Athena is Alive! NewAthena, the future of X-ray astrophysics

Prof A M Cruise
Emeritus Professor, University of Birmingham
 

The past two years have been a period of intense concern among Athena supporters and intense hard work by the Science Re-Definition Team. After the decision by the ESA SPC to reinstate the mission in the long-term science programme it is now time to stand back and visualise what a successful Athena mission can do for astronomy.

Clearly, the availability in the next few decades of an observatory with high sensitivity and good spatial resolution will support many areas of multi-messenger astronomy as well as continuing studies of galaxy clusters, galaxy evolution, compact objects and stellar physics for a long time to come. Even emerging fields such as exoplanet studies will benefit from a high-quality X-ray observatory for comparative studies.

But if Athena is to make its mark on astronomical history it must take advantage of its unique capability to make high-resolution spectral maps of extended sources of X-rays. The spectral resolution expected from Athena will bring the ability to measure the composition of the emitting gas, its temperature and in many cases the motion of the gas as well. Such diagnostic capabilities have not been available before combined with the sensitivity and spatial resolution that Athena can provide, heralding a new phase in X-ray astrophysics, a phase in which we can model and understand the properties and influence of hot gas in some of the largest structures in the Cosmos.

The power of exceptionally high spectral resolution for mapping gas dynamics inside clusters of galaxies should allow measurement of the temperature, composition and velocity of the component parts of clusters, radically improving our understanding of these fundamental building blocks of the Universe.  How do clusters form from the Cosmic Web left by the Big Bang? What role do massive black holes play in their evolution? Can we detect remnants of the Cosmic Web on the outskirts of clusters? These are all questions which need an understanding of the gas composition, gas flow and temperature at different positions throughout a cluster of galaxies- all questions that will need data from Athena to answer them. Taking spectral images with Athena will be just the first step in the journey to understand these huge objects. Complex atomic and plasma physics will be needed to interpret the data and sophisticated modelling of the gas flow and temperature will be able to test theories against the images that Athena will deliver.

Now that a major uncertainty over the future of Athena has been lifted, astronomers can plan for a deeper view of the Universe than available from any other mission.