Never-Before-Seen Cosmic Weather Event Was Witnessed by Astronomers

Black holes can get “rained” on.

An international team of astronomers has just witnessed a never-before-seen cosmic weather event: a cluster of intergalactic gas clouds “raining” into a supermassive black hole at the center of an elliptical galaxy known as Abell 2597.

Using the Atacama Large Millimeter/submillimeter Array (ALMA) located in northern Chile, the team detected direct evidence in Abell 2597, located one billion light-years from Earth, that cold dense gas clouds can merge out of hot intergalactic gas, before plummeting towards the center of a galaxy’s supermassive black hole.

Supermassive black holes feed through a process known as accretion (the gradual accumulation of material), but the new discovery has astronomers rethinking current views of this process.

SEE ALSO: You Could Spot a Black Hole With Your Hobby Telescope

Previously, astronomers believed that in large galaxies, supermassive black holes fed predominantly on hot ionized gas from the galaxy’s halo — the roughly spherical part of a galaxy which extends beyond what is visible. But according to the new ALMA observations, with the right intergalactic weather conditions — a particular combination of cooling, heating, and turbulence — black holes can also feast on a downpouring of giant, cold clouds of molecular gas.

"This so-called cold, chaotic accretion has been a major theoretical prediction in recent years, but this is one of the first unambiguous pieces of observational evidence for a chaotic, cold 'rain' feeding a supermassive black hole," Grant Tremblay, an astronomer with Yale University, and lead author on the paper appearing in the journal Nature, said in an ESO news release.

"It's exciting to think we might actually be observing this galaxy-spanning 'rainstorm' feeding a black hole whose mass is about 300 million times that of our Sun," Tremblay continued.

Near the center of the galaxy, the researchers discovered that three massive clumps of cold gas, each containing as much material as a million suns, were showering toward the supermassive black hole’s core at roughly 670,000 miles per hour (300 kilometers per second). Normally, objects at this distance and scale would be nearly impossible to distinguish. However, the individual clumps were spotted by billion light-year-long “shadows” they casted towards Earth.

^{Photo credit: B. Saxton (NRAO/AUI/NSF); G. Tremblay et al.; NASA/ESA Hubble; ALMA (ESO/NAOJ/NRAO). Image has been cropped}

Caption: Box shows the "shadow" (black) produced by the absorption of the light emitted by electrons. The shadow indicates that cold clouds of molecular gas are raining in on the black hole.

These shadows, known as absorption features, were formed by the gas clouds blocking out a portion of light emitted by electrons circling around the magnetic fields close to the supermassive black hole’s center. Even though ALMA was only able to detect three of these clumps, the astronomers believe that there may be thousands of them in the area, which will likely continue to fuel the supermassive black hole for quite some time.

To determine if this kind of cosmic weather is as common as theory suggests, the astronomers will continue to use ALMA to search for more “rainstorms” in other galaxies.

You might also like: A Group of Black Holes Were Discovered Mysteriously Spinning in the Same Direction