Most of the largest stars in the universe do not exist alone. Instead, they are born alongside a partner star in what scientists call a binary system, spending their entire lives locked together by gravity. But as with all things, that bond eventually comes to an end.
For the first time ever, scientists have uncovered evidence of two enormous stars from one of these paired systems that both exhausted their fuel and exploded in violent blasts, each leaving behind a glowing cloud of gas known as a nebula. These stellar explosions are referred to as supernovas.
One of the two nebulas involved is among the most recognizable in our Milky Way galaxy — the Jellyfish Nebula, named for its resemblance to the ocean creature.
Using more than 16 years of data collected by NASA’s Fermi Gamma-ray Space Telescope, researchers identified a second nebula located relatively close to the Jellyfish Nebula. That second discovery has helped scientists understand the Jellyfish Nebula as part of a much larger cosmic double catastrophe.
Scientists believe the Jellyfish Nebula — formally known as IC 443 — was created when a star roughly 15 to 25 times the mass of our sun reached the end of its life and exploded. The second nebula, formally designated G189.6+3.3, is thought to have been produced by the explosion of that star’s binary companion, which was at least 20 times more massive than the sun.
While alive, both stars are believed to have been tens of thousands of times brighter than our sun. After the explosions, both may have collapsed into incredibly dense objects known as neutron stars.
Both nebulas sit roughly 6,000 light-years from Earth in the constellation Gemini. To put that in perspective, one light-year equals the distance light covers in a single year — approximately 5.9 trillion miles, or 9.5 trillion kilometers.
The discovery could shed new light on how massive binary star systems form, live, and die.
“This system provides a rare opportunity to reconstruct the complete evolutionary history of a massive binary — from the birth and interaction of two massive stars, through both supernova explosions, to the remnants they left behind,” said Miltiadis Michailidis, a postdoctoral fellow in Stanford University’s physics department and lead author of the study published Tuesday in the journal Nature Communications.
Michailidis noted that while most massive stars are born in binary systems, no such pair in which both stars exploded as supernovas and left behind detectable remnants had ever previously been identified.
It is worth noting that some massive stars are born into systems with three or more stars. The two nebulas themselves are expanding structures made up of hot gas, accelerated particles, and interstellar material disturbed by the original explosions.
Massive stars tend to live fast and die young — burning brilliantly for only a few million years, compared to the roughly 10 billion years our sun is expected to last.
“Systems like this one can provide direct observational constraints on how the evolution of massive stars is modified by the presence of a binary companion — one of the major outstanding questions in stellar astrophysics,” Michailidis said. “Until now, our understanding of these final evolutionary stages has relied almost entirely on theoretical models and numerical simulations.”
According to the researchers, the star connected to the newly identified nebula was the first of the two to explode, and that blast sent its companion spinning off course. Scientists estimate that somewhere between 20,000 and 110,000 years passed between the two explosions.
“The first explosion disrupted the binary, and the surviving companion continued moving through space until it also exploded,” Michailidis said.
The two stars once orbited each other at an extremely close distance — possibly just a few times the distance between Earth and the sun. However, the centers of the two supernova remnants are now separated by 30 to 50 light-years.
While the binary system was still intact, the stars were close enough that material may have flowed from one star to the other in a process called mass transfer.
Michailidis said it remains unclear whether the first explosion directly set off the second. “By the time the first supernova occurred, the second star may already have been close to the end of its life,” he said.
