Discovered: New type of quasar

A new class of quasar has given a team of astronomers more than they bargained for.

A visible-light wide-field image of a distant quasar.

A visible-light wide-field image of a distant quasar.

A new breed of quasar found to be glowing brightly in some distant galaxies has been uncovered by an international team of astronomers. However what’s interesting about this particular type is that current theories do not predict their existence.

We know that supermassive black holes can be found at the centres of massive galaxies, like our Milky Way. Some of these exotic objects are surrounded by a disk of white hot gas that astronomers dub a quasar. These bright objects are capable of creating enough light to be seen across the observable Universe, measuring larger than Earth’s orbit and sizzling at temperatures hotter than the Sun. But there’s something extremely peculiar about this new class.

“Gas in the disk must eventually fall into the black hole to power the quasar, 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,” says lead scientist of the study, Patrick Hall of York University in Canada. However, the team has found that this is not what’s happening here.

“The gas in this new type of quasar is moving in two directions: some is moving toward Earth but most of it is moving at high velocities away from us, possibly toward the quasar’s black hole,” Niel Brandt, a Professor of Astronomy and Astrophysics at Penn State University tells All About Space. “Just as you can use the Doppler Shift for sound to tell if an airplane is moving away from you or toward you, we used the Doppler shift for light to tell whether the gas in these quasars is moving away from Earth or toward these distant black holes.”

The team came across the mysterious quasars with data from the Sloan Digital Sky Survey, a major multi-filter imaging and spectroscopic redshift survey that uses a 2.5-metre wide-angle optical telescope at Apache Point Observatory in New Mexico. They realised that the gas in these distant objects was unusual to say the least with only around 1 of 10,000 possessing it. And, with only seventeen cases known, the team is currently faced with a puzzle that our current understanding of these objects struggles to solve – at least without being mapped out further.

An illustration of one of two possibilities. Here the gas of the quasar is flowing into the black hole.

An illustration of one of two possibilities. Here the gas of the quasar is flowing into the black hole.

“The two main possibilities are high velocity infalling gas or rotating outflows where the rotational motion dominates over the outflow motion,” muses Brandt. “The observation can likely be accommodated within our current theories, however, they do require interesting extensions of these theories and there are some remaining challenges in explaining the detailed aspects of the redshifted absorption lines.”

Brandt elaborates on these so-called absorption lines. “These quasars have gas closely associated with the quasar that imprints redshifted broad absorption lines,” he says. “This is a novel phenomenon.”

The new finding might have challenged what we know about our Universe and the objects in it, but not prepared to give up that easily, the team intend to carry out further studies. One of their main aims is to study the time variability of the redshifted absorption lines that will hopefully provide assistance in locking down a model for the quasars.

“We’d also like to obtain X-ray measurements to determine the level of X-ray absorbing gas along the line of sight and near-infrared spectroscopy can give us access to additional emission lines to characterise the quasar properties,” Brandt adds.

Images courtesy of ESO/Digitized Sky Survey/Davide De Martin (top) and York University (bottom)

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