Supermassive black holes have long puzzled astronomers, particularly how they grow so large.
An international team of astronomers, including researchers from Chalmers University of Technology in Sweden, has made a breakthrough discovery.
They found a powerful rotating, magnetic wind that may help a galaxy’s central supermassive black hole grow.
This discovery was made with the help of the ALMA telescope, observing the nearby galaxy ESO320-G030, and is detailed in the journal Astronomy and Astrophysics.
Supermassive black holes reside at the center of most galaxies, including our Milky Way.
These objects can be millions or billions of times heavier than the sun. Understanding how they grow so massive is a major question in astronomy.
Mark Gorski (Northwestern University and Chalmers) and Susanne Aalto (Chalmers) led a team to study the galaxy ESO320-G030, located 120 million light years away. This galaxy is very active, forming stars ten times faster than our own Milky Way.
By using the ALMA telescope, the researchers could observe details in the galaxy’s core, hidden behind thick layers of dust and gas.
Aalto, Professor of Radio Astronomy at Chalmers University, explained, “We wanted to measure light from molecules carried by winds from the galaxy’s core, hoping to trace how the winds are launched by a growing, or soon to be growing, supermassive black hole.”
The team focused on light from hydrogen cyanide (HCN) molecules, using ALMA’s ability to capture fine details and track gas movements through the Doppler effect. They discovered patterns suggesting a magnetized, rotating wind.
Unlike other galactic winds that push material away from the black hole, this newly discovered wind seems to feed the black hole, aiding its growth.
“We can see how the winds form a spiraling structure, billowing out from the galaxy’s center,” said Aalto.
“When we measured the rotation, mass, and velocity of the material flowing outwards, we were surprised to find that star formation wasn’t the cause. Instead, the flow may be powered by the inflow of gas and held together by magnetic fields.”
The scientists believe this rotating magnetic wind helps the black hole grow. Material around the black hole forms a chaotic, spinning disk. Magnetic fields in this disk get stronger, helping lift matter away from the galaxy and creating the spiraling wind.
This process slows the spinning disk, allowing more matter to flow into the black hole, increasing its growth.
Gorski noted the similarity to star formation, saying, “Stars in the first stages of their evolution grow with the help of rotating winds, accelerated by magnetic fields. Our observations show that supermassive black holes and stars can grow by similar processes, but on very different scales.”
Gorski, Aalto, and their colleagues plan to study other galaxies to see if this phenomenon is common. “Far from all questions about this process are answered. Now that we know what to look for, the next step is to find out how common this is and what happens next in these galaxies,” said Gorski.
This discovery provides a new perspective on how supermassive black holes grow, potentially solving one of astronomy’s biggest mysteries.
Source: Chalmers University of Technology.
