BURSTFor the first time, scientists may have discovered a binary system—like the twin suns of the fictional planet Tatooine in "Star Wars"—where both stars exploded as supernovas, a new study finds.
Although Earth may orbit around a single star, more than half of all stars are in systems where two or more suns orbit each other. "When it comes to massive stars, the percentage in multiple systems are even higher," study lead author Miltiadis Michailidis, a postdoctoral fellow at Stanford University in California, told Space.com.
When massive stars burn all their fuel, they can die in giant explosions known as supernovas. These outbursts can briefly outshine all of the other suns in these stars' galaxies. They often leave behind expanding super-hot clouds of debris known as supernova remnants. Astronomers have detected about 300 such remnants in our galaxy to date.
Given how often massive stars are found in binary systems, "one can expect many pairs of massive stars where both will explode as supernovas," Michailidis noted. "However, this has never been observed, until now."
One reason supernova pairs may have escaped attention is that "if the stars are too close together when they exploded, the resulting supernova remnants may look like that from a single explosion," Michailidis explained. Another is that one star going supernova may propel its partner far enough away to hide the fact they were ever a duo, he added.
In the new study, Michailidis and his colleagues investigated a supernova remnant known as IC 443, located about 6,000 light-years from Earth in the constellation Gemini. IC 443 is also known as the Jellyfish Nebula for how it resembles a jellyfish.
IC 443 is one of the most extensively studied supernova remnants in the galaxy because of how shock waves from the supernova have collided with surrounding clouds of gas and dust to create a set of concentric bubble shells, "much like how a drop of water falling on a lake creates circular waves," Michailidis said. "It is very isolated from its surroundings, without many other objects nearby to complicate its very bright emissions."
The scientists analyzed one of IC 443's much dimmer, long-hidden neighbors, dubbed G189.6+3.3. The German-led ROSAT (Roentgen Satellite) mission first discovered G189.6+3.3 in 1994 via its faint X-ray emissions, and the Russian-German Spektrum Roentgen Gamma (SRG) space observatory later clearly detected shell-like structures within G189.6+3.3, suggesting that it was a supernova remnant.
In the new study, the researchers analyzed more than 16 years of data from NASA's Fermi Gamma-ray Space Telescope along with earlier X-ray, optical and radio measurements. They discovered signs that both IC 443 and G189.6+3.3 were both smashing into the same interstellar cloud of hydrogen, revealing they were close together in space, with the centers of their explosions about 30 to 50 light-years apart.
The researchers calculated that the chances of randomly encountering two unrelated supernova remnants at this distance from one another "was about one in 1,000," Michailidis said. "This suggests that our discovery is in fact the first known binary-system supernova pair."
The scientists estimated that G189.6+3.3 was older than IC 443, with the parent star of G189.6+3.3 exploding between 20,000 to 110,000 years ago, while IC 443 was created about 8,000 to 9,000 years ago. The original stars may have been 20 or more times the sun's mass.
These new findings can help shed light on how massive binary stars evolve, interact and die. For instance, further analysis of G189.6+3.3 and IC 443 can reveal how much of a kick the former gave the latter when it died, Michailidis said.
The scientists detailed their findings July 21 in the journal Nature Communications.