Some supermassive black holes rapidly consume surrounding matter while simultaneously firing powerful streams of plasma into space at nearly the speed of light. However, this creates a physical puzzle: rapid feeding is expected to form a cold, flat accretion disk around the black hole, which prevents powerful jets from forming.

A research team led by Associate Professor Hirofumi Noda of Tohoku University and Associate Professor Kazuhiro Hada of Nagoya City University has now found evidence that helps resolve this mystery. By combining observations from the X-Ray Imaging and Spectroscopy Mission (XRISM) with international networks of radio and millimeter telescopes, the team identified the conditions that allow a rapidly feeding supermassive black hole to launch a powerful relativistic jet.

"By looking at the same black hole with state-of-the-art X-ray and radio telescopes, we were able to see both the hot plasma surrounding the black hole and the jet emerging from it," says Noda. "This allows us to directly connect the extreme environment near the black hole with the formation of the jet."

The team observed 3C 120, an active galaxy located in the constellation Taurus that hosts a supermassive black hole rapidly accreting matter while launching a powerful jet. XRISM detected an iron emission line from the accretion disk surrounding the black holeF. The shape of this line is distorted by the effects of Einstein's general relativity, allowing the researchers to determine how close the disk extends toward the black hole.

The observations indicate that the cold, relatively flat accretion disk ends at about 20 times the black hole's radius. Beyond this point, it transitions into a hot flow of plasma reaching hundreds of millions of degrees. At the same time, radio and millimeter observations using the Global Millimeter VLBI Array, Very Long Baseline Array and East Asian VLBI Network traced the narrowing jet back to its origin within this hot flow, close to the black hole.

This hot environment can allow magnetic fields to accumulate around the black hole. These magnetic fields are thought to extract some of the rotational energy of the black hole and channel it into a powerful jet. The observations therefore demonstrate that 3C 120 satisfies the conditions required for this mechanism to operate, providing new insight into how rapidly feeding supermassive black holes can produce relativistic jets.

The findings also offer a new way to study the immediate surroundings of supermassive black holes. The team is conducting further coordinated observations of a more massive black hole using XRISM and global radio observatories, while comparing the results with theoretical models and computer simulations.

"Our next goal is to build a more complete picture of how matter, magnetic fields and black hole rotation interact in these extreme environments," adds Noda. "Understanding this process may also help us better understand how supermassive black holes influence the evolution of galaxies and the larger structures of the Universe."

Details of the study were published in the journal Astrophysical Journal Letters on October 19, 2026.