Tuesday, December 9, 2008

A supernova is a stellar explosion; one of the most energetic explosive events in the universe. This supernova explosion occur at the end of a star lifetime when its nuclear fuel is exhausted and it is no longer supported by the release of nuclear energy. They are extremely luminous and cause a burst of radiation that often briefly outshines an entire galaxy before fading from view over several weeks or months. During this short interval, a supernova can radiate as much energy as the Sun could emit over its life span. The explosion expels much of a star's material at a velocity of up to a tenth the speed of light, driving a shock wave into the surrounding interstellar medium. This shock wave sweeps up an expanding shell of gas and dust called a supernova remnant.

With the development of the telescope, the field of supernova discovery has enlarged to other galaxies, starting with the 1885 observation of supernova S Andromedae in the Andromeda galaxy. The last supernova event to be seen in our galaxy was Kepler's star in 1604. This remnant has been studied by many X-ray astronomy satellites, including ROSAT. There are, however, many remnants of Supernovae explosions in our galaxy, that are seen as X-ray shell-like structures caused by the shock wave propagating out into the interstellar medium. Supernovae provide important information on cosmological distances. During the twentieth century, successful models for each type of supernova were developed, and scientists' comprehension of the role of supernovae in the star formation process is growing. Some of the most distant supernovae recently observed appeared dimmer than expected. This has provided evidence that the expansion of the universe may be accelerating.