This animation seems to be available at only one other place on YouTube. It's of interest from any point of view. Credit: NASA /ESA. However, some of the smaller point-source objects didn't have a match. Astronomers called them "quasi-stellar radio. quasar: an astronomical object of very high luminosity found in the centres Photo AURA/STScI/ NASA /JPL (NASA photo # STScI-PRCa). Quasars quasar nasa also been discovered quasar nasa other techniques, including searches for starlike sources whose brightness varies irregularly and X-ray surveys from space; indeed, a high level of X-ray emission is regarded by astronomers as a sure indicator of an accreting black-hole. Although the first quasars known were discovered as radio sources, it was quickly realized that quasars could termine bremen september found more efficiently by looking for objects bluer than normal stars. It took years of study to realize that these distant specks, which seemed to indicate stars, are created by particles accelerated at velocities approaching the speed of light. Shining so brightly that they eclipse the ancient galaxies that contain them, quasars are distant objects powered by black holes a billion times as massive as our sun. There is a maximum rate set by the Eddington limit at which a black hole can accrete matter before the heating of the infalling gas results in so much outward pressure from radiation that the accretion stops. An even bigger surprise was that continuing observations of quasars revealed that their brightness can vary significantly on timescales as short as a few days, annoncen org that the total size of the quasar cannot be more than a few light-days .