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On this day in 1999 – December 10th – the European Space Agency (ESA) launched the Newton X-Ray Multi-Mirror Telescope (XMM-Newton).

XMM-Newton, named after Sir Isaac Newton, investigates interstellar X-ray sources and performed the first simultaneous imaging of objects in both X-ray and optical (visible and ultraviolet) wavelengths. Although planned to be operational for 10 years, the telescope is still in operation.