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BRIGHTER THAN A MILLION-BILLION SUNS


June 15, 1998: An ultra-luminous quasar--brighter than any object previously observed in the universe--has been discovered by University of Victoria astronomer, Dr. Geraint Lewis and three colleagues in Europe and the U.K.

The quasar is estimated to be at least four million-billion times brighter than the Sun. It's brighter than any other observed quasar by a factor of 10 and it outshines the brightest galaxy by more than 100 times.

"There is a lot of matter being thrown out of this quasar at very high velocities, tens of thousands of kilometres a second," Lewis said. "It has a lot which we feel astronomers will want to get their hands on. It will touch on several areas of extra-galactic astronomy."

Lewis and collaborators-Michael Irwin of the Royal Greenwich Observatory, Rodrigo Ibata of the European Southern Observatory in Munich and Edward Totten of Queen's University in Belfast-stumbled upon the discovery while investigating the collision between the Milky Way and the smaller Sagittarius Dwarf galaxy.

Looking for carbon stars, they noticed what appeared to be an unusually bright quasar. Suspicions were confirmed by images taken from the 2.5-meter Isaac Newton Telescope in the Canary Islands.

"It was actually a serendipitous discovery, as the best discoveries often are," said Lewis, who also conducts postdoctoral research at the University of Washington.

The team will make further observations with ground-based telescopes and the Hubble Space Telescope to confirm whether the quasar is as it appears or if the image is being distorted by gravity from another object, an effect known as gravitational lensing.

"The big question is, how can you feed in enough matter to generate enough energy to make this thing glow so brightly? The amount of energy that's released tells you something about how stars in galaxies like our own arose, their evolution and their history," Lewis said.

The quasar's brightness is generated by two sources. Light in the ultraviolet and optical range comes from an accretion disc surrounding a supermassive black hole. The second source is infrared light from thick dust heated by radiation from the quasar's centre.

The quasar is about 11 billion light years away, so the light now reaching Earth emanated when the universe was only 10 per cent of its present age.

News of the discovery is being carried in Thursday's edition of the British magazine Nature and the findings have been accepted for publication in the Astrophysical Journal, the world's leading research journal of astronomy and astrophysics.

Source: University of Victoria Press Release:
Mike McNeney (Communications) mmcneney@uvic.ca



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