Researchers have identified what they describe as the first confirmed case of two supernova remnants arising from a single binary star system. Analysis centered on the faint remnant G189.6+3.3, which lies adjacent to the well-studied IC 443 remnant, also known as the Jellyfish Nebula, and used long-term gamma-ray measurements to reveal the pair’s connection.
The study combined 16 years of observations from NASA’s Fermi Gamma-ray Space Telescope with X-ray, radio, ultraviolet and optical data to isolate a previously overlooked gamma-ray signal. The results were published July 21 in Nature Communications. Lead author Miltiadis Michailidis, a postdoctoral researcher at Stanford University, said the team initially aimed to characterise the faint remnant rather than to identify a binary origin.
Multiwavelength analysis uncovered a clear compositional split within G189.6+3.3: its northern half is dominated by accelerated protons while the southern half shows electron-driven emission. The proton signature correlates with a dense hydrogen cloud on the northern edge, providing target material for proton collisions that produce gamma rays. Ultraviolet data indicate the northern shock has slowed after colliding with that cloud, supporting the environmental explanation for the differing emission processes.
To assess whether the proximity of the two remnants might be coincidental, the researchers simulated one million hypothetical binary systems and evaluated alignment probabilities. Depending on the modelling approach, the chance of an unrelated close pairing ranged between about 1 in 1,000 and 1 in 100. The team also estimated the explosions occurred tens of thousands of years apart, consistent with sequential detonations in a bound binary pair rather than simultaneous events.
The system offers an empirical testbed for models of massive binary evolution and explosion energetics. By measuring the separation between explosion centres, astronomers can infer supernova energies with fewer theoretical assumptions. The authors plan to search for additional similar pairs across the Milky Way to determine how common such binary remnant systems are. As Miltiadis Michailidis noted, “Now we can actually test it,” referring to energy estimates and evolutionary models enabled by this real-world example.
