X-ray Astronomy

stars emit a variety of electromagnetic radiation including X-rays, but this is unable to penetrate the Earth's atmosphere to be detected. Very hot stars send out large amounts of X-rays which can be detected by equipment contained on space satellites. The satellite ROSAT launched in 1990 has equipment to undertake X-ray astronomy and obtain information about distant bodies in space (e.g. WHITE DWARFS and SUPERNOVAE) that are emitting X-rays.

Taken from Dictionary of Science

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X-ray astronomy is an observational branch of astronomy which deals with the study of X-ray emission from celestial objects. X-radiation is absorbed by the Earth's atmosphere, so instruments to detect X-rays must be taken to high altitude by balloons, sounding rockets, and satellites. X-ray astronomy is part of space science.

X-ray emission is expected in sources which contain an extremely hot gas at temperatures from a million to hundred million degrees kelvin. In general, this occurs in objects where the atoms and/or electrons have a very high energy. The discovery of the first cosmic X-ray source in 1962 came as a surprise. This source is called Scorpius X-1, the first X-ray source found in the constellation Scorpius. Based on discoveries in this new field, Riccardo Giacconi received the Nobel Prize in Physics in 2002. It was found that the X-ray emission of Sco X-1 was 10,000 times greater than its optical emission, based on a precise location obtained with a modulation collimator - a specific type of coded aperture imager. In addition, the energy output in X-rays is 100,000 times greater than the total emission of the Sun in all wavelengths. It is now known that such X-ray sources are compact stars, such as neutron stars and black holes. The energy source is gravity. Gas is heated by the fall in the strong gravitational field of celestial objects.

Many thousands of X-ray sources are known. In addition, it appears that the space between galaxies in a cluster of galaxies is filled with a very hot, but very dilute gas at a temperature between 10 and 100 megakelvin (MK). The total amount of hot gas is five to ten times the total mass in the visible galaxies.

Taken from Wikipedia