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Two stars merge, creating a cocoon and a mystery

An artist's illustration of a "cocoon" in the aftermath of two neutron stars merging. Credit: NRAO/AUI/NSF: D. Berry

The merger of two dense neutron stars millions of years ago produced ripples in spacetime and an afterglow of radiation detected on Earth on August 17. After monitoring the signal for months, a team of astronomers reports today that the X-rays, radio waves and gamma rays emitted from the event may be coming from a cocoon-like structure — the first to be seen.

Why it matters: The origin of short gamma-ray bursts — fast, bright and powerful flashes of radiation from events long ago and far away in the universe — is unknown. A leading theory is they are produced in the merger of neutron stars and black holes that release jets of radiation. The hope then was that observing such jets in an event like researchers did over the summer would confirm the link between neutron star mergers and gamma ray bursts.