On December 11, 2021, a beam of gamma rays — the most energetic form of light — slammed into NASA’s Swift satellite. Within 120 seconds, the satellite had swiveled toward the blast and spotted the glowing embers of a cosmic catastrophe. Ten minutes later, alerts went out to astronomers around the world.
Among them was Jillian Rastinejad, a graduate student at Northwestern University. To Rastinejad and her collaborators, this gamma-ray burst looked oddly similar to an unusual burst from 2006. Rastinejad called up the Gemini Observatory in Hawai‘i and enlisted researchers there to stare deeply at the patch of sky where the burst had come from. A few days later, when clouds rolled in, a researcher at the MMT Observatory in Arizona took over, doing her best to keep the telescope trained on the fading spot of light a billion light-years away.
It was no small feat given that the weather was turning there too, Rastinejad said. “She found a hole in the clouds for us around 4 a.m. every day.”
By the time the chain of observations had wrapped up a week or so later, Rastinejad and her colleagues had a pretty good idea of what had fired those gamma rays across the universe. As they’d watched, the burst’s aftermath had turned redder and redder — an unmistakable sign that in the debris, heavy atoms like gold and platinum were being forged. The main source of such cosmic alchemy is collisions involving neutron stars, the unimaginably dense cores of dead suns.
The only problem was that such a conclusion seemed impossible. When neutron stars merge, astrophysicists suspect, it’s all over in a fraction of a second. But Swift had recorded a gamma-ray bombardment lasting a relatively interminable 51 seconds — normally the signature of a very different type of cosmic drama.
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