Astrophysics (index)

Astronomical Unit

(about 93 million miles)

An Astronomical Unit (AU) is a distance unit meant to convey the distance between the Earth and the Sun, or more specifically the mean between the Earth's orbit's Aphelion and Perihelion. However, it is now fixed at 149597870700 meters, and only considered a general term for the Earth-Sun distance. An AU is equivalent to:

  • about 150 million km.
  • about 93 million miles.
  • 4.848 × 10-6 Parsecs.
  • 1.581 × 10-5 light years.

Some distances in AU:

0.0000026AU distance from Earth to Moon
0.0000047AU diameter of the Sun
5.2AU radius of Jupiter's orbit
30AU radius of Neptune's orbit
276173AU distance to Alpha Centauri
1.6 billion AU distance to Galactic Center
1604 billion AU distance to Andromeda


Referenced by:
HD 80606 b
Spitzer Space Telescope (SST)