Key Takeaways:

  • Scientists for the first time ever witnessed a giant star explode (supernova) in real time.
  • The star, a red supergiant named SN 2020tlf, located 120 million light-years away, showed unusual pre-explosion activity with bright flashes of light as gas erupted from its surface.
  • This surprised scientists as past observations of red supergiants before supernova showed no such violent emissions.
  • The newfound pre-explosion activity provides new insights into the death throes of massive stars.
  • Scientists believe red supergiants undergo major structural changes leading to chaotic gas explosions before collapsing.
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. (Image credit: W. M. Keck Observatory/Adam Makarenko)

For the first time ever, astronomers witnessed a massive star explode in a burning supernova, and the show was even more amazing than the scientists had predicted.

According to a new study published in the Astrophysical Journal, scientists started observing the doomed star more than 100 days before its final, violent collapse. The star is a red supergiant named SN 2020tlf and is located about 120 million light-years from Earth. Big globs of gas burst out of the star’s surface during that lead-up, causing the star to erupt with brilliant flashes of light for the researchers to see.

These pre-supernova pyrotechnics came as a big surprise, as previous observations of red supergiants about to blow their tops showed no traces of violent emissions, the researchers said.

According to a statement from Wynn Jacobson-Galán, the lead study author and research fellow at the University of California, Berkeley, “this is a breakthrough in our understanding of what massive stars do moments before they die.” “For the first time, we watched a red supergiant star explode!”

When big stars go boom

Measuring hundreds or even more than a thousand times the radius of the sun, red supergiants are the largest stars in the universe in terms of volume. (Bulky though they may be, red supergiants are not the brightest nor the most massive stars out there.)

These enormous stars produce energy through the nuclear fusion of elements in their cores, just like our sun does. However, red supergiants can create far heavier elements than the hydrogen and helium that our sun burns because of their immense size. Supergiants’ cores heat up and pressurize more as they burn through ever-larger elements. Eventually, these stars run out of energy, their cores collapse, and they release their gaseous outer atmospheres into space in a violent type II supernova explosion, which occurs when they begin to fuse iron and nickel.

Though they have studied the aftermath of these cosmic explosions and seen red supergiants before they go supernova, scientists have never before witnessed the entire process take place in real time.

The authors of the new study began observing SN 2020tlf in the summer of 2020, when the star flickered with bright flashes of radiation that the team later interpreted as gas exploding off of the star’s surface. The researchers observed the cranky star for 130 days using two telescopes in Hawaii: the W. M. Keck Observatory on Mauna Kea and the University of Hawaii Institute for Astronomy Pan-STARRS1 telescope. Finally, at the end of that period, the star went boom.

At the moment of the explosion, the scientists observed evidence of a dense cloud of gas surrounding the star; they concluded that this gas was probably the same gas that the star had been exhaling in the months before. This suggests that the star started experiencing violent explosions well before its core collapsed in the fall of 2020.

Astrophysicist Raffaella Margutti of UC Berkeley, who co-authored the study, said 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 team concluded that these observations imply that red supergiants experience major structural changes that cause chaotic gas explosions in the final months before collapsing.

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