Artist's rendering of a very distant quasar powered by a black hole (Credit: ESO/M. Kornmesser)

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.

In a new development, astronomers from Yale University have discovered a strange quasar that appears to be flipping a dimming switch, and they believe this discovery will provide insight into how quasars form and evolve.

The work, which is set to be published in an upcoming edition of the Astrophysical Journal, describes the quasar in question and how the team happened upon it. Essentially, one of the researchers — Stephanie LaMassa, a Yale associate research scientist — found it by accident. While pouring through data collected by Stripe 82  — a probe that maps the small portion of sky along the celestial equator, its data is used for projects like the Sloan Digital Sky Survey — an extremely distant, but still noticeable, quasar came to her attention, but the quasar itself wasn't the most fascinating part.

In fact, astronomers have known about this quasar for a while, yet the latest round of observations reveal that it has dimmed significantly... by a factor of 6 or 7. What's more is that there were significant changes in its broad emission lines, or the spectra of the quasar's cool gas supply. Generally speaking, the hot gas far exceeds the cold. To reiterate, quasars form when black holes have more material falling in than they can consume, which results in the material building up around them a traffic jam; the further inward, the hotter the gas is (and the more brightly in shines), the farther you go out, the cooler the gas becomes. However, it's still not impervious to the allure of black holes. Indeed, even when it's far out (by our standards anyway), incoming matter can still energize it.

With this quasar, the broad emission lines weakened so dramatically, it's clear that something changed with its inner dynamics. The team suggests that the object went on a diet, consuming far less matter than it was during previous observations. Subsequently, its broad emission lines basically disappeared overnight (again, by our standards).

This artist's rendering shows the quasar at full brightness. (Credit: Michael Helfenbein/Yale University)

"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."

Of course, they explored other options too, namely looking at whether other phenomena — obscuring clouds of dust, or another object transiting it at exactly the right time — could be responsible for the extreme change, but follow-up observations carried out at different wavelengths only strengthened their discovery.

Now, we can use it to better understand these mysterious objects, perhaps even shedding light on what turns them on in the first place.. Not to mention, we still haven't figured out why they are only found in the distant reaches of space, having been born a billion years or so after the big bang.

"It makes a difference to know how black holes grow," said C. Megan Urry, the study's principal investigator, "noting that all galaxies have black holes, and quasars are a phase that black holes go through before becoming dormant." "This perhaps has implications for how the Milky Way looks today," she continued.

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


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