Supernova explosion caused by stellar collision is seen for the 1st time

Astronomers have found, for the first time, evidence that a black hole or neutron star spiraled its way into the core of a companion star and caused it to explode as a supernova.

Astronomers were informed through data obtained by the Very Large Array Sky Survey (VLASS), a multi-year project using the National Science Foundation’s Karl G. Jansky Very Large Array (VLA).

“Theorists predicted this could happen, but this is the first time we’ve actually seen such an event,” said Dillon Dong, a graduate student at Caltech and lead author of an article reporting the discovery in the journal Science.

The first clue came when scientists examined images from the VLASS, which began observations in 2017, and found an object emitting high-bright radio waves, but which had not appeared in previous research by the VLA.

They determined that the bright radio emission came from the outskirts of a dwarf, star-forming galaxy about 480 million light-years from Earth. They later discovered that an instrument aboard the International Space Station detected an X-ray burst from the object in 2014.

The data from all these observations allowed astronomers to piece together the fascinating story of a centuries-long “dance of death” between two massive stars.

Like most stars that are much more massive than our sun, these two were born as a binary pair, orbiting each other. One was more massive than the other and evolved over its normal lifetime, fueled by nuclear fusion more quickly, and exploded as a supernova, leaving behind a black hole or a superdense neutron star.

“Dance of Death” lasted 300 years

The black hole or neutron star’s orbit got closer and closer to its companion and, about 300 years ago, entered its atmosphere, starting the “dance of death.” At that point, the interaction began to spew gas from the companion into space. The ejected gas, spiraling outward, formed an expanding donut-shaped ring, called a torus, around the pair.

One of the stars was more massive and ended up exploding as a supernova - Reproduction/Bill Saxton, NRAO/AUI/NSF - Reproduction/Bill Saxton, NRAO/AUI/NSF

The ‘dance of death’ among the stars began in the 18th century and lasted for about 300 years

Image: Reproduction/Bill Saxton, NRAO/AUI/NSF

Eventually, the black hole or neutron star made its way into the core of the companion star, interrupting nuclear fusion, producing energy that prevented the core from collapsing by its own gravity.

When the core collapsed, it briefly formed a disk of material orbiting close to the intruder and propelled a jet of material out of the disk at speeds close to that of light, piercing its way through the star.

The collapse of the star’s core caused it to explode as a supernova, following its sister’s earlier explosion.

“All the pieces of this puzzle fit together to tell this incredible story,” said Gregg Hallinan of Caltech. “The remnant of a star that exploded a long time ago plunged into its companion, causing it to explode as well,” he added.