84
Erosion can be caused by 3 things
wind, water, ice,
85
How does Earth's atmosphere affect Earth? 4
Erosion, protection from radiation, changes the surface temperature with greenhouse effect, and makes the sky blue
86
Radiation protection
X rays are absorbed very high in atmosphere, and UV absorbed by ozone
87
Greenhouse Effect
Visible light pases through the atmosphere. Surface absorbs it and emits thermal radiation as infrared. Greenhouses gases (H20, C02, CH4) absorb and re-emit infrared radiation, thereby heating the lower atmosphere.
88
Greenhouse gas
molecules with two different types of elements
89
What features of Earth are important for life? 4
1) surface liquid water 2) atmospheric oxygen 3) plate tectonics 4) climate stability
90
Why is the sky blue
the atmosphere scatters blue light much more than red light so that blue light reaches you from all directions in the sky. at sunset or sunrise, the light must pass through more atmosphere, so most blue light is scattered away, leaving red light.
91
What makes water possible
earth's distance from sun. moderate greenhouse effect.
92
Why is there water on Earth
water and other ices brought by planetesimals from more distant areas. water and gases trapped beneath surface. volcaic eruptions released them into atmosphere and the water rained down to form oceans
93
Atmospheric Oxygen made up of
Nitrogen and oxygen. photosynthesis produces is.
94
Plate tectonics are important because
carbon dioxide cycle - volcanoes outgas CO 2
95
How does CO2 cycle act like thermostat for Earth
Extended cold spell causes oceans to freeze. Ice forms, volcanoes release CO2 in atmosphere. Lowered reflectivity causes further cooling. Frozen oceans stop CO2 cycle so CO2 outgassed by volcanism builds up in atmosphere. Strong greenhouse effect melts the ice, and Earth becomes hot. CO2 cycle restarts, pulling CO2 into oceans, reducing greenhouses effect to normal.
96
connections between these unique features
plate tectonics creates climate stability. which allows for liquid water. which is necessary for life. which is necessary for atmospheric oxygen.
97
Mercury and the Moon are ___
geologically dead
98
Why is Venus so hot
greenhouse effect. thick CO2 atmosphere of venus locks heat in
99
Earth's CO2 is where?
in rocks. venus lacks oceans to dissolve CO2 and lock it away in rock on seafloor. that is because it is closer to sun and would be hotter by 30 C, runaway greenhouse effect.
100
Mars vs. Earth
Mars is smaller.
101
Once water on Mars?
Riverbeds, eroded craters. Water froze under surface. Velocity of gas depends on temp. Light, warm gas might have escaped the gravity of planet over time. When Mars was warmer, atmosphere leaked away into space. The water/ CO2 that was left froze into the ground and polar caps, further thinning the atmosphere.
102
Mars doesnt have ___ ___, so no way to recycle the carbon absorbed by sediments beneath the water
plate tectonics
103
Why doesnt mars have water
Mars’ interior solidified; the volcanoes went quiet. Mars’ lower gravity
allowed the atmosphere to begin to seep into space, reducing the
greenhouse effect and cooling the surface. Water and later CO2
froze into
ice, leaving only a thin remnant atmosphere. Some of the ice is at the
poles, but more might lie buried just below the dusty surface.
104
What makes a planet habitable
Located at optimal distance from sun for liquid water. Large enough for geological activity to release and retain water and atmosphere
105
Jupiter and Saturn VS Uranus and Neptune
Uranus and Neptune have less than 50% H and He, rest are hydrogen compounds and some more dense metal and rock. Jupiter and Saturn almost all gas and less dense.
106
Why Jovian planets different
Beyond frost line, ICE. So hydrogen compounds are more abundant than rock or metal and they got bigger and acquired H/He atmosphere
107
Amount of H/He gases accumulated are different in Jovian planets because
Timing - earliest formation gets most gas, as leftover blown away by solar wind. Location - the denser areas form their cores first.
108
How does Venus differ from Earth
Runaway greenhouse effect (close to Sun so high evaporation --> higher greenhouse --> higher evaporation), 90 atm pressure, 740 K
Rotates Clockwise
Not much erosion
No wind since rotation rate is so low
109
How does Mars differ from Earth
Runaway greenhouse effect (close to Sun so high evaporation --> higher greenhouse --> higher evaporation), 90 atm pressure, 740 K
Rotates Clockwise
Not much erosion
No wind since rotation rate is so low
110
Differences in terrestrial planets are explained by 3
Planetary size (internal heat/geology), distance to sun (too far, too cold for water, limiting erosion), Rotation
111
Extrasolar planets
we measure their wobble/ doppler shift in absorption line of spectrum since we cant see them
112
intensity of star changes
over life?
