Galactic Census

This is taken from the 1978 edition of Cambridge Encyclopedia of Astronomy
(pg. 313, to be precise).

Gross inventory of our Galaxy

Stars

  • Total number: 1011(I’ve heard 200 billion elsewhere)
  • Binary or multiple: 70%
  • White dwarfs: 15%
  • Spectral class O-B: 11%(really?)
  • Spectral class A-F: 41%
  • Spectral class G, K and M: 48%

Other objects

  • Planetary nebulae: 700 known
  • Globular clusters(106 stars average): 18,000
  • Novae: 2.2 per year on average
  • Supernovae: 1 per 50 years on average
  • Supernova remnants: ~1000
  • Pulsars: 160 known

Mass: 1.4 x 1011 Solar mass
Color: Yellowish, similar to a G2 star
Absolute magnitude: -20.5 mag
Radius: 25,000 PC(Sun is at 10,000 PC from the center)
Rotational speed: 200 km/sec in Sun’s vicinity
Thickness

  • Stellar disk: 1,000 PC
  • Gaseous disk: 100PC

Distance between stars: 1 PC on average in vicinity of Sun

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