Cosmic supernova witnessed by astronomers as massive star collapses

The moment a dying star collapses into a supernova explosion has been witnessed by astronomers in real time.

In a first for the scientific community, a so-called type II supernova – the ‘death throes’ of a red supergiant star has been recorded.

Researchers at Northwestern University and the University of California, Berkeley observed the red supergiant during its last 130 days leading up to its deadly detonation.

Wynn Jacobson-Galán, the study’s lead author, said in a statement: ‘This is a breakthrough in our understanding of what massive stars do moments before they die.

‘Direct detection of pre-supernova activity in a red supergiant star has never been observed before in an ordinary type II supernova. For the first time, we watched a red supergiant star explode.’

Stars classified as red supergiants have a mass more than 10 times that of our sun. They also have a very cool surface – below 3826°C – and an enormous radii.

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The University of Hawaii Institute for AstronomyPan-STARRS on Haleakalā, Maui, first detected the doomed massive star in the summer of 2020 when a huge amount of light radiating from the red supergiant.

A few months later, in the autumn of 2020, a supernova lit the sky.

The team quickly captured the powerful flash and obtained the very first spectrum of the energetic explosion, named supernova 2020tlf (SN 2020tlf), using the W.M. Keck Observatory’s Low Resolution Imaging Spectrometer on Maunakea in Hawaii.

The researchers have since been studying the data and the resulting study was published this week in the Astrophysical Journal.

Raffaella Margutti, an adjunct associate professor at CIERA and the paper’s senior author, said: ‘It’s like watching a ticking time bomb.

‘We’ve never confirmed such violent activity in a dying red supergiant star where we see it produce such a luminous emission, then collapse and combust, until now.’ 

The team continued to monitor SN 2020tlf after the explosion.

Based on data obtained from Keck Observatory’s Deep Imaging and Multi-Object Spectrograph and Near Infrared Echellette Spectrograph, the researchers determined SN 2020tlf’s progenitor red supergiant star — located in the NGC 5731 galaxy about 120 million light-years away from Earth — was 10 times more massive than the sun.

The data will help illuminate the study of supernovas in the future. Despite their awesome power, they’re a relatively common occurance. Estimates suggest that, somewhere out in the universe, there’s a star exploding every second.

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