Athena (Advanced Telescope for High ENergy Astrophysics) is a general-purpose open X-ray observatory that was selected by ESA in June 2014 as the second Large mission opportunity within its Cosmic Vision programme. The mission was selected to address the Hot and Energetic Universe scientific theme. However, the observatory will have a profound impact in many areas of astrophysics. 

As stated at the ESA Cosmos web portal, the mission will be “a powerful X-ray observatory with an unprecedented combination of collecting area, survey capabilities and energy resolution”. Its unprecedented capabilities will allow the astronomical community to address a wide range of astrophysics topics, yet to be defined by the community in open calls. These topics might include among others: accreting compact objects such as black holes over their whole mass range and neutron stars, the hot gas around clusters of galaxies, distant gamma-ray bursts, supernova explosions and remnants, stars, white dwarfs, exoplanets and their parent stars, and the interstellar medium. See the Science menu for more details.

The observatory will consist of a single large-aperture grazing-incidence X-ray telescope, utilising a novel technology (high-performance Si pore optics) developed in Europe, with a 12m focal length and 9 arcsec HEW on-axis angular resolution. The focal plane contains two instruments. One is the Wide Field Imager (WFI) providing sensitive wide-field imaging and spectroscopy and high count-rate capability. The other one is the X-ray Integral Field Unit (X-IFU) delivering spatially resolved high-resolution X-ray spectroscopy over a  field of view a few arcminutes across. See the Mission menu for more details.

With its unparalleled capabilities, the telescope will be a truly transformational open observatory, operating in conjunction and synergy with other large observatories across the multi-messenger landscape in the second half of the 2030s.