Neutron Star Merger Sent Jet Shooting Through Space at Almost the Speed of Light

A simulation shows one of the most violent events in the universe: a pair of neutron stars colliding and merging. NASA Goddard

A colossal neutron star merger in a galaxy 130 million light-years away didn't just send game-changing gravitational waves undulating through space. Radio observations of the explosive event have revealed a thin jet of particles burst from the collision and shot through space at nearly the speed of light.

The findings, published in Nature, are exciting for astronomers because these jets are thought to produce gamma-ray bursts—mysterious, incredibly bright explosions of light. Scientists thought explosive neutron mergers should cause the phenomenal bursts—and these jets provide an important link.

Scientists probing radio signals from the collision noticed that part of the emission had shifted so quickly that nothing but a jet could explain the movement. Measurements revealed a motion that appeared four times faster than light, Kunal Mooley, of the National Radio Astronomy Observatory and Caltech, said in a statement. "That illusion, called superluminal motion, results when the jet is pointed nearly toward Earth and the material in the jet is moving close to the speed of light."

These speedy particles are charging through space at in a "very narrow" jet no more than five degrees wide, Adam Deller, of the Swinburne University of Technology and formerly of the NRAO, added. "But to match our observations, the material in the jet also has to be blasting outwards at over 97 percent of the speed of light."

One explanation of the explosive merger suggested the colliding neutron stars released a shell of debris when they slammed together, creating an expanding cocoon of material. "Our interpretation is that the cocoon dominated the radio emission until about 60 days after the merger, and at later times the emission was jet dominated," Ore Gottlieb, of Tel Aviv University, said in a statement.

Scientists were "incredibly lucky" to observe such an impressive cosmic event, Gregg Hallinan of Caltech added. "If the jet had been pointed much farther away from Earth, the radio emission would have been too faint for us to detect."

"Jets are enigmatic phenomena seen in a number of environments," Joe Pesce, National Science Foundation program director for the National Radio Astronomy Observatory, said in the statement. "These exquisite observations in the radio part of the electromagnetic spectrum are providing a fascinating insight into them, helping us understand how they work."