A new study of very bright and ancient celestial objects called quasars finds that they are associated with fairly normal galaxies, surprising some astronomers.
Quasars are the brightest things in the distant universe. They are so bright that they overpower whatever galaxy might be associated with them. Each quasar is thought to be part of a developing galaxy that harbors a supermassive black hole at its core. Perhaps tremendous amounts of gas are falling toward the black hole, being superheated and generating the radiation, theorists suppose.
Astronomers had expected that a typical quasar's galaxy would be very massive or bright or perhaps physically distraught, having recently undergone a collision that sparked whatever activity is creating the intense luminosity.
But new observations of nine quasars with the Gemini Observatory in Hawaii show them to be humdrum, as the astronomers put it.
"It's like finding a Formula One racing car in a suburban garage," said study leader Scott Croom of the Anglo Australian Observatory in Australia.
Where's the galaxy?
In fact, in all but one of the nine cases the researchers made no firm detection of a galaxy at all, despite a sensitivity to infrared light they said equaled that of the Hubble Space Telescope. The Gemini Observatory used adaptive optics, which cancels blurring effects of the atmosphere, to gain the quality views.
"These observations should really have been like using a magnifying glass to find an elephant," said team member Tom Shanks of Britain's University of Durham. "Instead, the host galaxies turned out to be more like little mice, despite their brilliant roar."
The lone galaxy detected with certainty in the study was described as "remarkably unremarkable," similar in size and brightness to our Milky Way.
Rethinking the model
The Milky Way harbors a supermassive black hole, but the setup is comparatively inactive and so does not qualify the galaxy to be termed a quasar. Astronomers think the Milky Way may once have been a quasar, though.
"We may need to rethink our models of how quasars work," said David Schade of the National Research Council Canada, who presented the observations at a Gemini Science Conference in Vancouver on Tuesday. The results were also published in the Astrophysical Journal.
The researchers speculate that quasars were generated mostly in the early universe by black holes swallowing large quantities of cold, dense gas that was more common back then. Much of that gas has since been consumed by black holes or turned into stars.
Quasars, short for quasi-stellar radio sources, were first noticed in the 1950s and ’60s and were thought to be nearby stars that behaved strangely. But by measuring their redshift (the change in the wavelength of light emanating from the object based on whether it moves toward or away from us) astronomers learned quasars were billions of light-years away.