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Another record-breaking quasar with a black hole that’s *too* supermassive
Astronomers have found the most distant quasar yet seen, and, like a handful of others found at this distance, it presents a huge (literally) problem: The black hole powering it is far too big for how long it's been around.
The quasar is named after its coordinates on the sky, J031343.84−180636.4 (let's call it J0313 for short). It was found in a survey of the sky using Pan-STARRS, the Panoramic Survey Telescope and Rapid Response System, a relatively modest 1.8-meter telescope that nonetheless takes very deep images of the heavens, surveying the sky using different filters to get color information on objects. Very distant quasars tend to be bright in the red but emit very little light at blue wavelengths, making them a little bit easier to spot.
Once J0313 was identified as a candidate, the much larger Magellan and Gemini telescopes took a spectrum confirming the immense distance: The light we see from this object traveled over 13 billion years to get here, meaning we see it as it was about 670 million years after the Big Bang itself!
And that's a problem. A quasar is an object we call an active galaxy. Every big galaxy has a supermassive black hole in its core, and in some cases that black hole is actively feeding, gobbling down gas and dust and stars around it. This material forms a huge flat disk around it, which gets infernally hot. It glows so fiercely it can easily outshine the stars in the entire rest of the galaxy combined!
To make matter more intense (again, literally) the magnetic field in the disk winds up into twin vortices, like tornados, which pulls matter from the disk and blasts it away from just outside the black hole. If those beams are pointed more or less in our direction they make the galaxy even brighter. That's what makes the galaxy a quasar.
Given the brightness of J0313 seen and its distance, the astronomers measure its total luminosity — how much energy it gives off — as 36 trillion times the Sun's.
That's... bright. It's nearly three thousand times more luminous than our own Milky Way. Oof.
So what about the supermassive black hole powering all this? In the case of J0313, the deep spectra taken by Magellan reveal the black hole's mass. As the matter swirls around the disk, some of the matter is headed away from us, so its light gets shifted to the red, and some toward us, which gets blue shifted. The amount of this smearing out of colors can be used to determine the mass of the black hole, and the number they got is soul-crushing: 1.6 billion times the mass of the Sun.
We know of lots of black holes with that mass, and some even bigger. But those have had billions of years to grow to that size. At best the one in J0313 is 670 million years old, and in reality somewhat less. How did it grow to such huge proportions so quickly?
This is an ongoing problem in cosmology. We've seen other quasars at roughly this distance, and they also have immense black holes in them, bigger than we think they can get in the short time (galactically speaking) they've been around.
The problem is, black holes can only eat material so quickly. Matter tends to form those disks around them, and the disk is so hot that the radiation it blasts out hits the material falling toward the black hole and blows it away. For a given mass black hole, the rate at which it can eat is balanced by the radiation it emits, called the Eddington Limit. Eat too fast, and it cuts off its own food supply.
That in turn means it's very hard to get a black hole with over a billion solar masses that rapidly. There are several ideas on how to get around this, though. Perhaps smaller black holes form (with thousands or hundreds of thousands of times the Sun's mass) — seed black holes — and these grow rapidly and merge in the nascent galaxy. That can help a lot, though they still have to grow really rapidly.
It's not quite clear how this process works, though. We don't know of very many quasars at this distance (it's a big sky, there aren't many that far away, and it can be difficult to pick them out of a crowded area), but the fact that of the handful we see, they all have huge central black holes means they're growing somehow. I'll note that there may be quasars out there with lower mass black holes and less powerful emission, but they're fainter and harder to find. And finding them would just point out that sure, lower mass black holes can form, but still leaves the problem of how the truly monstrous ones do.
The galaxy itself surrounding the black hole is apparently cranking out stars at a rate a couple of hundred times what the Milky Way is doing, making it what we call a starburst galaxy. That may be tied in with the black hole's mass; lots of material in it to make stars and feed a hungry beast in its core.
Understanding all this is important. For one thing, we know that galaxies and their black holes grow together, so understanding one means understanding the other. But also this informs us on what conditions were like when the Universe was extremely young and still getting its start. On top of that, the light from these distant objects passes by closer objects to us on its way here, and how they affect that light tells us even more about the not-quite-so-distant Universe.
Now that we know it's out there, J0313 will be a prime target for lots of follow-up observations to learn more about it. These quasars pose a big problem, and the more we know about them, the more likely it is we'll figure out the solution.
