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Scientists watch enormous star violently explode after ominous goodbye

Deep in space, a red supergiant dramatically blows up.

Monisha Ravisetti Former Science Writer
Monisha Ravisetti was a science writer at CNET. She covered climate change, space rockets, mathematical puzzles, dinosaur bones, black holes, supernovas, and sometimes, the drama of philosophical thought experiments. Previously, she was a science reporter with a startup publication called The Academic Times, and before that, was an immunology researcher at Weill Cornell Medical Center in New York. She graduated from New York University in 2018 with a B.A. in philosophy, physics and chemistry. When she's not at her desk, she's trying (and failing) to raise her online chess rating. Her favorite movies are Dunkirk and Marcel the Shell with Shoes On.
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Monisha Ravisetti
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An artist's representation of a red supergiant exploding.

 W.M. Keck Observatory/Adam Makarenko

For years, experts thought the biggest stars in the universe, red supergiants, died with a whimper. But in 2020, astronomers witnessed quite the opposite. One of these gleaming monsters -- 10 times more massive than the sun -- violently self-destructed after presenting the cosmos with a final, radiant beacon of starlight.

"This is a breakthrough in our understanding of what massive stars do moments before they die," Wynn Jacobson-Galán said in a statement Thursday. Jacobson-Galán is an astronomy research fellow at the University of California, Berkeley, and formerly was a graduate student researcher at Northwestern University, where a study of the dying star was conducted. "For the first time, we watched a red supergiant star explode."

Jacobson-Galán is the lead author of a paper published Thursday in The Astrophysical Journal that documents the star's eruption as well as its last, 130-day hurrah. 

During the research team's careful watch, members noticed the stellar leviathan, located about 120 million light-years from Earth in the NGC 5731 galaxy, glistening before its death, offering a sparkly yet ominous goodbye to the land of the living. 

"It's like watching a ticking time bomb," Raffaella Margutti, of Northwestern's Center for Interdisciplinary Exploration and Research in Astrophysics, and the paper's senior author, said in a statement. 

The star's extreme illumination indicated it wasn't dormant, or quiescent, as previously observed red supergiants had been prior to their demise. This shiny orb was very much active as it deteriorated, presumably releasing pent-up gas with great vigor and altering its internal structure somehow, according to the team.

Then, once the "bomb" detonated, a climactic Type II supernova event labeled SN2020tlf flooded the sky with light. "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," Margutti said. "Until now."

The researchers made the revelatory find by remotelycollecting data from Hawaii's Keck Observatory Deep Imaging and Multi-Object Spectrograph as well as Near Infrared Echellette Spectrograph. This innovative way of remotely retrieving astrophysical information fuels discoveries in a timely manner. 

In the future, the group hopes to continue using the remote method to document even-more-surprising transient happenings, including events involving other enormous supernovas like the one chronicled in their recent study. "I am most excited by all of the new 'unknowns' that have been unlocked by this discovery," Jacobson-Galán said. 

"Detecting more events like SN2020tlf," Jacobson-Galán added, "will dramatically impact how we define the final months of stellar evolution, uniting observers and theorists in the quest to solve the mystery on how massive stars spend the final moments of their lives."