NASA's Fermi Spies a Supercharged Supernova

Released Wednesday, May 20, 2026

ID: 15041

- Visualizations by:
- Jonathan North

Gamma rays detected by NASA’s Fermi Gamma-ray Space Telescope gave scientists a look under the hood of a rare supernova that produced much more light than normal.

Credit: NASA’s Goddard Space Flight Center

Music credits:

"Granular Game" by John Bisset

"In The Zone" by Daniel Migdal, Jonas Pomo

"Ornaments" by Lisa Van Hal

An analysis of data from NASA’s Fermi Gamma-ray Space Telescope concludes the mission detected a rare, unusually luminous supernova that, researchers say, likely received its power-up from a magnetar born in the stellar collapse that triggered the explosion.

Astronomers have searched Fermi data for gamma-ray signals from thousands of supernovae, but none were definitive until now.

Core-collapse supernovae occur when the energy-producing center of a star many times our Sun’s mass runs out of fuel, collapses under its own weight, and explodes. During the collapse, a city-sized neutron star or an even smaller black hole may form. A blast wave blows away the rest of the star, which rapidly expands as a hot, dense cloud of ionized gas.

In the last couple of decades, astronomers have identified nearly 400 exceptional core-collapse supernovae. Each of these events, dubbed superluminous supernovae, produced 10 or more times the amount of visible light normally seen.

In 2024, a study noted that Fermi’s Large Area Telescope may have seen gamma rays from a superluminous supernova called SN 2017egm.

The supercharged outburst occurred in galaxy NGC 3191, located about 440 million light-years away in the constellation Ursa Major. Even at this distance, the explosion remains one of the closest of its type to us on Earth. The new research confirms that Fermi saw the explosion, opening a new window for studying these events.

What makes these explosions brighter than normal supernovae? Theorists think it’s the formation of a magnetar, a type of neutron star with the strongest magnetic fields known — up to 1,000 times the intensity of typical neutron stars. That’s 10 trillion times stronger than a refrigerator magnet.

Scientists expect a newly formed magnetar to spin a few hundred times a second. This rapid rotation produces a strong outflow of electrons and positrons, their antimatter counterparts, that forms a vast cloud of energetic particles.

Within this cloud — called a magnetar wind nebula — various interactions fuel the production and absorption of gamma rays, the most energetic form of light. Unable to escape directly, the gamma rays become reprocessed, downshifted into lower-energy visible light that provides the supernova with its extra boost of light.

The study shows that a magnetar model best reproduces both the supernova’s luminosity and the arrival time of its gamma rays during the first months, but after that time, additional processes may be needed to account for the supernova’s irregularly fading visible light.

This composite image shows two views of SN 2017egm, in visible light (inset) and gamma rays (background). The optical image shows the supernova — the brightest object in the scene — and its host galaxy on July 1, 2017. The background map shows a wide area of the sky surrounding the supernova’s position. Brighter colors indicate greater statistical likelihood that gamma rays are associated with the explosion. The map includes gamma rays detected by Fermi’s Large Area Telescope from July 5, 2017, to Oct. 25, 2017, or from 43 to 155 days after the supernova was discovered.

Credit: Background, NASA/DOE/Fermi LAT Collaboration and Acero et. al. 2026; inset, NOT+ALFSOC/Bose et al. 2020

Alt text: Composite showing optical and gamma-ray observations of SN 2017egm

Image description: On a deep blue background, irregular blobs pepper the image in lighter shades of blue, and at the top and right side, some red as well. The largest blob, just below center, has a yellow core rimmed first in red and then in blue. A label reads “SN 2017egm.” A faint yellow wedge with its apex centered on this blob extends toward the upper left. It encloses a photograph speckled with digital noise that shows a face-on spiral galaxy in yellows and grays bearing a large, circular, whitish source left of its center. There are scale bars in both images. The background bar has text reading “30 arcminutes” — about the apparent size of a full moon — and the inset’s bar has text reading “10 arcseconds,” representing a size 180 times smaller than the background’s bar.

The superluminous supernova SN 2017egm was discovered by the European Space Agency’s Gaia mission on May 23, 2017. It exploded in a massive barred spiral galaxy known as NGC 3191, shown on the left before the eruption. The image at right, taken on July 1, 2017, shows the supernova outshining the entire galaxy.

Credit: Left, SDSS and PS1; right, NOT+ALFSOC/Bose et al. 2020

Alt text: NGC 3191 before and after SN 2017egm

Image description: Two pictures of a galaxy appear side by side, with the image at right speckled with digital noise and shown in yellows and grays instead of the more vibrant blues of the left photo. In the right image, a bright source — essentially a large white circle — has appeared to the left of the galaxy’s yellowish core, outshining the whole galaxy.

A massive barred spiral galaxy known as NGC 3191 was host to superluminous supernova SN 2017egm, seen here before the explosion.

Credit: SDSS and PS1

Alt text: NGC 3191 before SN 2017egm

Image description: A face-on spiral galaxy with an off-white central core and thick blue-gray arcing arms appears against the blackness of space.

The massive barred spiral galaxy known as NGC 3191 as seen on July 1, 2017, during the eruption of superluminous supernova SN 2017egm. The explosion was discovered by ESA's (European Space Agency's) Gaia mission on May 23, 2017.

Credit: NOT+ALFSOC/Bose et al. 2020

Alt text: NGC 3191 after SN 2017egm

Image description: An image of a face-on galaxy shown in yellows and grays is speckled with digital noise, which gives the background a mottled look. A bright source essentially a large white circle tinged with blue appears to the left of the galaxy’s yellowish core, outshining the whole galaxy.

The Crab Nebula formed in a supernova explosion observed in 1054. At its heart lies an isolated neutron star, the crushed core of the original star. It spins about 30 times a second, sweeping a beam of radiation toward Earth with every rotation, lighthouse style, which classifies the neutron star as a pulsar. This rapid spin powers X-ray jets (elongated blue-white feature near center) and a high-speed outflow of electrons and other particles. The particles collect in a vast cloud-like structure called a pulsar wind nebula, which also forms around magnetars, the pulsar’s supermagnetized cousin. This emission gradually slows the neutron star’s spin. These images combine X-ray data from NASA’s Chandra X-ray Observatory (bluish white) and infrared data from NASA’s James Webb Space Telescope.

Credit: X-ray, Chandra: NASA/CXC/SAO; Infrared, Webb: NASA/STScI; Image Processing: NASA/CXC/SAO/J. Major

Alt text: X-ray and infrared composite of the Crab Nebula

Image description: Against a starry background lies a colorful, roughly elliptical cloud taking up most of the frame. Its outer edges are formed by gray, red, and yellow loops and tendrils, parts of which seem to be outward-moving splashes and rivulets of color. The inner area is filled with a faint bluish glow that brightens toward the center. Brighter bluish-white rings make up a kind of bull’s-eye surrounding the pulsar, and an elongated structure curves diagonally downward.

The X-ray glow associated with a source known as Swift J1834.9-0846, located near the center of the W41 supernova remnant, comes from the first magnetar wind nebula identified (outline).

Credit: ESA/XMM-Newton and Younes et al. 2016

Alt text: X-ray image of first known magnetar wind nebula

Image description: Pixelated blobs in various sizes and colors emerge from a black background. At the center, a yellow outline encloses a large blob predominantly in green and blue-white. A thin white line extends from the brightest spot to a label at about 10 o’clock that reads “Magnetar.” A white scale bar at lower left indicates a width of 10 light-years, with corresponding text.