An artist's rendition of a red supergiant star transitioning into a Type II supernova, emitting a violent eruption of radiation and gas on its dying breath before collapsing and exploding. (Image credit: W. M. Keck Observatory/Adam Makarenko)
For the first time, astronomers have witnessed a massive star explode in a flaming supernova — and the show was even more spectacular than the experts had predicted.
According to a research published in the Astrophysical Journal, scientists began observing the doomed star — a red supergiant called SN 2020tlf and located approximately 120 million light-years from Earth — more than 100 days before its last, cataclysmic collapse. The researchers observed the star erupt with dazzling bursts of light as large globs of gas exploded off of the star's surface during that time.
The researchers noted that earlier observations of red supergiants preparing to blow their tops showed no indications of strong emissions, thus these pre-supernova fireworks came as a great surprise.
In a statement, lead study author Wynn Jacobson-Galán, a research scholar at the University of California, Berkeley, said, "This is a milestone in our understanding of what huge stars do moments before they die." "We saw a red supergiant star burst for the first time!"
When big stars go boom
In terms of volume, red supergiants are the biggest stars in the cosmos, measuring hundreds or even thousands of times the radius of the sun. (Despite their bulk, red supergiants are neither the brightest nor the most massive stars in the sky.)
These huge stars, like our sun, create energy by nuclear fusion in their cores. Red supergiants, on the other hand, may generate considerably heavier elements than the hydrogen and helium that our sun burns because they are so massive. Supergiants' cores become hotter and more pressured as they burn more enormous components. These stars eventually run out of energy when they start fusing iron and nickel, their cores collapse, and their gaseous outer atmospheres are ejected into space in a violent type II supernova explosion.
Scientists have spotted red supergiants before they go supernova and analysed the aftermath of these cosmic explosions, but they've never watched the entire process in real time before.
In the summer of 2020, the authors of the new study began studying SN 2020tlf, when the star flashed with dazzling bursts of radiation that the scientists later interpreted as gas erupting from the star's surface. The researchers tracked the irritable star for 130 days using two telescopes in Hawaii: the University of Hawaii Institute for Astronomy Pan-STARRS1 telescope and the W. M. Keck Observatory on Mauna Kea. The star finally went boom at the end of that time span.
The researchers noticed a dense cloud of gas encircling the star at the moment of its explosion, which they believe was the same gas that the star had ejected in the months before. This shows that intense explosions began long before the star's core disintegrated in the fall of 2020.
"Until now, we've never seen such dramatic activity in a dying red supergiant star, where we witness it emit such a brilliant emission, then collapse and burn," study co-author and UC Berkeley astrophysicist Raffaella Margutti said in a release.
These findings show that red supergiants endure major internal structural changes, resulting in chaotic gas bursts in their final months before collapsing, according to the scientists.
Reference: Astrophysical Journal
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