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67 Cards in this Set

  • Front
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*_______ our ONLY source of info for distant objects (the broader universe)


*an electromagnetic wave, but also behaves like a particle

light

wavelenght=repeat distance


frequency=# of repeated occurence/time


wavelength x frequency= speed of light [c=300,000 km/s (in a vacuum)]

wave properties



*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

*emission (object emits light)


*absorption (light gets absorbed)


*transmission (light moves through matter)


*reflection/scattering (what we see)

ways that light interacts with matter

*"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

*the light from an object passed through a prism to separate the light into all the various wavelenghts, some are visible

spectrum

*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)

*as an object's temperature increases, the object radiates light more strongly at shorter wavelengths

temperature


(info that can be determined by light)

*(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)

*longer wavelengths of visible light, object is moving away from you

red shift

*shorter wavelengths of visible light, object is moving towards you

blue shift

*tells us ONLY about the part of an object's motion toward or away from us

Doppler shift

*a _______ is the distance that light can travel in one year

light year



*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

*collect more light than our eyes>light-collecting area


*see more detail than our eyes>angular resolution

telescopes



refracting: lenses used to concentrate light


reflecting: mirrors used to concentrate light

basic optical telescope design

*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?



* 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

*energy provided by fusion maintains the outward pressure that stops the star from collapsing in on itself

gravitational equilibrium

*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

* a flow of charged particles from the surface of the sun

solar wind


(sun structure)

*outermost layer of solar atmosphere

corona


(sun structure)

*middle layer of solar atmosphere

photosphere


(sun sturcture)

*energy transported upward by rising hot gas

convection zone


(sun structure)

*energy transported upward by photons

radiation zone


(sun structure)

*energy generated by nuclear fusion~15 million K

core


(sun structure)

* 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

*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

*we primarily classify stars by their luminosity and temperature, but the most important property of stars is mass

stellar classification

Luminosity: amount of power a star radiates


apparent brightness: amount of starlight that reaches earth

luminosity vs apparent brightness

* the relationship between apparent brightness and luminosity depends on distance

calculating distance

*we determine some distances by _______

stellar parallax

* 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

* 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

* 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

*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)



*rotation also causes jets of matter to shoot out along the rotation axis

protostar jet formation


(step 1)


(life stages of star)



* 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)

*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)

* 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)

*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)

*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)

*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

* 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)

*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)

*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)

*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)

* fusion ends with a pulse that ejects the H and He into space as a planetary nebula

planetary nebula


(instability and collapse)

*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)


*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)

*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)

*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)

*high temp. nuclear fusion proceeds in a series of shells around the cr

multiple shell fusion



*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

*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

*heavy interiors inside the remnant form

black holes and neutron stars

*neutrons collapse to the center, forming a neutron star or sometimes a black hole

supernova explosive

*particles cant be in same state in same place according to the laws of quantum physics

degeneracy pressure

*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

*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

*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

* as far as we know, gravity crushes all the matter into a single point known as

singularity

*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

*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

*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

*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

* 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