meter (m) - the fundamental unit of length in the metric system. Equal to about 3.3 feet or 1.1 yard.

kilometer (km) - equal to 1000 meters.

Astronomical Unit (AU) - the commonly used unit of distance in the Solar System; it is equal to the average Earth-Sun distance, or approximately 149,600,000 km.

light year (ly) - a commonly used unit of distance outside the solar system, equal to the length travelled by light in one year. It is equal to 9,460,000,000,000 km.

parsec (pc) - the preferred (by astronomers) unit of distance outside the solar system. Defined as the distance at which 1 Astronomical Unit subtends an angle of 1 second of arc (1/3600 of a degree), or the distance an object has to be for its parallax to equal 1 second of arc. Equal to 3.26 light years or 30,800,000,000,000 km.

kiloparsec (kpc) - 1000 parsecs.

Megaparsec (Mpc) - 1 million parsecs.

The Cosmic Distance Scale was created by Maggie Masetti. Scientific Oversight was provided by Dr. Koji Mukai.

This file was last modified on Tuesday, 11-Mar-2008 16:02:48 EDT