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Astronomie - Supernova early-warning system developed to pinpoint the moment massive stars will explode

21.10.2022

A star's death is explosive, mystifying and out of this world – and now, scientists have figured out a way to watch it happen in real-time. Astronomers developed an "early-warning system" to alert scientists when a star is on the verge of dying in a supernova explosion. 

Until now, it's been difficult for scientists to observe the moment a star explodes. But for the first time, researchers have simulated that sudden journey to a star's demise. Researchers found that in a star's "red supergiant" phase – the last phase of its life – dense material accumulates around it and the star becomes drastically dimmer.

"The dense material almost completely obscures the star, making it 100 times fainter in the visible part of the spectrum," Ben Davies, lead author of the study, said in a press release. "This means that, the day before the star explodes, you likely wouldn't be able to see it was there." 

Prior to the new research, which was published in Monthly Notices of the Royal Astronomical Societyon Thursday, astronomers were unsure how long it took that sort-of "cocoon" of dense material to gather. Most late-life images of stars are from about a year before they explode, Liverpool John Moores University's Astrophysics Research Institute said in a press release. But in those images, the stars aren't surrounded by material; they just look normal. 

That means that it takes less than a year for that shell of debris to gather and the supernova to occur. They also found that "red supergiants" undergo a "mass-losing event" shortly before they explode, a situation that "radically alters" their appearance. 

Basically, scientists found, the tell-tale sign of a supernova is that the star will "dramatically change."

"Until now, we've only been able to get detailed observations of supernovae hours after they've already happened," Davies said. "With this early-warning system we can get ready to observe it in real-time, to point the world's best telescopes at it, and watch the surface of the star getting literally ripped apart in front of our eyes."

Quelle: CBS News

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Red Alert: massive stars sound warning they are about to go supernova

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This artist’s impression shows the supergiant star Betelgeuse as it was revealed thanks to different state-of-the-art techniques on ESO’s Very Large Telescope (VLT), which allowed two independent teams of astronomers to obtain the sharpest ever views of the supergiant star Betelgeuse. They show that the star has a vast plume of gas almost as large as our Solar System and a gigantic bubble boiling on its surface. These discoveries provide important clues to help explain how these mammoths shed material at such a tremendous rate.
Credit
European Southern Observatory/L. Calçada

Astronomers from Liverpool John Moores University and the University of Montpellier have devised an ‘early warning’ system to sound the alert when a massive star is about to end its life in a supernova explosion. The work was published in Monthly Notices of the Royal Astronomical Society.

In this new study, researchers determined that massive stars (typically between 8 and 20 solar masses) in the last phase of their lives, the so-called ‘red supergiant’ phase, will suddenly become around a hundred times fainter in visible light in the last few months before they die. This dimming is caused by a sudden accumulation of material around the star, which obscures its light.

Until now, it was not known how long it took the star to accrete this material. Now, for the first time, researchers have simulated how red supergiants might look when they are embedded within these pre-explosion 'cocoons'. 

Old telescope archives show that images do exist of stars that went on to explode around a year after the image was taken. The stars appear as normal in these images, meaning they cannot yet have built up the theoretical circumstellar cocoon. This suggests that the cocoon is assembled in less than a year, which is considered to be extremely fast.

Benjamin Davies from Liverpool John Moores University, and lead author of the paper, says “The dense material almost completely obscures the star, making it 100 times fainter in the visible part of the spectrum. This means that, the day before the star explodes, you likely wouldn't be able to see it was there.” He adds, “Until now, we’ve only been able to get detailed observations of supernovae hours after they’ve already happened. With this early-warning system we can get ready to observe them real-time, to point the world’s best telescopes at the precursor stars, and watch them getting literally ripped apart in front of our eyes.”

Quelle: Royal Astronomical Society

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