For the first time that scientists have witnessed the closing days and death throes of a red supergiant star before it explodes into a supernova.
In most cases, supernovae are discovered after they have already occurred. However, a handful of different types have been observed as they were about to go off. Then, about 130 days before it exploded, astronomers could see the star’s last stages, including its gradual brightening and eventual explosion.
A senior author of an investigation on the supernova in the Astrophysical Journal, Raffaella Margutti, described it as “watching a ticking time bomb.” It’s the first time a dying red supergiant star has been observed to create such a bright emission before collapsing and combusting.
A galaxy 120 million light-years away contained the star, but neither the star nor its galaxy can be seen with the human eye.
The Pan-STARRS telescope indicated that the star was furiously ejecting massive volumes of gas, so the astronomers continued to monitor it.
They were fortunate enough to record the intense flash of light it released—brighter than all the other stars in the galaxy put together at the same time.
Margutti, currently an associate professor at the University of California, Berkeley, conducted the research while working as a postdoctoral fellow in Evanston, Illinois.
New research led by Margutti’s graduate student, astrophysicist Wynn Jacobson-Galán, has been published in the journal Science.
The University of Hawaii’s Pan-STARRS observatory on Maui’s Haleakala volcano identified the star in the summer of 2020, according to Jacobson-Galán.
It was clear from the supernova flash and observations that followed that the star was engulfed in gas at the time of the explosion. This gas was most likely the same as what it had been ejecting for the month prior.
A few previous supernovas have been observed, but none of this sort. Jacobson-Galán said that these collisions have often occurred when a massive star has collided with its binary companion.
However, no other stars seemed to be involved in this explosion.
Jacobson said, “these types of supernovae come from a massive star, and it’s usually a red supergiant, and that’s what we saw, they are one of the more common supernovae in the universe.”
This supernova was found to be at the lower end of the size range for stars to explode into supernovas, based on observations made after the event.
Our sun is too tiny to explode into a supernova. After its life, it will become a white dwarf.
In addition, smaller stars, according to Jacobson, can endure for billions of years since their fusion fuel isn’t depleted as quickly.
Unlike the explosion in this study, red giants such as the supernova can only consume fuel for a few hundred million years before collapsing.
The last explosion results from the star’s outer shells “bouncing” off its core, which is the trigger; as it spreads outward, it releases the star’s bonds, rips apart the star, and rapidly expels all of its layers.
Many stars die in a supernova explosion, which releases “heavy” chemical elements into surrounding interstellar clouds of gas and dust.
To create new stars and planets from debris left behind in the wake of exploding clouds is a process known as cloud seeding.
According to University of Birmingham professor Matt Nicholl, astronomers have examined huge stars’ “old age” for the first time in decades, a previously inaccessible era.
Nicholl wasn’t involved in the current study, but he headed a team that identified the brightest supernova yet observed.
Albert Zijlstra, a professor of astrophysics at the University of Manchester in the United Kingdom, stated in an email that the brightening of the star before it became a supernova may have been unconnected.
It shines brighter than the surrounding stars for many years but eventually fades away without exploding. A comparable star, Eta Carinae, is nearly 7,500 light-years distant and emits massive gas clouds.
“They’ve seen a brightening before the explosion, but there’s no way to know that the star didn’t do the same thing 10 years ago, so we don’t know whether the two things are related.”