Scientists Discover New Category of Quasar


Mimi Liu
Staff Writer

The brightest things in the universe are also the most mysterious. Scientists have just discovered a new kind of quasar, a bright galactic core powered by a supermassive black hole, that is unexplained by current theories.

“Quasar” is short for a quasi-stellar radio source, a term first coined by astronomers in the early 1960s. When astronomers measured radio waves emanating from what they expected to be galaxies, they instead saw blue star-like objects, hence, “quasi-stellar.” When the light from these objects was analyzed, redshift was observed, meaning that quasars are moving rapidly away from Earth.

Quasars produce “enough light to be seen across the observable universe,” York University officials said in a statement.

They generate more energy than over a hundred galaxies combined, and can be a trillion times brighter than our sun. The reason is that matter is actually converted to energy in the supermassive black holes at the centers. Quasars are so bright that they outshine all other stars in the galaxy in wich they are located, resulting in their quasi-star-like appearance.

Current theory predicts that quasars will push gas outward, from their nucleus to the edges. The newly discovered quasars do the same—but interestingly enough, some of that gas is falling inwards.

“Matter falling into black holes may not sound surprising,” said lead scientist Patrick Hall, an astronomer at York University in Toronto, Canada. “But what we found is, in fact, quite mysterious and was not predicted by current theories.”

The gas flow of quasars can be observed by using the Doppler effect and observing the wavelength shifts. The Doppler effect is the stretching and shrinking of wavelengths as an object moves toward and away from a stationary object. This come into practice, for example, in the way the sound of a police car’s siren seems to alter as it drives past you.

“The gas in the disk must eventually fall into the black hole to power the quasar,” Hall said, “but what is often seen instead is gas blown away from the black hole by the heat and light of the quasar, heading toward us at velocities up to 20 percent of the speed of light.”

“If the gas is falling into the black hole, then we don’t understand why it’s so rare to see infalling gas,” he added. “There’s nothing else unusual about these quasars. If gas can be seen falling into them, why not in other quasars?”

One explanation is that the gas expelled from these quasars do not immediately leave, but rather circle in a way that part of it spirals back to the center.

“To make an analogy: Imagine an ant on a spinning merry-go-round, crawling from the center to the edge,” Hall said. “You will see the ant moving toward you about half the time and away from you about half the time. The same idea could apply to the gas in these quasars. In either case, the gas in these quasars is moving in an unusual fashion.”

The quasars were discovered using the Sloan Digital Sky Survey (SDSS-III), and scientists plan follow-up surveys using the Gemini Observatory. Seventeen of these new objects have been discovered, and scientists predict that they make up 0.01 percent of all quasars.