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67 Cards in this Set
- Front
- Back
*_______ our ONLY source of info for distant objects (the broader universe) *an electromagnetic wave, but also behaves like a particle |
light |
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wavelenght=repeat distance frequency=# of repeated occurence/time wavelength x frequency= speed of light [c=300,000 km/s (in a vacuum)] |
wave properties |
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*visible light makes up a small fraction of all light, types of light vary by wavelenght (ex. X-rays, gamma rays, radio waves, etc) |
the electromagnetic spectrum |
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*emission (object emits light) *absorption (light gets absorbed) *transmission (light moves through matter) *reflection/scattering (what we see) |
ways that light interacts with matter |
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*"why is the sky blue" *our atmosphere scatters the visible light *gases in our atmosphere scatter light with shorter wavelenghts (blue) most effectively |
interactions between light and matter determine the appearance of everything around us |
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*the light from an object passed through a prism to separate the light into all the various wavelenghts, some are visible |
spectrum |
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*each element has a unique spectral fingerprint which is expressed as emission and absorption lines in an objects spectrum |
chemical composition (info that can be determined by light) |
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*as an object's temperature increases, the object radiates light more strongly at shorter wavelengths |
temperature (info that can be determined by light) |
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*(towards or away from you) the Doppler effect, we generally measure the doppler effect from shifts in the wavelengths of spectral lines |
Doppler Motion (info that can be determined by light) |
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*longer wavelengths of visible light, object is moving away from you |
red shift |
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*shorter wavelengths of visible light, object is moving towards you |
blue shift |
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*tells us ONLY about the part of an object's motion toward or away from us |
Doppler shift |
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*a _______ is the distance that light can travel in one year |
light year |
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*because of the amount of time it takes for light to reach us, the farther we look out in distance, the further we look back in time. *we cannot see more than 14 billion light years, because we would be looking back to before the universe was formed |
light year |
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*collect more light than our eyes>light-collecting area *see more detail than our eyes>angular resolution |
telescopes |
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refracting: lenses used to concentrate light reflecting: mirrors used to concentrate light |
basic optical telescope design |
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*it is not because they are effectively closer to the stars -light pollution -turbulence of the atmosphere causing "twinkling stars" -our atmosphere absorbs most of electromagnetic spectrum, including all UV and X ray and most infrared |
why do we put telescopes into space? |
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* a star, & it is our best proxy for other stars because we can easily study it E=mc2 *shines not because it is on fire, but because it is powered by nuclear energy fusion |
the sun |
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*energy provided by fusion maintains the outward pressure that stops the star from collapsing in on itself |
gravitational equilibrium |
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*decline in core temperature causes fusion rate to drop, so core contracts and heats up. *rise in core temperature causes fusion rate to rise, so core expands and cools down |
gravitational equilibrium acts as solar thermostat |
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* a flow of charged particles from the surface of the sun |
solar wind (sun structure) |
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*outermost layer of solar atmosphere |
corona (sun structure) |
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*middle layer of solar atmosphere |
photosphere (sun sturcture) |
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*energy transported upward by rising hot gas |
convection zone (sun structure) |
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*energy transported upward by photons |
radiation zone (sun structure) |
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*energy generated by nuclear fusion~15 million K |
core (sun structure) |
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* related to magentic fields in the sun and can impact climate on earth *sunspots *solar flares *solar prominences *coronal mass ejections send burst of energetic charged particles out through the solar system |
solar activity |
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*radius: 6.9 x 108 m *mass: 2 x 1030 kg *luminosity: 3.8 x 1026 watts *surface temperature: 5830 K |
properties of other stars are compared to our stars |
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*we primarily classify stars by their luminosity and temperature, but the most important property of stars is mass |
stellar classification |
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Luminosity: amount of power a star radiates apparent brightness: amount of starlight that reaches earth |
luminosity vs apparent brightness |
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* the relationship between apparent brightness and luminosity depends on distance |
calculating distance |
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*we determine some distances by _______ |
stellar parallax |
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* we estimate star temperature by the color amd spectral type. *color and spectral type: lines in a star's spectrum correspond to a spectral type that reveals its temperature *(hottest) O B A F G K M (coolest) *star temperature range: 3000-50,000 K |
temperature |
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* we measure mass using Newton's version of Kepler's 3rd law as long as we have 2 objects *a3=p2 *M1+M2=A3/p2 |
mass |
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* hertzsprung-russell diagrams plot the luminosities against the spectral types of stars *90% of stars fall on the main sequence of the H-R diagram |
main sequence |
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*a large nebula can make a whole cluster of stars. random motions cause the nebula to contract. the nebula heats up as gravity causes it to contract due to conservation of energy |
gravitational collapse of a nebula (step 1) (life stages of star) |
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*rotation also causes jets of matter to shoot out along the rotation axis |
protostar jet formation (step 1) (life stages of star) |
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* a protostar contracts and heats until the core temperature is sufficient for hydrogen fusion, and then shrinking stops. New star achieves long-lasting state of balance because thee outwards force of fusion matches the inwards collapse of gravity. main-sequence stars are fusing hydrogen into helium in their core, like the sun |
collapse stops when fusion starts (step 1) (life stages of stars) |
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*if fusion never starts...star-like objects not massive enough to start fusion are brown dwarfs |
collapse stops when fusion starts (step 1) (life stages of stars) |
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* a stars's lifetime is dependent on mass because mass determines core temperature |
lifespan of stars and fusion (step 2) (lifespan of stars and fusion) |
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*high mass stars use their core hydrogen quickly (~5 million years) *low mass stars use their core hydrogen slowly (~10 billion years) |
high mass vs low mass stars (step 2) (lifespan of stars and fusion) |
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*small nuclei stick together to make a bigger one. (sun stars) high temperatures enable nuclear fusion to happen in the core by overpowering the repulsion between atoms |
fusion (step 2) (lifespan of stars and fusion) |
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*the sun and other low mass stars releases energy by fusing four hydrgen nuclei (4 protons) into one helium nucleus in a process called the proton-proton chain *high mass stars use the CNO cycle instead |
proton-proton chain vs. CNO cycle |
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* a star remains on the main sequence as long as it can fuse hydrogen into helium in its core. *low mass stars convert hydrogen to helium by the proton-proton chain (slowly, ~ 10 billion years) |
main sequence:proton-proton chain (~10 billion years) (life stages of a low mass star) |
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*after core hydrogen is used up: the core contracts, H begins fusing to He in a shell around the core in the first giant phase *a star becomes larger, redder, and more luminous after its time on the main sequence is over |
first red giant phase (life stages of a mass star) |
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*while the shell is fusing hydrgen, the inner core starts to fuse helium in the second giant phase. helium fusion: 3 helium atoms make 1 carbon atom |
second red giant phase (life span of a mass star) |
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*because a low mass star cannot undergo advance fusion of heavier elements, carbon builds up in the core and the star will never regain stability |
instability and collapse (life span of a mass star) |
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* fusion ends with a pulse that ejects the H and He into space as a planetary nebula |
planetary nebula (instability and collapse) |
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*the core left behind becomes a white dwarf *the leftover carbon core of a low mass star, very dense and hot *the "decaying corpse" of a star, will cool off slowly over time |
white dwarf
(instability and collapse) |
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*high-mass main sequence stars fuse H to He at a higher rate using carbon, nitrogen, aond oxygen as catalyst |
main sequence:CNO cycle (life stages of a high mass star) |
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*hydrogen core fusion (main sequence) *helium core fusion (supergiant) |
early life stages of high mass stars are similar to those of low mass stars (life stages of a high mass star) |
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*high core temperatures allow helium to fuse with heavier elements forming Ne, Mg, etc. *core temperature in very high mass stars allow for advance fusion reactions which forms Si, S and elements as heavy as iron. *high mass stars make the elements necessary for life! *we are star stuff -Carl Sagan |
heavier element progression (life span of a star high mass star) |
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*high temp. nuclear fusion proceeds in a series of shells around the cr |
multiple shell fusion |
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*iron is a dead end for fusion because reactions involving iron do not release energy *iron builds up in the core until pressure can n longer resist gravity *the core then suddenly collapses, creating a supernova explosion |
instability and collapse |
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*energy released by the collapse of the core drives outer layers into space and forms elements heavier than iron, such as gold and uranium |
supernova explosions and remnant |
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*heavy interiors inside the remnant form |
black holes and neutron stars |
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*neutrons collapse to the center, forming a neutron star or sometimes a black hole |
supernova explosive |
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*particles cant be in same state in same place according to the laws of quantum physics |
degeneracy pressure |
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*a neutron star is the ball of neutrons left behind by a massive-star supernova *a neutron star is about the same size as a small city, with the mass of a large star |
neutron stars |
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*jocelyn bell noticed pulses of radio emission coming from a single part of the sky *the pulses were coming from a spinning neutron star, a pulsar, that emits wavesn in the direction of its magnetic axis |
pulsars |
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*a _____ is an object whose gravity is so powerful that not even light can escape it * some massive star supernovae can make a black hole of enough mass falls onto the core (degeneracy pressure is exceeded) |
black holes |
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* as far as we know, gravity crushes all the matter into a single point known as |
singularity |
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*the surface of a black hole is the radius at which the escape velocity equals the speed of light (known as the event horizon) * the event horizon of a 3Msun black hole is also about as big as a small city |
event horizon |
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*what we see as gravity is actually the curvature of spacetime *a black hole is like a bottomless pit of spacetime and even light can escape it |
relativity |
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*star orbiting something massivve but invisible *a supermassive black hole *orbits of stars indicate a mass of about 4 million Msun. |
the milky ways galactic center |
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*term coined by fred hoyle 1949 *using the rate of expansion between galaxies, we can calculate that the universe is 14 billion years old *galaxies themselves remain constant due to gravitational forces |
the big bang and the expanding universe |
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* in the beginning... the early universe was unfathomably hot and dense, and composed of only hydrogen and helium |
the big bang and the expanding universe |