Nav: Home

Black hole is producing its own fuel for star-making

February 14, 2017

The Phoenix cluster is an enormous accumulation of about 1,000 galaxies, located 5.7 billion light years from Earth. At its center lies a massive galaxy, which appears to be spitting out stars at a rate of about 1,000 per year. Most other galaxies in the universe are far less productive, squeaking out just a few stars each year, and scientists have wondered what has fueled the Phoenix cluster's extreme stellar output.

Now scientists from MIT, the University of Cambridge, and elsewhere may have an answer. In a paper published today in the Astrophysical Journal, the team reports observing jets of hot, 10-million-degree gas blasting out from the central galaxy's black hole and blowing large bubbles out into the surrounding plasma.

These jets normally act to quench star formation by blowing away cold gas -- the main fuel that a galaxy consumes to generate stars. However, the researchers found that the hot jets and bubbles emanating from the center of the Phoenix cluster may also have the opposite effect of producing cold gas, that in turn rains back onto the galaxy, fueling further starbursts. This suggests that the black hole has found a way to recycle some of its hot gas as cold, star-making fuel.

"We have thought the role of black hole jets and bubbles was to regulate star formation and to keep cooling from happening," says Michael McDonald, assistant professor of physics in MIT's Kavli Institute for Astrophysics and Space Research. "We kind of thought they were one-trick ponies, but now we see they can actually help cooling, and it's not such a cut-and-dried picture."

The new findings help to explain the Phoenix cluster's exceptional star-producing power. They may also provide new insight into how supermassive black holes and their host galaxies mutually grow and evolve.

McDonald's co-authors include lead author Helen Russell, an astronomer at Cambridge University; and others from the University of Waterloo, the Harvard-Smithsonian Center for Astrophysics, the University of Illinois, and elsewhere.

Hot jets, cold filaments

The team analyzed observations of the Phoenix cluster gathered by the Atacama Large Millimeter Array (ALMA), a collection of 66 large radio telescopes spread over the desert of northern Chile. In 2015, the group obtained permission to direct the telescopes at the Phoenix cluster to measure its radio emissions and to detect and map signs of cold gas.

The researchers looked through the data for signals of carbon monoxide, a gas that is present wherever there is cold hydrogen gas. They then converted the carbon monoxide emissions to hydrogen gas, to generate a map of cold gas near the center of the Phoenix cluster. The resulting picture was a puzzling surprise.

"You would expect to see a knot of cold gas at the center, where star formation happens," McDonald says. "But we saw these giant filaments of cold gas that extend 20,000 light years from the central black hole, beyond the central galaxy itself. It's kind of beautiful to see."

The team had previously used NASA's Chandra X-Ray Observatory to map the cluster's hot gas. These observations produced a picture in which powerful jets flew out from the black hole at close to the speed of light. Further out, the researchers saw that the jets inflated giant bubbles in the hot gas.

When the team superimposed its picture of the Phoenix cluster's cold gas onto the map of hot gas, they found a "perfect spatial correspondence": The long filaments of frigid, 10-kelvins gas appeared to be draped over the bubbles of hot gas.

"This may be the best picture we have of black holes influencing the cold gas," McDonald says.

Feeding the black hole

What the researchers believe to be happening is that, as jet inflate bubbles of hot, 10-million-degree gas near the black hole, they drag behind them a wake of slightly cooler, 1-million-degree gas. The bubbles eventually detach from the jets and float further out into the galaxy cluster, where each bubble's trail of gas cools, forming long filaments of extremely cold gas that condense and rain back onto the black hole as fuel for star formation.

"It's a very new idea that the bubbles and jets can actually influence the distribution of cold gas in any way," McDonald says.

Scientists have estimated that there is enough cold gas near the center of the Phoenix cluster to keep producing stars at a high rate for another 30 to 40 million years. Now that the researchers have identified a new feedback mechanism that may supply the black hole with even more cold gas, the cluster's stellar output may continue for much longer.

"As long as there's cold gas feeding it, the black hole will keep burping out these jets," McDonald says. "But now we've found that these jets are making more food, or cold gas. So you're in this cycle that, in theory, could go on for a very long time."

