GALAXIES Pages 639-642

Galaxies Def: large scale groups of stars (approx. 100 billion) bound by gravitational attraction Also contain nebulae and solar systems

Milky Way Structure Barred spiral galaxy About 100,000 light-years wide Sun is 30,000 light-years from the center Rotates every 200 million years around “galactic center”

Milky Way

Face-on view of the Milk Way Galaxy

Edge-on view of the Milk Way Galaxy

Andromeda (M31) A large galaxy neighbor 2,900,000 ly

Elliptical(60%)- old stars Irregular (10%)- young stars Types of Galaxies Spiral (30%) Barred Spiral Elliptical(60%)- old stars Irregular (10%)- young stars

NCG 6946

A barred spiral galaxy

Elliptical galaxy

Irregular galaxy

Nearest galaxy 150,000 ly Small Magellanic Cloud

Large Magellanic cloud LMC

M104 (The Sombrero Galaxy)

Hubble’s Law Galaxies are receding at a speed proportional to their distance Farther galaxies are moving faster than nearby galaxies

http://hyperphysics.phy-astr.gsu.edu/hbase/astro/hubble.html#c3

Raisin bread analogy of an expanding universe

What would cause this? EXPANDING UNIVERSE! Cosmological red shift- supports this

Is the center of every galaxy a supermassive black hole?

Chandra image Jan. 2008 Centaurus A Evidence of spinning

NGC 3384 M105

Hubble deep field

Merger of two Spirals to form an Elliptical

Colliding galaxies movie http://wps.prenhall.com/wps/media/objects/680/696364/ifa_colliding_galaxies.mpg

Local group Local Group Milky way and nearest galaxies Contains at least 28 galaxies

AMAZING FACT Our known Universe contains at least 1,000,000 billions ( Thats One Million, Billions) of other Galaxies...like our own Milky Way. There is no doubt that there are other vast Universes in existence on top of our Universe

LARGEST TO SMALLEST UNIVERSE LOCAL GROUPS GALAXIES SOLAR SYTEMS

Power of Ten http://micro.magnet.fsu.edu/primer/java/scienceopticsu/powersof10/index.html

Galaxy Song from Monty Python http://www.youtube.com/watch?v=Z2JU4gX6rg8