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Stars Galaxies and the Universe
Introduction : The Big Picture
Hierarchy of structures:
• Nuclei (particles)
• Atoms
• Stars/Planets
• Galaxies
• Universe
Atoms:
Nuclei:
protons
neutrons
Electrons
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
Earth
Sun
Earth orbit
Solar system
Nearest star
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100 nm
10 μm
¼ cm
20 cm
250 m
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virus
cell
pin head
saucer
lawn
Jewel Box
Cluster
Naked eye
stars
Eagle
Nebula
Galaxy Center
Crab
Nebula
Solar system
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
Interacting
galaxies
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
SDSS : ⅓ million galaxies
Our galaxy is here
Hubble Deep Field
~1500 galaxies
Sky area ~2.5×2.5 arcmin
≡ pinhead @ arms-length
A 1689
Rich galaxy cluster
2 Gly distant
Gravitational lens
13.7 Gly
The Visible Universe
MW galaxy
Local group
Virgo cluster
Coma cluster
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20 m
600 m
15 km
100 km
Keck/VLT
+ Cluster Lens
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0
class room
central grounds
Walmart
Culpeper
SDSS &
2dFGRS
“Nearby”
galaxies
HDF
Our Galaxy