XMM-Newton: ESA’s multi-mirror X-ray detector
ESA's XMM-Newton X-ray observatory is the biggest space observatory ever built in Europe. Weighing 3.8 tonnes at launch, the spacecraft is 10 metres long and measures 16 metres across its two solar arrays. Its wafer-thin, gold-coated mirrors collect high-energy X-rays from all parts of the Universe, and its sensitive cameras can see much more than any previous X-ray satellite.
XMM-Newton was launched by a European Ariane 5 rocket on 10 December 1999. It was placed into an unusual 48-hour orbit around the Earth, with an altitude which varied between 7,000 km and 114,000 km. The mission was originally known as XMM after its X-ray Multi-Mirror design. The name was later changed to XMM-Newton, in honour of the famous British scientist Sir Isaac Newton.
Although its primary mission was to last for two years, XMM-Newton is still in good health. Operations have been extended until at least the end of 2014. This remarkable observatory has studied all kinds of objects, ranging from comets and planets in our Solar System to supermassive black holes and exploding stars in the further reaches of the Universe. During 14 years of operation, it has detected over half a million X-ray sources, twice as many as previously known.
These discoveries have been made possible by the observatory’s advanced design. Since X-rays pass straight through ordinary mirrors, each of XMM’s three barrel-shaped telescopes consists of 58 curved mirrors which are nested around each other. Incoming X-rays skim off the surfaces of these mirrors so that they are eventually focused onto two types of instrument fitted with CCD detectors (like those found in digital cameras). An optical camera allows astronomers to pinpoint their targets.