In this map of a celestial hemisphere — compiled from data from the #eROSITA telescope — the colours reflect the wavelengths of X-rays. Hot gas haloes surrounding galaxy clusters have broad-band emissions (white), as do black holes (white dots); diffuse emissions have long wavelengths (red); and in the central regions of the Milky Way, dust blocks longer-wavelength emissions, so that only short-wavelength X-rays are visible (blue or black).