“Go ahead” for Athena!
ESA’s Science Program Committee (SPC) has selected the Athena project for its next large (€1bn-class) mission, due for launch in 2028.
The Advanced Telescope for High-Energy Astrophysics has been specifically designed to address the “Hot and Energetic Universe” theme, chosen by ESA as its most urgent scientific priority to be tackled by a large space mission. The theme poses two key astrophysical questions: 1) How does ordinary matter assemble into the large-scale structures we see today? and 2) How do black holes grow and shape the Universe?
Athena answers these by combining both spatially-resolved X-ray spectroscopy and deep wide-field X-ray spectral imaging with a performance greatly exceeding that offered by existing X-ray observatories. In designing a mission to address these questions, an international team of astronomers, including scientists at the Max Planck Institute for Extraterrestrial Physics, Bonn University and other German institutes, first had to formulate specific observational tests. Supermassive black holes need to be revealed even in obscured environments, out into the early Universe, and both the inflows and outflows of matter and energy need to be tracked as the black holes grow. In terms of the growth of cosmic structures, the scientists need to map hot gas in the Universe - specifically the gas in clusters and groups of galaxies, and the intergalactic medium – determining their physical properties, tracking their evolution through cosmic time.
“Athena will revolutionise our view of black holes and cosmic structures filled with million degree gas. We really need this to build a holistic picture of the observable Universe” said MPE Director Paul Nandra, spokesperson for the Hot and Energetic Universe science theme and lead investigator of the Athena proposal.
The Athena mission
A detailed analysis of the scientific questions underlying the Hot and Energetic Universe theme enabled the team to set the key performance parameters for the mission. Athena will need an X-ray telescope that combines an unprecedentedly large collecting area (2 m2 at 1 keV) with excellent angular resolution (5”) and a wide field of view. The telescope focuses X-ray photons onto one of two instruments, which can be moved in and out of the focal plane using a movable instrument platform. The first instrument, the X-ray Integral Field Unit provides spatially-resolved high resolution spectroscopy. The second instrument, the Wide Field Imager is a Silicon-based detector using DEPFET Active Pixel Sensor technology developed at the Max Planck Institute for Extraterrestrial Physics. The camera will provide a large sky coverage coupled with a high time resolution of around 10μs as well as high count rate capability. "This synthesis makes the WFI an extremely powerful instrument, allowing us to conduct deep surveys for faint sources one hundred times more efficient than currently possible. At the same time we will be able to study the brightest X-ray sources in the sky," says WFI project scientist Arne Rau.
Athena will be operated as an observatory that users will be able to access via open proposal calls, so can be used to address a wide range of science questions across the whole of astrophysics. The selection of Athena for a launch in 2028 will guarantee a transformation in our understanding of The Hot and Energetic Universe. It will also provide an essential complement to contemporary facilities working in other wavebands in that timeframe.
“It’s been an amazing journey getting the project this far” added Nandra. “Hundreds of scientists have dedicated their efforts and inspirational ideas about the Universe to make the case for Athena. Today their dreams of transforming our view of the observable Universe will start to come true. Now all we have to do is build it.”