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Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

See Explanation. Clicking on the picture will download the highest resolution version available.

The Decade that Defined Star System

Explanation: As the 1990s began, the only planetary star system known was our own Solar System . The first extra-solar star system was discovered orbiting a pulsar in 1991. Slight changes in the precise arrival times of the pulses from the central small dense neutron star gave evidence of orbiting planets . By mid-decade Jupiter -like planets around Sun -like stars were being found by a slight wobble detected in the motion of these stars. Pictured above is an artist's sketch of a planet discovered orbiting HD217107 . As the decade comes to a close, over two dozen planetary star systems have been identified, one recently confirmed by the detection of a slight eclipse by the planet itself. An unambiguous discovery of Sun-like star systems containing Earth -like planets still remains a goal.

Date December 29, 1999
Credit Drawing Credit & Copyright: Lynette Cook
Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
A service of: ASD at NASA / GSFC,
NASA Science Activation & Michigan Tech. U.