113
What is sun made of
solar wind, corona, chromosphere, photosphere, convection zone, radiation zone, core. hydrogen 70%, helium 28%, and carbon, nitrogen, oxygen, small elements
114
How does sun shine
Gravitational contraction provided energy that heated core as the Sun was forming. which stopped when fusion began. Gravitational equilibrium: energy provided by fusion maintains the pressure (keeps core hot and dense) The balance between inward pull of gravity and outward pressure of energy release. Sun radiates from surface exactly how much it produces in its core.
115
sunspot
are cooler than other parts of the Sun's surface (4000 K). regions with strong magnetic fields. with umbra and penumbra. cooler than photosphere because high magnetic field redirects the convection from the lower layers. the magnetic field at the sunspot is 1000 times greater than the rest of the Sun.
116
Sunspot Cycle
the number of sunspots rises and falls with and 11 year period. the sun switches the polarity of its magnetic field every two cycles or 22 years. it has something to do with the twisting of sun's magnetic field
117
Solar Flare
caused by magnetic activity. sends bursts of x rays and charged particles into space.
118
Corona
outermost layer of solar atmosphere, 1 million K. appears brighter in x ray photos in places where magnetic fields trap hot gas
119
Chromosphere
below corona, the density increases dramatically into the reddish chromosphere, but the temp drops from 1 million to 10,000 K. the chromosphere is the middle layer of the solar atmosphere
120
Photosphere
visible surface of the sun, 5800 K. sometimes spots are visible. granulation is seen, which are roughly the size of continents on earth. they ar rising bubbles of gas on the Sun.
121
Core
Radiation zone: energy transported upwards by photons. Core: energy generated by nuclear fusion at 15 million K
122
Differential Rotation
Convection combined with the rotation pattern of the Sun, faster at the equator than at the poles, causes solar activity because these gas motions stretch and twist Earth's magnetic field.
123
Helioseismology
Patterns of vibration on surface can tell us about what sun is like inside. results agree well with mathematical models.
124
Solar Neutrinos
Neutrinos created during fusion fly directly through the sun. observations of these solar neutrinos can tell us what's happening in the core. The first observations of neutrinos from the Sun conclusively proved that fusion powered the Sun. However, it was discovered that we saw only a third of the expected number of neutrinos. 3 types: electron, muon, tau. now we find the right number, but some have changed form.
125
Conduction
heating
126
Convection
Rising hot gas takes energy to surface after energy gradually leaks out of radiation zone in form of randomly bouncing photons.
127
Thermonuclear Fusion
Fusion process in Sun
128
Binary Star types.
orbit of a binary star system depends on strength of gravity. visual binary. eclipsing binary. spectroscopic binary. half of stars are binary.
129
Inverse Square Law
intensity is proportional to 1/distance^2, like newtons universal law of gravity
130
HR diagram
plot the temperature or spectral type vs luminosity
131
___ % of all stars lie on the Main sequence
90% of all stars lie on the main sequence
132
spectral types
lines in a star's spectrum correspond to a spectral type that reveals its temp hottest O B A F G K M L (oh be a fine guy, kiss me) 50,000 K to 3,000 K. they are defined by the existence of absorption lines belonging to various elements, ions, and molecules in the star's spectrum and the relative strength of these lines. but they are not determined y a star's composition. spectral types determined by a star's surface temperature!!!!
133
Parallax
the apparent shift in position of a nearby object against the background of a more distant object. apparent wobble of a star due to Earth's orbiting of the Sun. apparent positions of nearby stars shift by 1 arcsecond as earth orbits Sun. Parallax angle depends on distance. d = 1 AU/ p or d = 206,265 AU/ p for p in parsecs
134
Parsec
1 parsec ≡ 206,265 A.U. = 3.26 light years = 3.09 x 10^16 m
135
Variable Stars
Vertical region on HR diagram where all stars within it except those on MS are variable. This is instability strip. Because of lack of fuel in the core of the star, it does not remain in equilibrium!
