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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.

"Our continued radio monitoring has confirmed that all this emission was produced by a cocoon. This event, therefore, does not provide direct confirmation of the link between neutron star mergers and GRBs [gamma ray bursts]," Caltech astronomer and study coauthor Gregg Hallinan tells Axios.

The evidence: A jet emission of X-rays and radio waves would be expected to get weaker over time if it was being viewed on Earth from an angle, as researchers originally proposed after observing this particular event — but astronomers report the intensity of the radio waves continued to grow up to 93 days later. They propose the jet could be colliding with surrounding material to create a cocoon that can send light in many directions. This could account for the radio and gamma ray emissions they see.

Yes, but: "The tension is between whether or not you can uniquely explain the observations using this cocooony thing, or whether you can still explain the observation just with a jet with more complexity built into the physics," Daryl Haggard, assistant professor of physics at McGill University, told Gizmodo's Ryan Mandelbaum. "That is completely unresolved."

Go deeper

Mike Allen, author of AM
52 mins ago - Politics & Policy

Fauci fires back at Rand Paul for slam on tonight's "Axios on HBO"

Responding to charges by Sen. Rand Paul on Sunday's "Axios on HBO," NIAID director Anthony Fauci told "ABC This Week" that it's "molecularly impossible" for U.S.-funded bat virus research in China to have produced COVID-19.

Why it matters: The issue 0f Wuhan research was reignited on the right last week with a National Institutes of Health letter to Congress disclosing more about the research.

Manchin, Schumer huddle with Biden in Delaware to discuss spending bill

Senate Majority Leader Chuck Schumer (L) and Sen. Joe Manchin (R) at the U.S. Capitol on Nov. 13, 2014. Photo: Win McNamee/Getty Images

Sen. Joe Manchin (D-W.Va.) will meet with President Biden and Senate Majority Leader Charles Schumer (D-N.Y.) on Sunday morning in Delaware as Democrats look to reach an agreement on the massive spending measure.

Driving the news: Democrats are still negotiating what to keep in the bill and how to pay for it, with Biden saying on Thursday that the party does not have the votes to raise the corporate tax rate.

3 hours ago - Technology

Scoop: Facebook exec warns of "more bad headlines"

Illustration: Megan Robinson/Axios

In a post to staffers Saturday obtained by Axios, Facebook VP of global affairs Nick Clegg warned the company that worse coverage could be on the way: “We need to steel ourselves for more bad headlines in the coming days, I’m afraid.”

Catch up quick: Roughly two dozen news outlets had agreed to hold stories based on leaked materials from Facebook whistleblower Frances Haugen for Monday publication — but the embargo fell apart Friday night as participating newsrooms posted a batch of articles ahead of the weekend.