Despite the massive number of stars in the sky, spotting one in the throes of a supernova is still an incredibly rare event. Now astronomers have capture a red supergiant before, during and after a supernova explosion for the first time, bringing together crucial new information on these dramatic events.
“It’s a breakthrough in our understanding of what massive stars do moments before they die,” said lead author Wynn Jacobson-Galán (UC Berkeley). “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 saw a red supergiant star explode! “
Using the Pan-STAR telescope in Maui, Hawai’i, scientists detected the doomed red supergiant star in the summer of 2020 thanks to the enormous amount of light it emitted. Later in the fall, when it became a supernova, the team captured the powerful flash using the Hawai’i-based system. Keck ObservatoryLow resolution imaging spectrometer (LRIS). They also captured the very first spectrum of the supernova, known as SN 2020tlf.
Observations showed that the star likely ejected massive amounts of dense circumstellar material just before the explosion. Previous observations have shown that red giants were relatively calm before becoming supernovas, so new data suggests that some may significantly change their internal structure before exploding. This could then result in tumultuous gas ejections moments before the collapse.
SN 2020tlf is located in the galaxy NGC 5731 about 120 million light years from Earth and was about 10 times more massive than the Sun. Stars become supernovae when they run out of fuel and collapse by their own gravity, fueling a massive carbon fusion explosion. For this to happen, they must be large enough (8 to 15 solar masses) or they will simply collapse into a white dwarf star like our Sun will eventually. Bigger than that and they might collapse into a black hole.
The discovery will now allow scientists to study red supergiant stars for similar types of light radiation that could signal another supernova. “Detecting more events like SN 2020tlf will have a huge impact on how we define the final months of stellar evolution …
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