136
Cepheid Variables
F-G bright giants whose pulsation periods get longer with brightness (luminosity). distance indicator
137
Globular Clusters
10^5 stars, 8 to 13 billion years old, spherical, no gas or nebulosity
138
Where do stars form
Nebula. molecular clouds consisting of hydrogen molecules. Stars are born from condensations in clouds of gas and dust. when they turn on, they cause the nebula to glow.
139
Why do stars form
Gravity can overcome thermal pressure in a cloud. Cloud heats up because gravity causes it to contract. conservation of energy says it continues if thermal energy is radiated away. it spins faster and faster as it becomes smaller. (conservation of angular momentum)
140
life of low mass star
main sequence, red giant branch, horizontal branch, .... core burning, shell burning, .... p-p chain ... H, He, C .... planetary nebula ...
white dwarf
141
life of a high mass star
main sequence, red giant branch, horizontal branch, ....
core burning, multiple shells burning, .... CNO cycle, He capture reaction, heavier nuclear reactions .... H, He, C, Mg – Fe .... supernova
142
Red Giant
• Red giants are giants stars that appear red because their tempartures are less than 4000 K (upper right). H fuses to He in shell around inert He core
143
white dwarf
White dwarfs are on the lower left. they are whats left behind after the planetary nebula blown away. burned out, carbon.oxygen core of a dead low mass star. very dense
144
planetary nebula
when low mass stars eject their outer layers, they form a planetary nebula. low mass stars dont have enough gravity to cause carbon fusion after He runs out. the C core collapses. the He and H burning shells overcome gravity and are blown away into nebula
145
supernova
for large stars, as iron core collapses, temp goes so high that the thermal gamma ray photons disintegrate the iron. the core is so dense that electrons are absorbed by protons in the atomic nuclei, forming neutros and releasing energetic neutrinos. the core pressure is robbed and the collapse accelerates until nuclear forces become repulsive. blasts out into supernova
146
supernova remnant
the expanding gas clouds left over from supernova explosions are mix of H/He left near surface of the star and the layers of new elements. the clouds expand and cool, joining with other gas clouds and forming new stars
147
neutron star
remains of core after supernova when neutrons collapse to center
148
black hole
a
149
small angle formula
α(in degrees) = (360/(2×π)) * R/d
| α(in arcsec) = 206,265R/d
150
Fusion
Only where it's15 million K. since protons repel one another. Fuses four hydrogen nuclei into one helium nucleus, producing energy and 2 neutrinos, 2 gamma rays, 2 positrons. 0.007 mass used. Sun will burn for 10 billion years
151
Solar Thermostat
Temp decreases, fusion decreases, core compresses, temp restored.
152
Solar Prominences
The magnetic field loops that create sunspots can funnel gas through space to create arch-shaped prominences. these bubbles of gas can last from hours to days. quiescent prominences last for days. active prominences last for short periods.
153
solar activity and humans
solar flares can cause coronal mass ejections send bursts of energetic charged particles out through solar system. charged particles streaming from sun can disrupt electrical power grid and can disable communications satellites. if earth is in path of coronal mass ejection, we get an aurora.
154
Most luminous stars are ____ Lsun
10^6
155
Least luminous stars are _____ Lsun
10^-4
156
laws of thermal radiation
hotter objects emit more light at all wavelengths and emit light at shorter wavelength and higher frequencies
157
To find temperature of stars
1) use spectroscopy 2) color (photometry) 3) level of ionization from absorption lines in the spectrum
158
Most of the brightest stars are ___
red
159
Why are some red stars so much more luminous
they are bigger. biggest are 1000 R sun, smallest are 0.1 Rsun
160
Newtons version of keplers third law
know the formula
161
Visual Binary
we can directly observe the orbital motions
162
Eclipsing Binary
we can measure periodic eclipses
163
Spectroscopic Binary
We determine orbit by measuring doppler shifts
164
To measure mass, we need 2 of 3 observables
orbital period, radius or orbital separation, orbital velocity. for circular orbits, v = circumference/p
165
Most massive stars are ____ M sun
100
166
Least Massive stars are ___ M sun
0.08
167
Radius measured from ___ and ___
T and L. R is proportional to sqrt (L/T^4)
168
stellar luminosity classes
1 supergiants, 2 bright giants, 3 giants 4 subgiants 5 main sequence
169
Properties of stars depends on ___ and ___
mass, age
170
High mass stars on the main sequence have
High luminosity, short lives, large radius, blue. because core pressure and temperature have to be larger to balance gravity, leading to higher fusion rate and larger luminosity
171
Low mass stars have on main sequence:
low luminosity, long lives, small radius, red
172
Upper left hand corner of HR
high mass stars, shorter life, more luminous and hot, fewer in number
173
How long do stars live
as long as their fuel supply/fuel consumption rate. related to mass/luminosity of star. on main sequence, Mass is amount of fuel. luminosity describes how fast it's consumed. M^-2.5
174
Every M dwarf that was every created is still on the main sequence because the universe is
10^10 years old
175
Mass and Lifetime
Life expectancy of 10 M sun star: 10 times as much fuel, and uses it 10^4 as fast. L is proportional to Mass^3.5. so 10 billion x 10/10^4 = 10 million. 0.1 M sun star can live 100 billion years
176
Open clusters
100s of stars, 10^6-9 years old, irregular shapes, gas or nebulosity
177
Clusters are useful for
studying stellar evolution. all stars are the same distance, use apparent brightness. all formed about the same time and have the same age.
