Well-known for its spectacular photographs of the universe, the Hubble Space Telescope has recorded its one millionth observation -- and ironically, it wasn't a photograph at all. Instead, it was a detailed analysis of the chemical makeup of an exoplanet's atmosphere, from which NASA released an artist's conception (see slide #11 below).
In its 21-year history, Hubble has recorded 50 terabytes of images and other scientific data, according to NASA. Despite Hubble's usefulness to scientists around the world, its lifespan is coming to a close. Its last servicing mission from a space shuttle was designed to keep the telescope going only until about 2013.
But researchers won't be without orbiting telescopes, which are often necessary to obtain the clearest observations in light that is filtered out by Earth's atmosphere. In addition to other telescopes currently in orbit, NASA plans on launching Hubble's successor, of sorts, the James Webb Space Telescope, in 2015. In preparation for that launch, NASA has requested about $373 million for FY2012, and plans on similar amounts in following years.
Selecting the best few photos from Hubble's history is not easy; below is a sampling of some of the telescope's most recent images.