PHYS 005 Study Guide - Midterm Guide: Galactic Center, Cygnus A, Relativistic Speed
5 Jul 2018
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5/21 Session 22 Midterm Review
Hubble Law
Velocity that objects are moving away fr us given their DISTANCE
●Hubble constant H0= 71 km/mpc*s
●d= Distance to galaxy
○v=H0*d
■The further galaxies are from us, faster they are moving away (exponentially
accelerating velocity)
●**if you are closer to us, you are moving closer to us
Redshift
●Expected color- things if they were not moving away from us
●Observed color- things as they actually are
○UNITLESS
●We are looking @ it as it was in the past
○Z +1
■Density, distance, temperature
●Density- (z+1)^3
●Distance- z+1
●Temperature- current T*(z+1)
■Matters more for smaller numbers
Redshift = LookBack Time depends on several things
●Amount of matter
●Curvature of universe
●Hubble Constant H0
●Amount of dark energy
Galactic Clusters
●Poor cluster
○Milky Way, Andromeda, Triangulum, Large & Small Magellanic Clouds
○Few galaxies- 40 galaxies
■dwarf/spherodal galaxies
Galacatic Cannibalism
●Gravity from the bigger galaxies pull in the smaller ones
●Rich Cluster
○Virgo Cluster
○2000 galaxies
■Distance determined w. Cepheid stars & Tuller-Fisher relationship
Superclusters of Galaxies
** NOT the same as rich clusters
●100,000 galaxies
●Lanikea supercluster
●520,000 ly across
●Great Attractor- center of mass in supercluster
Large-Scale Structure of Universe
●Nodes
○where filaments merge together
○Where you find clusters of galaxies
●Filaments
○Have matter, like strands
○Feed NODES
●Voids
○Empty bubbles
Colliding Galaxies
●Occur due to gravity in universe
●Merges close gravities together
○STARS do not collide
○Gas & dust collides
■If gas collide & create friction- creates stars
●Hot gas- emits x-rays
○Needs cooler gas to creates stars
Flybys may be 3rd way to create spiral arms
●Usually results in collision
○Stars form in COLDER gas collision sites
Starburst Galaxies
●HUGE amount of new stars are created thru colliding galaxies
2 spirals collapsing -> elliptical
●Ellipticals usually have pop 2 stars
Andromeda & MW colliding??
●In 4 billion years
Dark Matter
Document Summary
Velocity that objects are moving away fr us given their distance. The further galaxies are from us , faster they are moving away (exponentially accelerating velocity) **if you are closer to us, you are moving closer to us. Expected color- things if they were not moving away from us. Observed color- things as they actually are. We are looking @ it as it was in the past. Redshift = lookback time depends on several things. Milky way, andromeda, triangulum, large & small magellanic clouds. Gravity from the bigger galaxies pull in the smaller ones. Distance determined w. cepheid stars & tuller-fisher relationship. Great attractor- center of mass in supercluster. If gas collide & create friction- creates stars. Flybys may be 3rd way to create spiral arms. Stars form in colder gas collision sites. Huge amount of new stars are created thru colliding galaxies. 90% of matter in galactic superclusters is dark matter.
