Astrophysics final – Flashcards
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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= 5x10^13 g/cm3, temp= 1x10^12 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 = 9x10^-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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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)
