The X-ray Multi-Mirror (XMM-Newton) mission is a joint project of the European Space Agency (ESA) and NASA. XMM-Newton is designed to observe high-energy X-rays emitted by exotic astronomical objects such as pulsars, black holes, and active galaxies. The observatory collects both images and spectra. This means it can measure the energy of the X-rays emitted by an astronomical object, which allows scientists to determine many of its physical characteristics. Besides having funded elements of the XMM-Newton instrument package, NASA also provides the NASA Guest Observer Facility (GOF) for XMM Newton at Goddard Space Flight Center. ESA launched the mission in December 1999.