AUSTIN, Texas — Researchers at The University of Texas at Austin have found
new evidence to suggest that all radio-loud quasars may be blazars — and the
differences between them may be related to the angle from which they are
viewed. Quasars are quasi-stellar objects found in distant reaches of the
universe and blazars are much brighter types of quasars.

After a spectroscopic survey of 62 quasars using the H.J. Smith telescope at
UT Austin’s McDonald Observatory, astronomers Dr. Feng Ma and Dr. Beverley
Wills say there is new ultraviolet evidence suggesting that radio-loud
quasars are simply blazars seen from the side. Their work will be published
Friday (June 15) in the journal Science.

“A blazar is a special type of quasar that beams an intense jet of radiation
in our direction. It’s as if we’re looking into a searchlight beam,” said
Wills, a McDonald Observatory research scientist.

A quasar is a star-like object that emits more energy than 100 giant galaxies
combined and is among the most distant objects found so far in the universe.
The brilliance of a quasar is believed to originate from swirling gas and
stars in the process of falling into a gigantic black hole at the quasar’s

About 10 percent of all quasars catalogued by astronomers are referred to
as radio-loud quasars because they are more luminous (or louder) at radio
wavelengths than optical wavelengths. The strong radio emission of a radio-
loud quasar results from two jets of energetic particles shooting away from
the center of the quasar in opposite directions.

Wills explained that some of the radio-loud quasars are much more luminous
than other quasars “and randomly change their brightness, even from hour to
hour. These are classified as blazars.”

Ma, a graduate research assistant in the Microelectronics Research Center
in the UT Austin College of Engineering, said the blazar’s powerful
radiation also could be compared to a flashlight beam. “For most quasars,
we are looking from the side, not directly into the beam, so we don’t really
see the jets. But some have their beams pointing at us, and we call them
blazars,” Ma said.

Wills said the scientists found evidence from spectra of several quasars
suggesting that the unseen jets “heat up the gas swirling around the center
and we see this glowing gas. This is like seeing light from a searchlight
beam as the beam pierces a cloud, even though the searchlight may not be
pointing in our direction. This is new, direct evidence from ultraviolet
light that every radio-loud quasar has jets.”

Ma said this phenomenon was predicted in the Astrophysical Journal Letters
in a paper titled “Does Every Quasar Harbor a Blazar?” that he and Wills
published in 1998 before observations were completed.

“Our work will also have an influence on a method astronomers use to study
cosmology,” Ma added. “Because blazars are highly variable, radio-loud
quasars should all be excluded when using (the brightness of) quasars to
measure distances in the universe.”

For more information, contact Dr. Feng Ma at (512) 471-3644 or (512) 232-4690
or Dr. Beverley Wills at (512) 471-3424. For a Powerpoint presentation, see: