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In late 2022, 

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the brightest gamma-ray burst ever seen 
shocked astronomers — 

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and even temporarily blinded
many high-energy detectors in space.

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Now, a study of the first
few minutes of this burst

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have found an important feature
not seen before.

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Gamma-ray bursts are the most
powerful explosions in the cosmos.

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One that occurred October
9th, 2022, was quickly

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dubbed the BOAT, the brightest of all time.

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Events like it may occur in Earth's skies

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only once every 10,000 years.

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As with most gamma-ray bursts,

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the BOAT arose from the death of a massive star.

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When its core ran out of fuel,
it collapsed, creating a black hole

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in the star's center.

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Matter swirled toward the black hole,
and some of it was thrown out

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along two jets moving near the speed of light.

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The jets drilled their way out of the star

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and blasted into space.

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We see a gamma-ray burst
when one of these jets happens

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to point almost directly at Earth.

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That happens somewhere in the sky
almost every day.

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The closer to head on we view a jet,
the brighter it appears.

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This, along with an unusually narrow jet,
is what made the BOAT so exceptional.

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NASA's Fermi Observatory

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carries instruments specifically designed
for studying these explosions.

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Its Gamma-ray Burst Monitor was saturated
by the BOAT’s

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initial flash, but was fine a few minutes later.

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And it's in that data,
around 5 minutes into the event,

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that scientists found something new.

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It's an emission line, a narrow band of enhanced

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brightness in light spread out 
in a spectrum.

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It only lasted 40 seconds,
but it's the first one

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ever seen with high confidence during a burst.

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It gives scientists insight into processes
within parts of the jet,

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where gamma rays — the highest energy
form of light — come from.

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Researchers say it's likely produced by
electrons and their antimatter twins,

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positrons, colliding and annihilating within the jet.

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Each collision produces a pair of gamma rays,
but it also works backwards:

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two gamma rays can collide to form
an electron and a positron.

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In the jet’s environment, both processes occur,

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so there are plenty of particles to go around.

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For this to explain what Fermi saw,

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the gamma rays had to have been shifted
to higher energies by their motion.

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This is similar to a siren rising in pitch
as it races toward us.

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To get that boost, the particles
emitting the gamma-ray line

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must have been moving at 99.9%
the speed of light.

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After decades of studying, GRBs,
scientists know little about the processes

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within these incredible jets, Yet
they're a staple of the cosmos.

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Now, Fermi has given us
 a brief glimpse inside.

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NASA