Quasar winds are crucial to galaxy formation, scientists say
Artist's illustration of turbulent winds of gas swirling around a black hole. Some of the gas is spiraling inward, but some is being blown away. Photo credit: NASA, and M. Weiss (Chandra X -ray Center)
At the heart of just about every galaxy, including our own Milky Way, there's a supermassive black hole—some of which are actively devouring "torn-apart stars, dust, rocks, planets, and anything that gets too close," Jesse Rogerson, a PhD candidate at York University in Toronto, told me. This violent and energetic process produces winds so powerful they'd rip your face off if you got too close.
In new research, Rogerson describes the fastest winds ever recorded at a supermassive black hole, which were seen at ultraviolet wavelengths: winds coursing through space at 20 per cent the speed of light, more than 125 million miles per hour, "equivalent to a category 77 hurricane," he said.
Rogerson studies quasars, the discs of hot gas that form around supermassive black holes. "They're monsters, millions or billions of times the mass of the sun," he told me.
"As material is falling towards the black hole, and onto it, it makes this really bright disk," Rogerson explained, and produces extraordinary amounts of energy. (Maybe luckily for us, the supermassive black hole at the center of the Milky Way galaxy is quiet for now.) Quasars are the brightest objects in the universe, although because they're so distant from us, they can't be spotted with the naked eye.
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To make his observations, Rogerson and his team started out with data from the Sloan Digital Sky Survey, finding 300 possible candidates, then narrowed them down to 100 to study further with the Gemini Observatory in Hawaii and Chile. (Canada is one of six countries that partner in Gemini.)
As for the high-velocity winds produced at this supermassive black hole, "imagine being blasted just by heat, and that heat pushing you," Rogerson said.
Quasar winds are important to galaxy formation, he continued. "It's spitting stuff back out into the galaxy, even disrupting the star formation process." If these winds were less forceful, or didn't exist at all, big galaxies would have lots more stars than they do, Rogerson said. Supermassive black holes shape the galaxies they live in.
Once these monsters have devoured everything nearby, Rogerson said, they stabilize, burning out like a forest fire that runs out of fuel. But what happens to all the stuff that got sucked inside? Scientists have no idea. "Your guess is as good as mine."