The Athena X-ray observatory is the second large mission (L2) of ESA's Cosmic Vision-programme. Athena has a planned launch date in 2028. The space telescope will answer two big scientific questions: How and why does ordinary matter glue together into the Milky Way and clusters of galaxies we see nowadays? And how do black holes grow and influence their surroundings?
Athena will observe the hot universe for at least 5 years. The telescope will carry two instruments: the camera annex spectrometer X-IFU (X-ray Integral Field Unit) and the Wide Field Imager (WFI). SRON is co-Principal Investigator (co-PI) for X-IFU and carries out the parallel development of back-up ultra-sensitive detector arrays for X-IFU. Athena is ESA's second large mission in the Cosmic Vision programme, after Juice, the mission which will study Jupiter and its moons. Juice has a planned launch date in 2022.
The X-ray telescope Athena will study spectacular phenomena nearby black holes and neutron stars. Moreover Athena will for the first time determine very accurately the composition of the hot matter (more than 10 million degrees) in clusters of galaxies.
Accretion onto black holes is one of the major astrophysical energy generation processes, and its influence via cosmic feedback is profound and widespread. X-ray observations provide unique information about the physics of black hole growth and the causes and effects of the subsequent energy output, as well as revealing where in the Universe black hole accretion is occurring and how it evolves to the highest redshifts.
The bulk of visible matter in the Universe comprises hot gas which can only be accessed via space-based facilities operating in the X-ray band. Revealing this gas and relating its physical properties and evolution to the cosmological large-scale structure, and the cool components in galaxies and stars, is essential if we are to have a complete picture of our Universe.
SRON is one of the leading institutes in the development of the X-ray Integral Field Unit (X-IFU) for Athena. X-IFU will be a 2-D imaging camera annex spectrograph that is cooled to sub-Kelvin level. The spectrograph will be able to produce a spectrum for each pixel of the captured image and derive the characteristics of gas as hot as 10 million degrees Kelvin.
Crucial to this set-up are TES-detectors (by NASA Goddard Space Flight Center) and their read-out (SRON). Apart from the readout, SRON develops the back-up TES detector arrays. TES detector arrays are super sensitive in showing very slight temperature changes when photons are absorbed in the connected absorber. The change in temperature is a measure of the energy of the detected X-ray photon. The accurate energies of the X-ray light detected by Athena will give astronomers highly valued information about the quantity and type of gases that black holes blast into space, for example. SRON develops the read-out for either detector-type.
Athena's big lens will lead the captured X-rays to the detector, which will consist of 4000 independent sensors (pixels). These sensors will be mounted on a membrane of silicon nitride to prevent, if possible, any increase in temperature. That is why the deeply cooled camera can make very detailed pictures of the universe, with a detailed spectrum for every sensor.
Athena history in bullets:
- end-1990s, discussions start on the follow-up of ESA's XMM-Newton (launched in 1999)
- the proposed follow-up, XEUS, is not selected for the ESA Cosmic Vision L1 call
- EU and US consortia merge into IXO instead of XEUS
- ESA requires a EU-led mission in 2011 and IXO becomes Athena
- Athena is still down-selected
- Athena becomes Athena+ in 2013
- the Athena+ science theme, "the hot and energetic Universe”, is selected by ESA in Nov 2013
- Athena is selected by ESA in June 2014.