Quasar. Coloured Chandra X-ray telescope image of the quasar PKS 0637-752. A bright jet extends to the right of the quasar, which is though to be made up of ejected high energy particles. Quasars are the most distant objects known, but are visible as they are extremely luminous. PKS 0637- 752 has the power of 10 trillion Suns. Quasars are thought to be active galactic nuclei, galaxies with a supermassive black hole at their heart. The X-ray emission derives from matter being heated in an accretion disc as it nears the hole. PKS 0637- 752 lies around six billion light years from Earth in the constellation Mensa. Image made by the Advanced CCD Imaging Spectrometer (ACIS) in 1999.