Credit: ESA/XMM-Newton/ R. Saxton / A.M. Read, CC BY-SA 3.0 IGO
The XMM-Newton X-ray telescope was launched in 1999 and is orbiting earth since then. Its mission is to study high-energy phenomena in the Universe, such as black holes and neutron stars. When the telescope moves between specific target it stills collects scientific data (slews).
The map shows 30,000 sources detected during 2114 of these slews. Some of the sources have been observed up to 15 times. After correcting for overlaps between slews, 84% of the sky has been covered. Lower energy sources are shown in red while higher energy sources are blue. The size of each source is proportional to its brightness.
The centre of the plot corresponds to the centre of the Milky Way. Objects above and below the centre of the plane of our Galaxy are mostly external galaxies that are emitting X-rays from their massive balck holes.