The Hubble space telescope has been in orbit for 15 years, during which time it has taken over 750,000 images of the universe.

To celebrate, NASA has released two new pictures: one of a new area of the Eagle Nebula, a star forming region where hot dense gas is being shaped by ultraviolet light from a group of massive hot stars; the other of the Whirlpool Galaxy, with a smaller, companion galaxy on one of its arms.

The telescope didn't get off to the happiest of starts - when its first images were sent back to earth, NASA discovered that one of its mirrors was misshapen, so it was effectively myopic. However, since NASA scientists devised a fix for the problem, the telescope has made a huge scientific contribution. It has traced gamma ray bursts to their origins in distant galaxies, recorded the impact of a comet on Jupiter, proved the existence of super-massive black holes and pinned down the age of the universe.

Now, Hubble's future is under threat. Scheduled maintenance missions to Hubble were cancelled because of safety concerns raised by the Columbia Shuttle disaster, in which all astronauts on board were lost. This means Hubble will gradually break down. Engineers say it has enough power to keep going until 2008, but unless some kind of servicing mission can be mounted there will be no extra-atmospheric telescope until the 2011 launch of the James Webb Space Telescope. ®

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