178
Turnoff Point
Main Sequence TP of a cluster tell us its age. all stars arrived on MS at the same time. the cluster is as old as the most luminous/massive star on left of the MS. All MS ars to the left have used up their H fuel are are gone. The position on the hottest brightest star on a cluster's main sequence is the MS turnoff point.
179
Stars die in this order
massive blue, white, yellow, orange, red
180
Older clusters have ___ main sequences
shorter
181
protostar contracts and heats and until core temp is sufficient for hydrogen fusion.
contraction ends when energy released by the fusion balances energy radiation from surface. takes 50 millions years for SUN
182
Mass of protostar determines
how long protostar phase will last. where the newborn star will last on MS. mass determines structure of star
183
Star more massive than 100 M SUN would
blow apart
184
Star less massive than 0.08 M Sun
cant sustain fusion. degeneracy pressure stops gravitational contraction before fusion can begin (prohibits two electrons from occupying same state in same place)
185
Protostar with mass less than 0.08 M Sun is called a ___ ___
brown dwarf. very faint, emit infrared with cores of hydrogen. degenerate cores. has thermal energy. cools off after degeneracy pressure stops contraction.
186
Low mass star is ___ M solar or below
8
187
A star remains on main sequence as long as it can _______
fuse hydrogen into helium in its core
188
When a star can no longer fuse hydrogen into helium in its core, the core
shrinks and heats up
189
Helium fusion into carbon needs higher temp
100 million K as opposed to 10 million K for hydrogen
190
What happens are a star's inert helium core starts to shrink?
Hydrogen fuses in shell around the core
191
The core beings to collapse when leaving the main sequence. describe.
H shell heats up and H fusion begins there. Less gravity from above to balance the pressure. So the outer layers of the star expand. the star is not in subgiant phase. rising fusion rate in the shell does not expand core, so luminosity rises to red giant.
192
In a low mass star when the temperature rises enough for helium fusion to begin,
helium fusion rises sharply because degeneracy pressure is the main form of pressure in the inert helium core. helium fusion increases until thermal pressure takes over and expands core again.
193
Horizontal branch stars
h burning shell and he burning core
194
When helium runs out in the core
helium fusion begins in the shell
195
Asymptotic giant branch
He and H burning shell and degenerate c core
196
Chandrasekhar limit
1.4 solar mass. the most massive a white dwarf can be. at that point, its size drops to zero.
197
cno cycle
fuse h into helium. more efficient at higher temp
198
after main sequence in massive stars, massive stars
burn well past carbon, until it has an inner core of iron. iron is the most stable element and cannot partake in fusion reactions. C is exhausted and core collapses until O fuses. O Ne Mg Si Fe
199
high mass stars become __ after core H runs out
super giants. luminosity doesnt change but radius gets larger.
200
Fe core continues to collapse until it is stopped by
electron degeneracy
201
As the shells of fusion around the core increase in number,
thermal pressure overbalances lower gravity in the outer layers, surface of star expands and cools, becomes red supergiant. for the most massive stars, core evolves too quickly and outer layers explode before even becoming supergiant
202
What are jovian planets like on the inside
no solid surface, layers under high pressure and temperature. cores made of hydrogen compounds, metals and rock. the layers are different for different planets because of difference in size, gravity, compression
203
Physical states of cores of the less massive jovians are
less extreme
204
Jovian planets have strong magnetic fields
high interior temp and churning of hot gases
205
Jovian planets have large, strong storms
rotation speed of Jupiter high
206
Great Red Spot
wind force.
