Nov 15, 2018 | Updated: 03:14 AM EDT

Researchers Discover Dimming Switch on a Quasar

Jan 26, 2015 10:39 PM EST

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Scientists have long believed that at the center of quasars are massively powerful black holes.  However, a new study from Yale University researchers indicates the exact opposite may be true.  Researchers at Yale found that one particular quasar is actually dimming, and astronomers think it could be because of a black hole on a diet.

Quasars are usually the brightest, most energy-intense objects that we have discovered in the universe.  But over the last few years, scientists have observed one quasar has actually dimmed.  Scientists have previously observed quasars being swallowed by another black hole, but this is the first time they have noticed a dimming in one from only a single source.

"We've looked at hundreds of thousands of quasars at this point, and now we've found one that has switched off. This may tell us something about their lifetimes," lead author of the study from the Yale Center for Astronomy & Astrophysics, Professor Megan Urry says.

Astronomers believe that the dimming is caused by the quasar's black hole, which may now be consuming less energy, thus giving off less energy in the process.  Over the last six years, the quasar has dimmed by an order of seven magnitudes.

"This is like a dimmer switch," coauthor, Stephanie LaMassa says. "The power source just went dim. Because the life cycle of a quasar is one of the big unknowns, catching one as it changes, within a human lifetime, is amazing."

Researchers believe the new study, published in Astrophysical Journal, will help them better understand the lifecycle of black holes and quasars, and they hope that it will provide new insights into how our galaxy came to be the way it is today.

"It makes a difference to know how black holes grow," Urry says. "This perhaps has implications for how the Milky Way looks today."

"Even though astronomers have been studying quasars for more than 50 years," LaMassa says, "it's exciting that someone like me, who has studied black holes for almost a decade, can find something completely new."

But researchers came upon this new discovery simply by accident.  At the time, they were just studying quasar data when they happened to come across one with broad emission lines that appeared to be dramatically weaker than they expected.

The first quasars were first noted in the 1950's by a pair of American astronomers, Allan Sandage and Thomas Matthews.  At the time, the objects were originally recorded as radio signals with no known visible sources.

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