Black holes often are thought of as just endless pits in space and time that destroy everything they pull toward them.
But new findings confirm the reverse is true, too: Black holes can drive extraordinarily powerful winds that push out and force star formation and shape the fate of a galaxy.
Supermassive black holes are suspected to lurk in the hearts of many—if not all—large galaxies. These holes drag gas inward, which accrues in rapidly spinning, glowing disks.
Astronomers have long thought that such "accretion disks" give off mighty winds that shape the host galaxies, profoundly influencing how they grow.
"In the early universe, galaxies formed from clumps of gas coagulating from mutual gravitational attraction. If unhindered, they would have formed rather bigger structures than what we see today," said astrophysicist Andrew Robinson at the Rochester Institute of Technology in New York. "But if we take into account these winds blowing away surrounding gas, that could help explain the galaxy sizes we see."
Until now, scientists had only theorized that accretion disks launched these winds. No one had actually seen this happen. "These accretion disks are comparable in size to our solar system—big for us, but on the scale of galaxies they're really tiny, and far away to boot, making it virtually impossible to distinguish any details such as winds," Robinson said.
To attempt to observe the winds, Robinson and his colleagues investigated a galaxy roughly 3 billion light years from Earth using the William Herschel Telescope on the Canary Islands off the coast of Africa. At the core of that galaxy lies a quasar, an extremely powerful source of radiation as bright as up to 1 trillion suns that originates from the superheated gas of a black hole's accretion disk.
The researchers discovered that light from the quasar was scattered by electrons in super-fast gas. The specific way in which this light was scattered suggests the gas was rotating at speeds similar to the accretion disk's rate of spin. In other words, they confirmed the accretion disk was launching wind.
The researchers will next try to find out if these disk winds are launched only when the black hole is growing rapidly, or just by quasars, which have the most massive black holes, or by all active galactic nuclei.
The scientists detailed their findings in the Nov. 1 issue of the journal Nature.
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