Summary of physical laws for astronomy

Units of measurement.

Important numbers:

• Temperature of Sun at photosphere: 6000 K.
• Speed of light: 3 x 10⁸ m/s.
• Astronomical unit: 1.5 x 10¹¹ m.
• Light year: 10¹⁶ m.
• Distance to center of the Galaxy: 25 kly.
• Distance to Andromeda Galaxy: 2 Mly.
• Age of the universe (from Hubble Law), roughly 10 x 10⁹ y.

Laws:

• Distance d an object goes if it moves for time t at speed v.
  
• Wavelength and frequency of light.
  
• Energy of a single photon
  
• Energy conservation
  
  
• Determining the distance to a ``standard candle'' from its known luminosity and its apparent brightness
  
• Determining the mass of a source of gravity from the speed of a lighter object in a circular orbit around it.

• The Hubble Law relating distance and speed of recession of distant galaxies.