For the first time, a team of astronomers have captured solid evidence for a rare double cosmic cannibalism : a star swallowing a compact object like a black hole or neutron star. In turn, that object engulfed the core of the star, causing it to explode and leave only a black hole.
Evidence for this rare phenomenon was detected using data collected by the Very Large Array Sky Survey (VLASS), a radio telescope consisting of 27 huge antennas in the New Mexico desert near Socorro County. They observed that a compact object spiraled its way into the core of a companion star in the VT 1210 + 4956 system and caused it to explode as a supernova. The Keck telescope also captured a light burst of material spewing in all directions at 3.2 million kilometers per hour from a central location, suggesting that an energy explosion had taken place there in the past.
“We thought, ‘Wow, this is interesting,'” said Dillon Dong, a Caltech astronomer and leader of the work that publishes the journal Science.
This meltdown-caused core collapse supernova had been theorized before, but astronomers had never found evidence for one. Up to now.
“Massive stars generally explode as supernovae when they run out of nuclear fuel,” said Gregg Hallinan, a professor of astronomy at Caltech and a co-author of the study. “But in this case, an invading black hole or neutron star has prematurely caused its companion star to explode.” This is the first time that a supernova caused by a merger has been confirmed.
Data from various observations dating back to 2017 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, closely orbiting each other. One of them was more massive than the other and evolved throughout its life driven by faster nuclear fusion , exploding as a supernova, leaving behind a black hole or a super dense neutron star.
“The companion star was going to explode eventually, but this merger sped up the process, ” Dong said.
The material ejected by the initial supernova explosion moved much faster than the material previously thrown by the companion star, and when VLASS observed the object, the supernova explosion was colliding with that material, causing powerful collisions that produced the bright radio broadcast seen by the VLA.
“All the pieces of this puzzle fit together to tell this incredible story,” clarified Hallinan, “The remnant of a star that exploded long ago sank into its companion, causing it to explode as well.”
The VLA Sky Survey produces an incredible amount of data, so discoveries like this are truly like finding a needle in a haystack. Now that astronomers know how to look for these multiple lines of evidence, they are expected to find more examples of this strange cosmic phenomenon.
Referencia: D. Dong et al. A transient radio source consistent with a merger-triggered core collapse supernova. Science. Vol. 373, September 3, 2021, p. 1125. doi: 10.1126/science.abg6037.
