Scientists observe supermassive black hole feeding on cold gas

June 08, 2016

At the center of a galaxy cluster, 1 billion light years from Earth, a voracious, supermassive black hole is preparing for a chilly feast.

For the first time, astronomers have detected billowy clouds of cold, clumpy gas streaming toward a black hole, at the center of a massive galaxy cluster. The clouds are traveling at speeds of up to 355 kilometers per second -- that's almost 800,000 miles per hour -- and may be only 150 light years away from its edge, almost certain to fall into the black hole, feeding its bottomless well. The observations, which will be published in the journal Nature, represent the first direct evidence to support the hypothesis that black holes feed on clouds of cold gas.

The results also suggest that fueling a black hole -- a process known as accretion -- is a whole lot messier than scientists had once thought.

"The simple model of black hole accretion consists of a black hole surrounded by a sphere of hot gas, and that gas accretes smoothly onto the black hole, and everything's simple, mathematically," says Michael McDonald, assistant professor of physics in MIT's Kavli Institute for Astrophysics and Space Research. "But this is the most compelling evidence that this process is not smooth, simple, and clean, but actually quite chaotic and clumpy."

Given the new observations, McDonald says black holes probably have two ways of feeding: For most of the time, they may slowly graze on a steady diet of diffuse hot gas. Once in a while, they may quickly gobble up clumps of cold gas as it comes nearby.

"This diffuse, hot gas is available to the black hole at a low level all the time, and you can have a steady trickle of it going in," McDonald says. "Every now and then, you can have a rainstorm with all these droplets of cold gas, and for a short amount of time, the black hole's eating very quickly. So the idea that there are these two dinner modes for black holes is a pretty nice result."

McDonald is a co-author on the paper, which was led by Grant Tremblay, an astronomer at Yale University.

Seeing shadows

The researchers made their detection using the Atacama Large Millimeter/submillimeter Array, or ALMA -- one of the most powerful telescopes in the world, designed to see the oldest, most distant galaxies in the universe. The team focused ALMA's telescopes 1 billion light years away, on the central galaxy in the Abell 2597 Cluster, a galaxy that is some tens of thousands of light years across. This particular galaxy is among the brightest in the universe, as it is likely producing many new stars.

The team originally wanted to get a sense for how many stars this cluster was churning out, so they mapped all the cold gas within the cluster. This cold gas has cooled and condensed out of the diffuse halo of hot gas surrounding a cluster, forming clumps. It is the collapse of cold gas that creates new stars, especially in the cluster's central galaxy.

"In the center of a cluster, there's a single massive galaxy, the big daddy galaxy of the cluster," McDonald says. "It's sitting at the bottom of a gravitational funnel, and all the gas from a thousand galaxies is available to it. These are the galaxies that are the most massive, with the most massive black holes in the universe, and the most potential for star formation."

The researchers used ALMA to map the spectral signatures, or radio emissions, from the galaxy cluster, looking specifically for signatures of carbon monoxide, the presence of which usually indicates very cold gas, of minus 200 degrees Fahrenheit and below. They mapped carbon monoxide across the entire galaxy cluster and found that as they looked further into the cluster, they encountered progressively cooler gas, from millions of degrees Fahrenheit to subzero temperatures.

At the very center, just at the edge of the cluster's supermassive black hole, the researchers discovered something quite unexpected: the shadows of three very cold, very clumpy gas clouds. The shadows were cast against bright jets of material spewing from the black hole, suggesting that these clouds were very close to being consumed by the black hole.

"We got very lucky," McDonald says. "We could probably look at 100 galaxies like this and not see what we saw just by chance. Seeing three shadows at once is like discovering not just one exoplanet, but three in the first try. Nature was very kind in this case."

A high-energy feast

The team estimated the velocities of the three clouds to be 240, 275, and 355 kilometers per second, with all three headed toward the black hole. McDonald says these three cold gas clouds will likely not stream straight into the black hole but instead be absorbed into its accretion disc -- the massive disc of material that will eventually spiral into the black hole.

He adds that while ALMA was only able to see three clouds of cold gas near the black hole, there may be even more in the vicinity, setting the black hole up for quite a feast.

"We're only seeing this tiny sliver," McDonald says. "If there are three clouds in just our line of sight, there might be millions of clouds all around. And there's a tremendous amount of energy in just these three clouds. So if we were to look at this thing a million years later, we might see that the black hole is in outburst -- much brighter, with more powerful jets, because all this high-energy material is landing on it."
-end-
This research was funded, in part, by NASA, the European Research Council, the Natural Sciences and Engineering Research Council of Canada, and the Science and Technology Facilities Council.

Additional background

ARCHIVE: Most distant massive galaxy cluster identified

ARCHIVE: Why isn't the universe as bright as it should be?

ARCHIVE: Most massive and luminous galaxy cluster identified

Massachusetts Institute of Technology

Related Black Hole Articles from Brightsurf:

Black hole or no black hole: On the outcome of neutron star collisions
A new study lead by GSI scientists and international colleagues investigates black-hole formation in neutron star mergers.

The black hole always chirps twice: New clues deciphering the shape of black holes
A team of gravitational-wave scientists led by the ARC Centre of Excellence for Gravitational Wave Discovery (OzGrav) reveal that when two black holes collide and merge, the remnant black hole 'chirps' not once, but multiple times, emitting gravitational waves--intense ripples in the fabric space and time--that inform us about its shape.

Wobbling shadow of the M87 black hole
New analysis from the Event Horizon Telescope (EHT) Collaboration reveals the behavior of the supermassive black hole in the center of the M87 galaxy across multiple years, indicating the crescent-like shadow feature appears to be wobbling.

How to have a blast like a black hole
Scientists at Osaka University have created magnetized-plasma conditions similar to those near a black hole using very intense laser pulses.

Black hole collision may have exploded with light
Astronomers have seen what appears to the first light ever detected from a black hole merger.

Black hole's heart still beating
The first confirmed heartbeat of a supermassive black hole is still going strong more than ten years after first being observed.

Black hole team discovers path to razor-sharp black hole images
A team of researchers have published new calculations that predict a striking and intricate substructure within black hole images from extreme gravitational light bending.

Planets around a black hole?
Theoreticians in two different fields defied the common knowledge that planets orbit stars like the Sun.

Black hole mergers: Cooking with gas
Gravitational wave detectors are finding black hole mergers in the universe at the rate of one per week.

Going against the flow around a supermassive black hole
At the center of a galaxy called NGC 1068, a supermassive black hole hides within a thick doughnut-shaped cloud of dust and gas.

Read More: Black Hole News and Black Hole Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.