Ground-based telescopes delivered the first real-time view of a red supergiant star's death throes. While they are neither the brightest nor most massive stars, they are the biggest in terms of volume.
| An artist’s rendition of a red supergiant star transitioning into a Type II supernova |
Betelgeuse is a well-known red supergiant star that has gained popularity owing to its erratic fading. While it was projected that Betelgeuse would explode as a supernova, it has remained stable.
However, the star at the core of this new study, which is situated roughly 120 million light-years from Earth in the NGC 5731 galaxy, had ten times the mass of the sun when it exploded.
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. Credit: W. M. Keck Observatory/Adam Makarenko
Some stars have explosive eruptions or emit blazing hot layers of gas just before they die in a blaze of glory. Until this incident, astronomers assumed that red supergiants were generally quiet before bursting into supernovae or collapsing into dense neutron stars.
Instead of that, astronomers saw the star self-destruct violently before dying in a type II supernova. This kind of star death occurs when a huge star collapses and explodes violently after burning through the hydrogen, helium, and other components in its core.
All that is left is the star's iron, and as iron cannot fuse, the star will eventually run out of energy. When this occurs, the iron collapses, resulting in the explosion. The Astrophysical Journal released a report describing these results.
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| PS1/YSE g-band explosion image of Type II SN 2020tlf in host galaxy NGC 5731. |
"This is a breakthrough in our understanding of what massive stars do moments before they die," said lead study author Wynn Jacobson-Galán, a National Science Foundation Graduate Research Fellow at University of California, Berkeley, in a statement.
"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."
Astronomers initially became aware of the star's odd behavior 130 days before it exploded as a supernova. The University of Hawaii Institute for Astronomy's Pan-STARRS telescope on Maui's Haleakala observed bright radiation in the summer of 2020.
The researchers then watched a supernova in the same location in the fall of that year.
They discovered it on Maunakea, Hawaii, using the W.M. Keck Observatory's Low-Resolution Imaging Spectrometer and dubbed it supernova 2020tlf. Their studies indicated that material was present around the star at the time of the explosion — the bright gas that the star forcefully flung out during the summer.
"It's like watching a ticking time bomb," said senior study author Raffaella Margutti, an associate professor of astronomy and astrophysics at UC Berkeley, in a statement. "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 discovery indicates that some of these huge stars undergo significant internal alterations that result in the chaotic discharge of gas just before they die.
Reference(s): Peer-Reviewed Research Paper
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April 25, 2022
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