Black Hole Fires at Neighboring Galaxy

Newswise — A powerful jet from a supermassive black hole is blasting a nearby galaxy, according to new results from NASA. This galactic violence, never seen before, could have a profound effect on any planets in the path of the jet and trigger a burst of star formation in the wake of its destruction.

Known as 3C321, the system contains two galaxies in orbit around each other. Chandra X-ray Observatory data show that both galaxies contain supermassive black holes at their centers, but the larger galaxy has a jet emanating from the vicinity of its black hole. The smaller galaxy has apparently swung into the path of this jet.

This "death star galaxy" was discovered through the combined efforts of both space and ground-based telescopes. NASA's Chandra, Hubble Space Telescope, and Spitzer Space Telescope, plus the Very Large Array (VLA) and MERLIN radio telescopes were required for this result.

"We've seen many jets produced by black holes, but this is the first time we've seen one punch into another galaxy like we're seeing here," said Dan Evans, the leader of the study from the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass. "This jet could be causing all sorts of problems for the smaller galaxy it is pummeling."

Jets from supermassive black holes produce giant amounts of radiation, especially high-energy X-rays and gamma-rays, which can be lethal in large quantities. The combined effects of this radiation and particles traveling at almost the speed of light could severely damage the atmospheres of any planets lying in the path of the jet. For example, protective layers of ozone in the upper atmosphere of planets could be destroyed.

Jets produced by supermassive black holes transport enormous amounts of energy far from the black holes and enable them to affect matter on scales vastly larger than the size of the black hole. For this reason, understanding the properties of jets is a key goal for astrophysical research.

"We see jets all over the Universe, but we're still struggling to understand some of their basic properties," said co-investigator Martin Hardcastle of the University of Hertfordshire, United Kingdom. "This system of 3C321 gives us a chance to learn how they're affected when they slam into something - like a galaxy - and what they do after that." The effect of the jet on the companion galaxy is likely to be substantial, because the galaxies in 3C321 are extremely close to one another. At only about 20,000 light years apart, these galaxies lie approximately the same distance as the Earth is from the center of the Milky Way.

A bright spot in the VLA and MERLIN images shows where the jet has struck the side of the galaxy, dissipating some of its energy. After striking the galaxy, the jet has been disrupted and deflected.

"This is a fascinating result, and we can be glad that we're seeing it from a safe distance," said Neil Tyson, an astrophysicist from American Museum of Natural History in New York, who is not part of the research team. "Knowing how lethal the radiation from the jet could be, I wouldn't want to be anywhere near its line of fire."

Another unique aspect of the discovery in 3C321 is this event is relatively short-lived on cosmic scales. Features seen in the VLA and Chandra images indicate that the jet began impacting the galaxy about one million years ago, a small fraction of the system's lifetime. This means that such an alignment is quite rare in the nearby Universe, making 3C321 an important opportunity to study such a phenomenon.

It is possible that it would not all be bad news for the galaxy being struck by the jet. The massive influx of energy and radiation from the jet may induce the formation of large numbers of stars and planets once its initial wake of destruction is complete.

The results from Evans and his colleagues will appear in The Astrophysical Journal. NASA's Marshall Space Flight Center, Huntsville, Ala., manages the Chandra program for the agency's Science Mission Directorate. The Smithsonian Astrophysical Observatory controls science and flight operations from the Chandra X-ray Center in Cambridge, Mass.