Encyclopedia  |   World Factbook  |   World Flags  |   Reference Tables  |   List of Lists     
   Academic Disciplines  |   Historical Timeline  |   Themed Timelines  |   Biographies  |   How-Tos     
Sponsor by The Tattoo Collection
J2000.0
Main Page | See live article | Alphabetical index

J2000.0

The J2000.0 epoch is used in astronomy.

It is precisely Julian date 2451545.0 TT, or January 1 2000, 12h TT. This is equivalent to January 1 2000, 11:59:27.816 TAI or January 1 2000, 11:58:55.816 UTC.

Since the right ascension and declination of stars are constantly changing due to precession, astronomers always specify these with reference to a particular epoch. The earlier epoch that was in standard use was the B1950.0 epoch.

The "J" in the prefix indicates that it is a Julian epoch, as opposed to a Besselian epoch.

External links