"20th Anniversary of Hubble Telescope Launch" - this was the first news I got to know from Google's main page today.
Hubble Telescope was launched on 24th of April, 1990 using Space Shuttle. 2o years have come, but Hubble is still one of the largest and most powerful telescope. It has a great value for astronomers all over the world as it provides images of distant space whose resolution is many times greater than resolution of any other telescope.
But the beginning of Hubble's mission was not so succesful: just after launch scientists found that main mirror had been ground incorrectly. This defect was restored during the servicing mission in 1993. Hubble is the only telescope that can be serviced in space by austronauts. So, it has been already serviced five times. The last mission was carried out in 2009. Hubble mission will stay in space until at least 2014, after what its successor infrared James Webb Space Telescope will be launched.
The Telescope was named after Edwin Powell Hubble (1889 - 1953), American astronomer who is credited with some significant discoveries. He was the first who demonstrated existence of galaxies, other than our own, Milky Way. Another Hubble's discovery was proof that the Universe is being expended. Hubble noticed that degree of Dopler effect (is when all the light from object shifts to the red part of spectrum) depends on distance to the galaxy, i.e. greater the distance, greater the degree of Dopler effect. This fact is very important as it supports Big Bang model of the Universe. According to this model, the Universe come into existance from extremely dence and hot state 13.9 billion years ago.
Here are some greatest photos of the Universe made by Hubble Telescope.
You can learn much more about Hubble Telescope on Wikipedia.
Excelent collection of pictures made by Hubble Telescope is taken from the site of European Space Agency.