Wikipedia
XMM-Newton, also known as the High Throughput X-ray Spectroscopy Mission and the X-ray Multi-Mirror Mission, is an X-ray space observatory launched by the European Space Agency in December 1999 on an Ariane 5 rocket. It is the second cornerstone mission of ESA's Horizon 2000 programme. Named for physicist and astronomer Sir Isaac Newton, the spacecraft is tasked with investigating interstellar X-ray sources, performing narrow- and broad-range spectroscopy, and performing the first simultaneous imaging of objects in both X-ray and optical ( visible and ultraviolet) wavelengths. Originally scheduled for a two-year mission, the spacecraft remains in good health and has received mission extensions through 2016. As of February 2016, more than 4,300 papers have been published about either XMM-Newton or the scientific results it has returned.