He suspects the reason the black hole is able to generate fuel for itself might have something to do with its size. If the black hole is relatively small, it may produce jets that are too weak to completely blast cold gas away from the cluster.

"Right now [the black hole] may be pretty small, and it'd be like putting a civilian in the ring with Mike Tyson," McDonald says. "It's just not up to the task of blowing this cold gas far enough away that it would never come back."

The team is hoping to determine the mass of the black hole, as well as identify other, similarly extreme starmakers in the universe.
-end-
Additional background

PAPER: ALMA observations of massive molecular gas filaments encasing radio bubbles in the Phoenix Cluster http://iopscience.iop.org/article/10.3847/1538-4357/836/1/130

ARCHIVE: Scientists observe supermassive black hole feeding on cold gas http://news.mit.edu/2016/scientists-observe-supermassive-black-hole-feeding-cold-gas-0608

ARCHIVE: Most distant galaxy cluster identified http://news.mit.edu/2016/most-distant-massive-galaxy-cluster-identified-0107

ARCHIVE: Why isn't the universe as bright as it should be? http://news.mit.edu/2015/galaxies-regulate-stars-0304

ARCHIVE: Most massive and luminous galaxy cluster identified http://news.mit.edu/2012/cool-luminous-galaxy-cluster-identified-0815

Massachusetts Institute of Technology

Related Black Hole Articles:

Scientists make waves with black hole research
Scientists at the University of Nottingham have made a significant leap forward in understanding the workings of one of the mysteries of the universe.
Collapsing star gives birth to a black hole
Astronomers have watched as a massive, dying star was likely reborn as a black hole.
When helium behaves like a black hole
A team of scientists has discovered that a law controlling the bizarre behavior of black holes out in space -- is also true for cold helium atoms that can be studied in laboratories.
Star in closest orbit ever seen around black hole
Astronomers have found evidence of a star that whips around a likely black hole twice an hour.
Tail of stray black hole hiding in the Milky Way
By analyzing the gas motion of an extraordinarily fast-moving cosmic cloud in a corner of the Milky Way, Astronomers found hints of a wandering black hole hidden in the cloud.
Hubble gazes into a black hole of puzzling lightness
The beautiful spiral galaxy visible in the center of the image is known as RX J1140.1+0307, a galaxy in the Virgo constellation imaged by the NASA/ESA Hubble Space Telescope, and it presents an interesting puzzle.
Clandestine black hole may represent new population
Astronomers have combined data from NASA's Chandra X-ray Observatory, the Hubble Space Telescope and the National Science Foundation's Karl G.
When will a neutron star collapse to a black hole?
Astrophysicists from Goethe-University Frankfurt have found a simple formula for the maximum mass of a rotating neutron star and hence answered a question that had been open for decades.
Behemoth black hole found in an unlikely place
Astronomers have uncovered a near-record breaking supermassive black hole, weighing 17 billion suns, in an unlikely place: in the center of a galaxy in a sparsely populated area of the universe.
Behemoth black hole found in an unlikely place
Astronomers have uncovered one of the biggest supermassive black holes, with the mass of 17 billion Suns, in an unlikely place: the centre of a galaxy that lies in a quiet backwater of the Universe.

Related Black Hole Reading:

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Jumpstarting Creativity
Our greatest breakthroughs and triumphs have one thing in common: creativity. But how do you ignite it? And how do you rekindle it? This hour, TED speakers explore ideas on jumpstarting creativity. Guests include economist Tim Harford, producer Helen Marriage, artificial intelligence researcher Steve Engels, and behavioral scientist Marily Oppezzo.
Now Playing: Science for the People

#524 The Human Network
What does a network of humans look like and how does it work? How does information spread? How do decisions and opinions spread? What gets distorted as it moves through the network and why? This week we dig into the ins and outs of human networks with Matthew Jackson, Professor of Economics at Stanford University and author of the book "The Human Network: How Your Social Position Determines Your Power, Beliefs, and Behaviours".