Quasars or quasi-stellar radio source are sources of electromagnetic
energy which are characterized with high red shifts, thus leading scientists to conclude that not only they are moving away
but are also at a great distance from us. Of the over 100,000 quasars identified to-date, the greatest proportion are over
one billion light-years away (the closest quasar identified to-date is 780 million light-years away whereas the most distant
quasar discovered so far is 13 billion light-years away). As a result, quasars represent entities from the universe's
distant past.
Given their visibility (generally as point sources of light), it follows they must be associated with tremendous amounts
of energy which is only exceeded in intensity by supernovae and gamma-ray bursts. Some examples of quasars also involve
the centers of (active) galaxies and which has led to the suggestion that supermassive black holes at the galaxy center
and the consequent accretion of material must fuel these quasars. The rapid change in luminosity observed for some quasars
also suggests they must be relatively small entities.
Note: Quasar APM 08279+5255 lies at a distance of approximately 12 billion light-years away and
yet shines at magnitude 15.2! This combination of great distance and brightness makes it the
brightest object in the night sky (equivalent to
100 billion suns) and, furthermore, is a rare
example of gravitational lensing with three components (usually the number of components is even-numbered such as 2 or 4).
High resolution images by the Hubble Space Telescope have revealed the three components due to lensing by an intermediate
galaxy not visible in our light of sight to be separated by no more than 0.4". With an updated redshift of
3.91 (!), this extremely luminous and highly
red-shifted quasar is believed to possess a huge supermassive black hole at its center. Its age (12 billion years old) suggests
that it was created a mere 1.5 billion years after the creation of the universe.
Note: An exciting study released July 22, 2011 by NASA scientists suggests that the largest reservoir
of water discovered in the Universe so far and involving the "equivalent to 140 trillion times all the water in the world's ocean"
has been discovered around APM 08279+5255 (click
here for further details).
Please click on the image below to display in higher resolution (1200 x 900)