Future X‐ray Missions to Study Relativistic Astrophysics Available to Purchase

In order to revolutionize the current understanding of the high energy universe, a number of new X‐ray missions are being developed and planned. Among them, e‐ROSITA/SRG, NuSTAR, ASTROSAT, GEMS and ASTRO‐H will be realized in the next decade. And then, much larger missions, such as IXO, have been proposed for the 2020’s. NuSTAR and ASTRO‐H will open up completely new field of spatial studies of non‐thermal emission above 10 keV by hard X‐ray telescopes. They will also uniquely allow mapping of the spatial extent of the hard X‐ray emission in diffuse sources, thus tracing the sites of particle acceleration in structures ranging in size from clusters of galaxies down to supernova remnants. Multi‐wavelength spectra by ASTROSAT and ASTRO‐H are indispensable to understand physical processes in high energy phenomena, such as particle acceleration in the Universe. Imaging spectroscopy with an energy resolution $<5–7 eV$ brought by the micro‐calorimeter onboard ASTRO‐H can reveal line broadening and Doppler shifts due to turbulent or bulk velocities in extended sources. GEMS will perform the first sensitive X‐ray polarization survey of several classes of X‐ray emitting sources characterized by strong gravitational or magnetic fields. Here we present the key science goals for future X‐ray missions designed to address a number of fundamental questions in contemporary astrophysics.