Stars Galaxies and the Universe

Introduction : The Big Picture

Hierarchy of structures:• Nuclei (particles)• Atoms• Stars/Planets• Galaxies• Universe

Atoms:Nuclei:

protonsneutronsElectrons

p.418a

Solar magnetic surface storm

Earth

Scale of the Solar System

• Earth-moon system…..• The sun as an orange….• The nearest star• The galaxy !

Our Galaxy : The Milky Way

Milky way galaxy is a complex system• 1011 stars (& planets?)

Each with life cycle: birth/life/death• Material between the stars

Tenuous gas: clouds; diffuse

New star-formation region

Two young star clusters

Slow death of low mass star

Our Galaxy

Solar systemGalaxy Center

Earth = 100 nm = virusSun = 10 μm = cellEarth orbit = ¼ cm = pin headSolar system = 20 cm = saucerNearest star = 250 m = lawn

Naked eyestars

EagleNebula

Jewel BoxCluster

CrabNebula

The Population of Galaxies

Galaxies are a diverse population• Different sizes & shapes & motions

different histories?• They tend to form groups

pairs clusters; some collide and merge

Interactinggalaxies

Galaxies to the horizon

The Universe is filled with galaxies• 1011 galaxies visible• More distant ones appear younger

look-back time due to finite light speed

Our galaxy is here

3 billion light years

(~20% to “the edge”)

SDSS : ⅓ million galaxies

Hubble Deep Field~1500 galaxies

Sky area ~2.5×2.5 arcmin≡ pinhead @ arms-length

A 1689Rich galaxy cluster

2 Gly distantGravitational lens

The Visible Universe

HDF

SDSS &2dFGRS

“Nearby”galaxies

13.7 Gly 0

MW galaxy = 20 m = class roomMW galaxy = 20 m = class roomLocal group = 600 m = central groundsVirgo cluster = 15 km = WalmartComa cluster = 100 km = Culpeper

Our Galaxy

Keck/VLT+ Cluster Lens