Astrophysics final

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milky way galaxy
– 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
– 1st resolved milky way into stars
– telescope
william and caroline herschel
– 1st to map milky way
– night sky; 4,000 objects other than stars
distances by cepheid variable stars
– in milky way
– standard distant candle, changes brightness/time
– higher luminosity over time, use inverse square distance
– some cepheid variable stars are binary
distance indicators
1. cepheid variable stars
2. distribution of open star clusters
disk component
– 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
spherical components
1. Nuclear Bulge; dense sphere of older stars, radius is 6,520 LY
2. Halo; spherical cloud of low density stars, globular clusters
age of milky way
– open star cluster distribution, 9-10 billion years
– globular cluster distribution, 11 billion years
– distribution of clusters and shape, 13 billion years
stellar population I stars
– star in disk and spiral arms
– rich in metals; 2.3% metals
– circular orbits around galactic center
– young, bluer, ISM
stellar population II stars
– stars in nuclear bulge, halo
– lean in metals, only H and HE
– older, original stars, 11-12 billion years old
– spherical orbits
formation of milky way galaxy (traditional hypothesis)
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
shape of galaxy
– 3 spiral arm galaxy; Sagittarius, Perseus, Onion-Cygnus
– radio astronomy; 4-5 spiral arms
– recent research; 2 arm galaxy, barred galaxy
density wave theory
– one spiral arm will overtake the other
– produces star formation; 1,000s of new stars
– see new star formation on edges of spiral arms
center of the milky way
– Sagittarius
– massive black hole
– 2.6 x 10^6 solar masses
– study of the structure and evolution of the universe as a whole
– infinity; becoming larger without end
– universe is finite
– universe has a beginning
boundaries in our world
– 3-D
– time
universe is unbounded
– no outward edge
– no center
Heinrich Obler
– austria
– infinite universe; stars fill up the sky
Edgar Allen Poe
– universe was formed at one point of time
– most distant light hasn’t reached us yet
– past that point of formation; entirely dark
– 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
Edwin Hubble
– 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
Hubble law
– galaxy’s red shift is proportional to distance
– galaxies are receding from each other
– hubbles constant 70 km/sec/mpc
big bang
– 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
Arno Penzios and Robert Wilson
– 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
– property of being uniform
– property of being same in all directions
cosmological principle
– universe is isotropy and homogeneity
shape of universe
– galaxies have low velocities
– space is the media on which galaxies are along for the ride
– space is expanding
holding galaxies together
– gravity
– dark matter/energy
percent of baryonic/non baryonic matter
– 5% baryonic matter; all known matter
– 95% non baryonic matter; dark matter/gravity/energy
four fundamental forces
1. gravity
2. electromagnetic force
3. strong force; bonding of atoms
4. weak force; radioactive decay
grand unified theory
– joining all four forces into one mathematical statement
best model of the universe
– 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
– 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
physical evidence of multiverses
black hole cosmological model
– gravity =infinity
– density =infinity
– R =0
– black whole (normal space/time) ->point of singularity-> white hole (opposite space/time)
Categories: Astrophysics