GALAXIESGALAXIES

Pages 639-642Pages 639-642

GalaxiesGalaxies

Def: large scale groups of stars (approx. Def: large scale groups of stars (approx. 100 billion) bound by gravitational 100 billion) bound by gravitational attraction- rotates around a centerattraction- rotates around a center

Also contain nebulae, planets, dark matter Also contain nebulae, planets, dark matter (90%), space, etc..(90%), space, etc..

Is the center of every galaxy a Is the center of every galaxy a supermassive black hole?supermassive black hole?

Small Magellanic Cloud

Nearest galaxy 150,000 lyNearest galaxy 150,000 ly

Andromeda (M31)Andromeda (M31)

A large galaxy neighborA large galaxy neighbor2,900,000 ly2,900,000 ly

Milky WayMilky Way

• StructureStructure• Barred spiral galaxy Barred spiral galaxy

• About 100,000 About 100,000 light-years widelight-years wide

• Sun is 30,000 light-Sun is 30,000 light-years from the center years from the center

• Rotates every 200 Rotates every 200 million years around million years around “galactic center”“galactic center”

Milky WayMilky Way

Face-on view of the Face-on view of the Milk Way GalaxyMilk Way Galaxy

Edge-on view of the Edge-on view of the Milk Way GalaxyMilk Way Galaxy

Galaxy SongGalaxy Songfrom Monty Pythonfrom Monty Python

http://www.youtube.com/watch?v=vIy76M-4txo&feature=related&safety_mode=true&persist_safety_mode=1&safe=active

Types of GalaxiesTypes of Galaxies

M105

NGC 3384

Elliptical galaxyElliptical galaxy

60% of all galaxies60% of all galaxiesContain older starsContain older starssmallsmall

LMC

Large Magellanic cloud

NCG 6946

Spiral galaxiesSpiral galaxies

30% of all galaxies30% of all galaxiesOlder in center; younger in armsOlder in center; younger in arms

A barred spiral galaxyA barred spiral galaxy

Merger of two Spirals to form an Elliptical

Irregular galaxyIrregular galaxy

10% of all galaxies10% of all galaxiesContain young starsContain young stars

M104 (The Sombrero Galaxy)

Hubble’s LawHubble’s Law

Galaxies are receding at a speed Galaxies are receding at a speed proportional to their distanceproportional to their distance

Farther galaxies are moving faster than Farther galaxies are moving faster than nearby galaxiesnearby galaxies

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

Raisin bread analogy of an Raisin bread analogy of an expanding universeexpanding universe

What would cause this?What would cause this?

EXPANDING EXPANDING UNIVERSE!UNIVERSE!

Cosmological red Cosmological red shift- supports thisshift- supports this

Local groupLocal group

Local Group Local Group • Milky way and nearest Milky way and nearest

galaxiesgalaxies• Contains at least 28 Contains at least 28

galaxiesgalaxies

What pattern do galaxies form What pattern do galaxies form in the universe?in the universe?

AMAZING FACTAMAZING FACT

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

What is your galactic addressWhat is your galactic address

Power of TenPower of Ten

http://micro.magnet.fsu.edu/primer/java/http://micro.magnet.fsu.edu/primer/java/scienceopticsu/powersof10/index.htmlscienceopticsu/powersof10/index.html