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More than 350 keywords from relativity and related topics, from "absolute zero" to "X-rays" - please use the menu on the left to choose a letter.

 X-ray astronomy

Branch of physics devoted to the observation of X-rays reaching us from the depths of space. Such radiation is typically produced as the thermal radiation of matter at extremely high temperatures - an important example are the hot gases in the accretion disc of a black hole.


Highly energetic electromagnetic waves with frequencies between a few hundred Quadrillions and a few hundred Quintillions of oscillations per second, corresponding to wave-lengths of a few billionths to a few trillionths of a metre. Most people know of these ray's medical applications - with their help, one can produce images of the interior of human bodies - however, they are also used in (X-ray) astronomy.

 XMM Newton

Satellite project of the European space agency ESA. Launched in December 1999, XMM Newton is a space-based X-ray telescope; as such it is especially suited for research on the luminous phenomena associated with black holes.

XMM-Newton Science Operations Centre Home Page (ESA)