The Jellyfish Nebula Has Been Hiding a Body

The Jellyfish Nebula, IC 443, is one of the most studied supernova remnants in the Milky Way. It has been sitting on a secret for roughly 30 years: a second supernova remnant, the corpse of a sibling star, hiding right next to it.

Astrophysicists have long known that most of the galaxy's biggest stars live in multi-star systems, and that most supernovae come from those big stars. Yet no one had ever confirmed two supernovae occurring in a single multi-star system. Until now.

The newly discovered system pairs IC 443 with a second, fainter remnant called G189.6+3.3, lurking nearby. IC 443 shines so brightly that it had been masking this second remnant, which only became detectable via old data and fresh observations from newer, more sensitive space telescopes.

A satellite first spotted the second shell in an X-ray survey in 1994, and astronomers placed it on a candidate list. It sat there for close to three decades. Nobody could find the radio shell they typically require before calling something a confirmed supernova remnant. What finally cracked it open was 16 years of observations from the Fermi Large Area Telescope.

The Jellyfish Nebula is estimated to be 8,000 to 9,000 years old; its companion may be between 20,000 and 110,000 years old, suggesting the two explosions were separated by as much as 100,000 years. Two stars. One system. They died alone, millennia apart, and left behind a puzzle that took three decades of accumulated photons to begin solving.

The question of how many of the roughly 300 catalogued galactic remnants have a hidden sibling, masked by the same mechanism, is now an answerable one. That is not a comfortable place to leave the inventory.

Read the full story at Scientific American, July 21, 2026

Hot Take: The second remnant spent 30 years on an astronomical "candidate list," the cosmic equivalent of a sticky note nobody acted on. It was, in the interim, the first confirmed binary supernova pair in galactic history.