The entire sky in hard X-rays as viewed by INTEGRAL
This image shows the sky at hard X-ray energies as seen by ESA's INTEGRAL observatory. The data have been collected with the IBIS/ISGRI instrument on board INTEGRAL in the 18–40 keV energy range (as a comparison, visible light corresponds to 1.65–3.1 eV).
Most of the sources shown in the image belong to our Galaxy, the Milky Way, and are concentrated along the Galactic Plane and Bulge. These objects mainly correspond to the late stages of stellar evolution and are characterised by strong emission in the high-energy end of the electromagnetic spectrum, at X- and gamma-rays.
The majority of sources depicted in the image are X-ray binaries: binary systems containing a compact stellar remnant (a black hole or a neutron star) that exerts an intense gravitational pull on its companion star and thus accretes material from it. Other types of galactic sources shown are rotating neutron stars, also known as pulsars, and supernova remnants.
A few extragalactic sources – active galactic nuclei – can also be seen, mainly at higher galactic latitudes.
The sources are represented in false colours. The colour code used here reflects the characteristics of their emission across the hard X-ray portion of the spectrum: sources shown in red have a "softer" spectrum, meaning that they emit more at lower energies than at higher energies, whereas sources represented in blue have a "harder" spectrum, characterised by strong emission at both higher and lower energies; sources indicated in white/yellow/green have intermediate characteristics between these two extremes.