NASA's Fermi Mission Discovers Possible Binary Supernova System

A new study using 16 years of data from NASA's Fermi Gamma-ray Space Telescope has uncovered evidence of a remarkable cosmic pairing: two supernova remnants that likely originated from stellar siblings that once orbited each other. The research, led by Miltiadis Michailidis, a postdoctoral fellow at Stanford University, identifies a faint supernova remnant called G189.6+3.3, which had previously been hidden in the gamma-ray glare of its brighter neighbor, the Jellyfish Nebula (IC 443). Both remnants are located in the constellation Gemini and show striking spatial and physical connections, suggesting they represent the first known example of a binary system where both stars have undergone supernova explosions.

The two star remnants appear to partially overlap as seen in X-rays, with recent observations indicating that hot plasma associated with G189.6+3.3 likely extends across the entire region. A bright filament of gas between the overlapping remnants provides key evidence of their interaction: the shock wave from G189.6+3.3 slammed into dense interstellar gas and dramatically slowed, indicating both remnants are interacting with the same cloud system. The scenario proposed by researchers suggests that the first star's explosion sent its binary companion hurtling through space, and after traveling for thousands of years, the surviving star eventually detonated as well.

The analysis focused on detecting gamma rays produced through a specific high-energy mechanism. When cosmic-ray protons accelerated by supernova shock waves collide with interstellar gas, they produce neutral pions that decay into pairs of gamma rays. This emission occurs within a specific energy band that Fermi's Large Area Telescope (LAT) is equipped to detect. The Jellyfish Nebula was confirmed in 2013 to produce gamma rays through this mechanism, while its companion G189.6+3.3 was first discovered in 1994 during an X-ray survey by the German-led ROSAT mission.

Astronomers now suspect the Jellyfish Nebula may be a candidate PeVatron—a cosmic particle accelerator capable of boosting protons to exceptionally high energies that could allow them to nearly escape the galaxy. Finding a second particle accelerator near the Jellyfish Nebula provides new opportunities for understanding how supernova remnants function as cosmic accelerators. Michailidis presented these findings on June 18, 2026, at the 248th meeting of the American Astronomical Society in Pasadena, California. A detailed paper describing the results will be published in Nature Communications.