Quasars have remained enigmatic ever since their discovery in 1963 because of the way they emit prodigious amounts of energy yet are very compact. Their star-like appearance gave birth to the name quasi-stellar object, later shortened 'to 'quasar'. The most widely accepted theory to explain quasars is that they are powered by supermassive black holes in the cores of galaxies.
This HST image of the quasar PKS 2349 shows evidence that it is merging with a companion galaxy. The bright central object is the quasar itself, which is several billion light years away. The wisps next to it are remnants of a bright galaxy that has been disrupted by the gravitational pull between it and the quasar.
Credit: J. Bahcall (Institute for Advanced Study, Princeton), and NASA