The UniverseCh. 20

d. universe: the sum of all space, matter & energy for all time (past, present, & future) http://www.youtube.com/watch?v=J9XVEg

NOHZEMostly empty space!

What is the universe?

It all started in a small, concentrated place

~13.8 billion years agoHas been expanding ever since

Gravity clumped thing togetherWhat was formed from those clumps of cosmic stuff?

Big Bang TheoryBANG!

d. star: ball of gas that emits (gives off) EMR (electromagnetic radiation)driven by nuclear fusionhydrogen nuclei combined into helium

HUGE energy output

What is a star?

Classified by sizeSupergiant (Rigel, Betelgeuse)

GiantMedium-sized (Sun)White dwarfNeutron (16 km; about the size of Manhattan island)

Elements…but how do we know which ones?

ColorIndicates temp of star (NOT size!)

R O Y G B I VCooler to hotter

What are they made of?

Spectroscope tool to see light spectra (“rainbows”)

Spectral lines – each element gives off different pattern of colored lightEach pattern is unique to a specific element

What’s out there?Mostly empty spaceSuperclustersClustersGalaxiesStarsPlanets & stellar systems

Gas, dust, smaller stuff

BIG

little

d. cluster: a group of stars & galaxies bound by gravityLocal group

Milky Way galaxy (ours!)

Andromeda galaxy (closest to us)

Hercules cluster (p. 675)

SNICKERS

d. galaxy: a collection of stars, gas, & dust held together by gravityMillions or billions of stars

So far away that we can’t see individual stellar systemsNewer galaxies appear bluish

Older galaxies appear reddish

Classified by shapeSpiralElliptical (not quite circular)

Irregular Messier 74

Great Barred