15 Years of Exploration

They named it after American astronomer Edwin Hubble, who confirmed the theory of an expanding universe, and the Hubble Space Telescope -- "the Hubble" as it is known to countless admirers -- has done him proud.

Today, the Hubble marks its 15th anniversary in orbit, a remarkable period in which it has helped fix the age of the universe (at 13.7 billion years), confirmed the presence of black holes in the middle of galaxies, discovered dust disks that lead to the formation of planets around young stars, taken snapshots of the universe shortly after it was formed in the Big Bang, determined the atmospheric composition of a planet orbiting another star and made crucial contributions to the study of the "dark energy" responsible for accelerating the expansion of the universe.

Its scientific findings and images like these -- of stars, planets, nebulae, galaxies, quasars, brown dwarfs, supernovae and other cosmic exotica -- have astounded astronomers and amateur star-lovers alike. More than 4,000 scientific papers have been produced from Hubble research, making it one of the most important scientific instruments ever built.

Launched from the space shuttle Discovery on Apr. 24, 1990, Hubble orbits the Earth at an altitude of 353 miles. It weighs 24,500 pounds and stands 43.5 feet tall -- about the size of a large schoolbus.

Maintained and upgraded periodically with new instruments since launch, NASA in 2004 canceled Hubble's fifth shuttle servicing mission. This decision is now being reviewed, but if it is not reversed, the telescope's gyros or batteries will give out sometime after 2007, and Hubble will shut down.