Fermi Detects First Gamma-Ray Leak From SN 2017egm 440 Million Light-Years Away
Updated
Updated · TechEBlog · May 20
Fermi Detects First Gamma-Ray Leak From SN 2017egm 440 Million Light-Years Away
4 articles · Updated · TechEBlog · May 20
43 to 155 days after SN 2017egm was first spotted in 2017, NASA’s Fermi telescope recorded gamma rays from the supernova—the first clear detection of such emission from a superluminous stellar explosion.
Researchers say the signal points to a newborn magnetar spinning hundreds of times per second, whose particle outflow generated gamma rays inside a dense cloud around the collapsed core.
For roughly 3 months, the expanding debris trapped that high-energy radiation and converted it into the visible light that made SN 2017egm brighter than all stars in its host galaxy combined; later thinning let some gamma rays escape.
Computer models reproduced the timing and brightness of the event, strengthening the magnetar explanation over a rival theory that the blast was powered mainly by interaction with gas shed by the star earlier.
The result gives astronomers a direct probe of what powers superluminous supernovae—nearly 400 have been cataloged in two decades, but their energy source has remained disputed.
A supernova's gamma-ray secret is out. How many more are hiding in existing telescope data?
Are super-magnetic stellar corpses the hidden engines behind the universe’s brightest explosions?
First Gamma-Ray Detection from a Superluminous Supernova: SN 2017egm Confirms Magnetar Engine Model
Overview
Astronomers, including an LSU-led team, used NASA's Fermi Gamma-ray Space Telescope to achieve the first clear detection of gamma rays from the superluminous supernova SN 2017egm. This breakthrough, detailed in a 2026 scientific paper, marks a pivotal moment after nearly two decades of searching Fermi data for such signals. The discovery provides unprecedented insights into the mechanics of superluminous supernovae, revealing that a catastrophic stellar collapse created a supermagnetized neutron star, or magnetar, which powered the explosion. This finding opens new possibilities for understanding the universe's brightest stellar events.