Astrophysics final

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milky way galaxy
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– one out of billions/trillions – named by the greeks; galaxies kuklos, milky circle – Romans; via lactea= milky way – andromeda (closest galaxy to us) 2.3 million LY away – 400 billion solar masses
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galileo
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– 1st resolved milky way into stars – telescope
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william and caroline herschel
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– 1st to map milky way – night sky; 4,000 objects other than stars
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distances by cepheid variable stars
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– in milky way – standard distant candle, changes brightness/time – higher luminosity over time, use inverse square distance – some cepheid variable stars are binary
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distance indicators
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1. cepheid variable stars 2. distribution of open star clusters
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disk component
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– matter in rotation – stars, star clusters, gas/dust – spiral arms – blue, hotter, newer stars – 300 LY thick – solar system 27,710 LY from galactic center
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spherical components
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1. Nuclear Bulge; dense sphere of older stars, radius is 6,520 LY 2. Halo; spherical cloud of low density stars, globular clusters
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age of milky way
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– open star cluster distribution, 9-10 billion years – globular cluster distribution, 11 billion years – distribution of clusters and shape, 13 billion years
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stellar population I stars
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– star in disk and spiral arms – rich in metals; 2.3% metals – circular orbits around galactic center – young, bluer, ISM
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stellar population II stars
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– stars in nuclear bulge, halo – lean in metals, only H and HE – older, original stars, 11-12 billion years old – spherical orbits
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formation of milky way galaxy (traditional hypothesis)
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1. spherical cloud of ISM gas/dust 2. gravity pulls ISM- rotation 3. globular clusters form, remained in halo 4. further contraction/rotation- disk 5. gas/dust collects in disk 6. newer stars form in disk; giant, supergiant, supernova-metals
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shape of galaxy
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– 3 spiral arm galaxy; Sagittarius, Perseus, Onion-Cygnus – radio astronomy; 4-5 spiral arms – recent research; 2 arm galaxy, barred galaxy
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density wave theory
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– one spiral arm will overtake the other – produces star formation; 1,000s of new stars – see new star formation on edges of spiral arms
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center of the milky way
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– Sagittarius – massive black hole – 2.6 x 10^6 solar masses
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cosmology
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– study of the structure and evolution of the universe as a whole – infinity; becoming larger without end – universe is finite – universe has a beginning
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boundaries in our world
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– 3-D – time
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universe is unbounded
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– no outward edge – no center
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Heinrich Obler
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– austria – infinite universe; stars fill up the sky
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Edgar Allen Poe
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– universe was formed at one point of time – most distant light hasn’t reached us yet – past that point of formation; entirely dark
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universe
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– does have a beginning; the big bang 13.8 billion years ago – oldest known galaxy formed 1 billion years ago – singularity of time and space
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Edwin Hubble
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– categorized galaxies by their shape – learn chemistry of galaxies by spectrum – learned that all galaxies are shifter towards red; red shift – galaxies are receding from our point of view
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Hubble law
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– galaxy’s red shift is proportional to distance – galaxies are receding from each other – hubbles constant 70 km/sec/mpc
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big bang
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– hubbles law – implies all galaxies emerged from a moment if time – implies that all had a beginning; singularity – 14 billion years ago – at beginning density= 5×10^13 g/cm3, temp= 1×10^12 K
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Arno Penzios and Robert Wilson
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– bell labs – microwave receiver 1959; received microwave noise – 1964 discovered the remnant microwave radiation from big bang – nobel prize – brings together various energies left over from big bang
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homogeneity
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– property of being uniform
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isotropy
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– property of being same in all directions
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cosmological principle
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– universe is isotropy and homogeneity
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shape of universe
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– galaxies have low velocities – space is the media on which galaxies are along for the ride – space is expanding
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holding galaxies together
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– gravity – dark matter/energy
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percent of baryonic/non baryonic matter
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– 5% baryonic matter; all known matter – 95% non baryonic matter; dark matter/gravity/energy
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four fundamental forces
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1. gravity 2. electromagnetic force 3. strong force; bonding of atoms 4. weak force; radioactive decay
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grand unified theory
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– joining all four forces into one mathematical statement
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best model of the universe
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– flat; open, infinite universe – CD = 9×10^-30 g/cm3 – expansion will slow down with time – star formation will slow down – galaxies will be dark
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multiverses
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– hypothetical set of infinite/finite universes including our galaxy – they compose everything; space/time, matter, energy – parallel universe – dimensional planes – alternate universe – quantum universe – 1st reference by Erwin Schrodinger
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physical evidence of multiverses
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black hole cosmological model
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– gravity =infinity – density =infinity – R =0 – black whole (normal space/time) ->point of singularity-> white hole (opposite space/time)

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