The Galaxies

1
The Galaxies
2
Description

• Size
• From 107 to 1012 stars
• From from 1000 to 100000 parsecs
• 1 parsec 3,262 light years
• Number
• More than 1011

3
History of observation

• End of the 18th century Messier - Herschel
• 1845 Lord Rosse
• 1923 Hubble

4
Types

• Spiral
• Barred spiral
• Elliptical
• Irregular

5
Dynamics and Activities

• Interactions
• - Near misses
• - Collision
• - Merger
• Starburst
• Active galaxies

6
Formation and Evolution

• - Just after big bang rapid expansion of the
  universe
• - 300000 years after Big Bang first structures
• - 2 billion years after the Big Bang
  protogalaxies
• - 4 billion years after the Big Bang mature
  galaxies

7
Larger and smaller scale structures