The world’s first observation of a lightyear-scale black hole gas flow

Giant black holes suck up galactic gas toward their center and eventually discard much of it, Japanese researchers have found in a study they describe as “monumental.”

In an image that evokes a child getting most of its food from its face, bib and arms, rather than its mouth, these large gravity wells spread throughout the universe were discovered using only a small amount of gas drawn into their spaces.

This discovery was made in a detailed study of the constellation Circinus, about 13 million light-years away, with the Atacama Large Millimeter/submillimeter Array (ALMA) telescope.

At the heart of Circinus are two black holes – one massive, ‘eating’ nearby gas from the surrounding galaxy.

Under the black hole’s gravity, these gases reach incredible speeds, causing particles to collide, burn, and emit light so intense that it can be seen with telescopes millions of light-years away.

Super black holes live by the “reuse, recycle” mantra

Now, for the first time, a team led by assistant professor of the National Astronomical Observatory of Japan Takuma Izumi measured the nature and behavior of the gas around these black hole events – known as active galactic nuclei – on a small scale, one year.

The center of the Circinus Galaxy observed with ALMA. Distribution of carbon monoxide (CO; indicating the presence of medium molecular gas), atomic carbon (C; indicating the presence of atomic gas), hydrogen cyanide (HCN; indicating the presence of high molecular density gas), and the hydrogen recombination line (H36α; indicating the presence of ionized gas), shown in red, blue, green, and pink, respectively. There is an active galactic nucleus in the center. This galaxy is known to have a tilted structure from the outer to the inner regions, with the central region resembling an almost edge-on disk. The size of the thick central gas disk (green) is about 6 light-years: this was clearly seen thanks to the high resolution of ALMA (see inset for a zoom view). The plasma outflow moves almost perpendicular to the central dense disk. Credit: ALMA (ESO/NAOJ/NRAO), T. Izumi et al.

It is an amazing achievement considering that such measurements were of very small resolutions, covering 100-100,000s of light years.


Their investigation found gas near the center of the black hole. Accretion discs – often thought of by astronomers as swirling objects being absorbed into the black hole’s dark core – are subject to massive gravitational forces, causing them to collapse and gas to be pulled in quickly.

Illustration showing interstellar gas being pulled in and out of a black hole
Figure showing the distribution of gas in the active galactic nucleus of Circinus. Credit: ALMA (ESO/NAOJ/NRAO), T. Izumi et al.

And the accretion rate that gives off gas to a black hole is 30 times what is needed for matter to grow. These calculations, and their observations, show that the accreted money is thrown back as molecular or atomic gas, where it rejoins the accretion disc and the process begins again.

Izumi’s team likens this process to a water fountain, where water is spat out and caught in a basin below to be reused. However, having only studied this phenomenon in relation to the Circinus galaxy, Izumi hopes to refine the research data by using ALMA to examine supermassive black holes.

“Seeing the flow and outflow of space just a few light-years away from an accreting black hole, especially in multiphase gas, and even determining the mechanism of the expansion itself, is a major achievement in the history of the largest black hole study,” Izumi said.

“But to better understand the growth of supermassive black holes in cosmic history, we need to investigate different types of black holes that are far away from us.”

Support the cosmos today

Cosmos is a non-profit science newsroom that provides free access to thousands of articles, podcasts and videos every year. Help us keep it that way. Support our work today.