NASA’s Fermi Gamma-ray Space Telescope "detected none of the high-energy gamma-ray light" from a nearby supernova. NASA explains.
Credit: NASA Goddard Space Flight Center
Credit: NASA Goddard Space Flight Center
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TechTranscript
00:00 NASA's Fermi Gamma-ray Space Telescope
00:04 watches the sky for gamma rays, the highest energy form of light.
00:08 These detections help scientists learn more about the most powerful
00:12 events in the cosmos. However, a recent absence
00:16 of gamma ray detection may have been just as informative.
00:20 Cosmic rays are small particles like protons and helium nuclei
00:24 traveling at nearly the speed of light. It takes a lot of energy to
00:28 accelerate them to that speed, so scientists assume they're driven by
00:32 powerful events like exploding stars, called supernovae.
00:36 Because cosmic rays are charged particles, they interact with magnetic
00:40 fields as they travel. These interactions mean they don't follow a
00:44 straight line from their sources, and so scientists can't trace where they came from.
00:48 But when cosmic rays smash into other particles, they produce gamma rays.
00:52 And gamma rays do travel to us straight from their sources.
00:56 Fermi has even detected such gamma rays from supernova
01:00 remnants, which are thousands of years old.
01:04 If supernovae and their remnants really are a key source of cosmic rays,
01:08 then calculations tell astronomers how many gamma rays Fermi should detect.
01:12 But so far, the telescope hasn't seen enough gamma rays
01:16 from these sources. Scientists had suspected this was
01:20 because the supernovae were too far away, or observations began too late,
01:24 well after peak production.
01:28 In May 2023, Fermi observed the most luminous nearby supernova
01:32 seen since the mission launched 15 years ago. It captured
01:36 data from the first few weeks of the explosion, when scientists anticipated
01:40 the greatest production of cosmic rays. But Fermi didn't see
01:44 any gamma rays from the explosion. Scientists aren't yet
01:48 sure what this means for the link between cosmic rays and supernovae.
01:52 There's still a lot of work left to do. But Fermi's non-detection
01:56 has added a very important new piece to this high-energy puzzle.
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