12.01.2026

Rare, powerful jet strips star-forming gas from its host, offering new insight into how galaxies evolve

This artist’s rendering illustrates a precessing jet erupting from the supermassive black hole at the center of galaxy VV 340a. Optical observations from the W. M. Keck Observatory revealed extended, cooler gas pushed outward over thousands of light-years, while infrared data from NASA’s James Webb Space Telescope captured the super-heated coronal gas near the galaxy’s core. Credit: W. M. Keck Observatory / Adam Makarenko

Maunakea, Hawaiʻi – Astronomers using W. M. Keck Observatory on Maunakea, Hawaiʻi Island have uncovered the largest and most extended stream of super-heated gas ever observed flowing from a nearby galaxy, providing the clearest evidence yet that a supermassive black hole can dramatically reshape its host galaxy far beyond its core.

The discovery centers on galaxy VV 340a, where observations revealed vast structures of energized gas stretching up to 20,000 light-years from the galaxy’s center — far beyond what has ever been seen before. The findings, led by researchers at the University of California, Irvine and the California Institute of Technology/IPAC, are published in Science.

Critical observations from the Keck Cosmic Web Imager (KCWI) on the Observatory’s Keck II telescope traced cooler, lower-energy gas extending well outside the galaxy’s disk. This gas forms a striking, spear-like structure aligned with the galaxy’s center, providing a fossil record of prolonged activity driven by the galaxy’s central supermassive black hole.

“The Keck Observatory data is what allowed us to understand the true scale of this phenomenon,” said lead author Justin Kader, a UC Irvine postdoctoral researcher. “The gas we see with Keck Observatory reaches the farthest distances from the black hole, which means it also traces the longest timescales. Without these observations, we wouldn’t know how powerful — or how persistent — this outflow really is.”

The data obtained from KCWI were essential for modeling how much material is being expelled and determining whether the outflow is capable of altering the galaxy’s future. The answer, the team found, is yes.

A Jet with Enough Power to Halt Star Formation

The team combined Keck Observatory’s optical data with infrared observations from NASA’s James Webb Space Telescope and radio images from the Karl G. Jansky Very Large Array (VLA) to build a complete picture of the system.

At the galaxy’s center, Webb detected intensely energized “coronal” gas, plasma heated to extreme temperatures, erupting from either side of the black hole. While such gas is typically confined to regions just hundreds of parsecs across, in VV 340a it stretches for several thousands of parsecs, making it the most extended coronal gas structure ever observed.

The VLA radio data revealed that a pair of plasma jets, launched by the black hole, twist into a helical, S-shaped pattern as they move outward — evidence of a rare phenomenon known as jet precession, in which the jet’s direction slowly wobbles over time.

“This is the first time we’ve seen a precessing, kiloparsec-scale radio jet driving such a massive outflow in a disk galaxy,” Kader said.

While Webb’s infrared vision revealed the energetic heart of the system, Keck Observatory’s observations showed how that energy propagates outward, coupling with the surrounding galaxy and dragging gas along in its wake.

The KCWI data demonstrates that as the jet slows, it entrains cooler material, pushing it outward at lower speeds. This process strips the galaxy of gas at a rate equivalent to forming nearly 20 suns every year, dramatically suppressing future star formation.

A Surprise in an Unexpected Galaxy

Perhaps most surprising is where this activity is happening. Powerful, precessing jets are usually found in old, elliptical galaxies which have stopped star formation, not in relatively young, star-forming spiral galaxies like VV 340a, which is still in the early stages of a merger with another galaxy.

The discovery challenges long-standing ideas about how galaxies and their central black holes evolve together and raises the possibility that similar events could occur in galaxies like our own Milky Way.

“There’s no clear fossil record of something like this happening in our galaxy, but this discovery suggests we can’t rule it out,” Kader said. “It changes the way we think about the galaxy we live in.”

Looking Ahead

The team plans to pursue deeper, higher-resolution radio observations to determine whether a second supermassive black hole may be causing the jet’s wobble, a potential first step toward identifying a binary black hole system.

“We’re only beginning to understand how common this kind of activity may be,” Vivian U, an associate scientist at Caltech/IPAC and the second and senior author of the study, said. “With Keck Observatory and these other powerful observatories working together, we’re opening a new window into how galaxies change over time.”

Quelle: W. M. Keck Observatory