If a black hole is Voldemort, a quasar is Sauron; Despite being concentrated in an area no larger than our solar system, one, single quasar can outshine our galaxy by a factor of 100, generating more energy in moments than the Sun ever will. However, the mechanism by which they are powered is remarkably simple: at the heart of every quasar is a black hole that has been turbocharged. At least, that’s the working theory anyway.
Until now, scientists have been unable to study both the bright and dim phases of a quasar in a single source. Yale University astronomers have identified the first “changing look” quasar, a gleaming object in deep space that appears to have its own dimmer switch. The discovery may offer a glimpse into the life story of the universe’s great beacons.
Comparison of images from a segment of sky called Stripe 82 taken a few years apart revealed a quasar that dimmed to just one-sixth or one-seventh of its original level during that time.
“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,” C. Megan Urry, a professor of astronomy and astrophysics at Yale University, said.
Stephanie LaMassa, a Yale associate research scientist, noticed the phenomenon during an ongoing probe of Stripe 82 — a sliver of the sky found along the Celestial Equator. Stripe 82 has been scanned in numerous astronomical surveys, including the Sloan Digital Sky Survey.
“This is like a dimmer switch,” LaMassa said. “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.”
A variety of techniques were employed and observations utilized in the analysis of the data, to make certain the observed dimming was not caused by an independent event, such as the passage of a dust cloud between the Earth and quasar.
This exciting discovery may shed more light about our understanding of black holes in relation to the formation of galaxies like the one we have.
“It makes a difference to know how black holes grow,” Urry notes, detailing that every galaxy has a black hole and that quasars are defined as a phase a black holes go through before they go dormant. “This perhaps has implications for how the Milky Way looks today.”
The researchers said they aren’t ruling out the possibility that the first-known “changing look” quasar could fire up again and reverse its recent dimming.
Bottom line: Originally discovered by Thomas Matthews and Allan Sandaeg in the 1950s, the first quasars were first recorded as radio transmissions without a visible source by the pair of American astronomers.
•Astrophysics Journal: https://goo.gl/J03dws.
Press release: https://goo.gl/g7VZyT.