207
What kinds of moons orbit jovian planets
medium and large moons formed at same time as their planets. small moons are captured asteroids and comets. many moons, more than 100 jovian moons. 60+ moons of jupiter
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Large moons
enough self gravity to be spherical. are/were geologically active. icy. formed in orbit around jovian planets. circular, equitorial orbits in same direction as planet rotation.
209
Small moons
potato shaped because not enough gravity. captured asteroids, so orbits do not follow patterns
210
Jupiter's moons
unusual because Io has volcanoes. Europa has ocean under ice. Ganymeade and Callisto has subsurface oceans
211
Saturn's rings
made up of many tiny little pieces that orbit over Saturn's equator. very thin.
212
Why do they have rings
formed from dust created in impacts on moons orbiting these planets. they all have a lot of small moons close in
213
how do we know why they have rings
not leftover from planet formation, so there must be a continuous replacement
214
tides
1. Tides have resulted in the tidal locking of most of the
planetary satellites: their spin periods are the same as
their orbital periods
2. Tides between moons can heat the moons, even to the
point of melting their interiors
3. Tides create patterns in the orbits of rings
4. Tides create patterns in the orbits of astero
215
asteroids live in the asteroid belt ____ AU
2-3. 10^5 asteroids bigger than a few meters in size
216
asteroid orbits are more __ than planetary
elliptical and inclined
217
Trojan asteroids
share jupiter's orbit
218
near earth asteroids
cross earth's orbit
219
asteroid belt
kirkwood gaps created orbital resonances. tugs from jupiter's gravity prevented them from accreting into planet.
220
meteorites
primitive older or processed, matter has differentiated and fragments of a larger object which had original solar nebula material
221
primitive
stony or carbon rich
222
processed
metallic or rocky
223
comets
dirty snowballs of nucleus.usually dont have tails. usually frozen in outer solar system. when they enter inner solar system, they can grow tails, subliminating into gas and carrying off dust
224
oort cloud and comets
random orbits extending to 50,000 AU
225
kuiper belt and comets
orderly orbits 30-100 AU, same direction and planet as planets
226
Pluto
pluto closer to sun than neptune. not a gas giant like the other outer planets. very elliptical orbit. very small. large moon.thin nitrogen atmosphere
227
planets, dwarf planets and small solar system bodies
what our ss is made of
228
wobble
caused by planet gravitationally tugging the star . looking for period motion of the stars they orbit. measure through doppler shift of the star's spectrum
229
___ of wobble tell us ___.
size, mass. period, radius of orbit
230
detect planets if they __ their star
eclipse
231
extrasolar planets how many
180, more massive to jupiter, closer to their star than earth is to sun.
232
asteroid orbits are more __ than planetary
elliptical and inclined
233
Trojan asteroids
share jupiter's orbit
234
near earth asteroids
cross earth's orbit
235
asteroid belt
kirkwood gaps created orbital resonances. tugs from jupiter's gravity prevented them from accreting into planet.
236
meteorites
primitive older or processed, matter has differentiated and fragments of a larger object which had original solar nebula material
237
primitive
stony or carbon rich
238
processed
metallic or rocky
239
comets
dirty snowballs of nucleus.usually dont have tails. usually frozen in outer solar system. when they enter inner solar system, they can grow tails, subliminating into gas and carrying off dust
240
oort cloud and comets
random orbits extending to 50,000 AU
241
kuiper belt and comets
orderly orbits 30-100 AU, same direction and planet as planets
242
Pluto
pluto closer to sun than neptune. not a gas giant like the other outer planets. very elliptical orbit. very small. large moon.thin nitrogen atmosphere
243
planets, dwarf planets and small solar system bodies
what our ss is made of
244
wobble
caused by planet gravitationally tugging the star . looking for period motion of the stars they orbit. measure through doppler shift of the star's spectrum
245
___ of wobble tell us ___.
size, mass. period, radius of orbit
246
detect planets if they __ their star
eclipse
247
extrasolar planets how many
180, more massive to jupiter, closer to their star than earth is to sun.
