X-ray astronomy

The optical test set-up for a prototype nickel mirror on the Chandra X-Ray Observatory.

The Chandra X-Ray Observatory prior to deployment during shuttle mission STS-93. Space shuttle Columbia is poised above the virtually cloudless coastal desert of Namibia, West Africa.

The solar arrays of the Chandra X-Ray Observatory. The sunshade door is one of the most vital elements of the spacecraft system. It remained closed until the Chandra X-Ray Observatory achieved its correct orbital attitude. Once opened, it shadows the entrance of the telescope to allow it to point as close as 45° to the Sun.

Detection of X-rays from intensely hot gas in the universe. Such X-rays are prevented from reaching the Earth's surface by the atmosphere, so detectors must be placed in rockets and satellites. The first celestial X-ray source, Scorpius X-1, was discovered by a rocket flight in 1962.

Since 1970, special satellites have been put into orbit to study X-rays from the Sun, stars, and galaxies. These include the Chandra X-Ray Observatory and the Röntgen Satellite. Many X-ray sources are believed to be gas falling into neutron stars and black holes.