Scale of the Universe

1
Scale of the Universe

• How big is stuff?

2
Earth-Moon

• Earth 8k miles in diameter
• Rotates?
• Moon about a ¼ of the Earth size
• Moon is 100 of its diameters away

3
Solar system
Sun
Sizes not to scale!

• Earth-Sun distance is the astronomical Unit
  (AU)
• Planets at 0.4, 0.7, 1 (us!), 1.5, 5, 10, 20, 40
  Aus, and

4
New planet 7/31/05

• 96 AUs
• Really a Kuiper Belt object?
• Orbit inclined 45O

5
Nearest Star

• 4.2 light years (ly) away
• c 3 x 105 km/s
• 1 ly 9.5 x 1012 km or about 63,000 AU
• So nearest star is 4.2 times this or about
  265,000 AUs

6
Our Milky Way Galaxy

• MWG about 100,000 ly in diameter
• We are 2/3 the way out

7
Nearest Galaxy, in Andromeda

• 2 million light years away
• (about 20 MWG diameters)

8
The Local Group

• A few dozen galaxies
• Spread over a few Mly

9
Nearest Large Group

• Virgo Cluster 60 Mly away (20 LG dias)
• 1000 member galaxies in it

10
Observable Universe 14.7 Gly

• Hubble Deep Field