Astronomers have long suspected that most massive and luminous stars explode when they die, and now they have the proof to back it up.
In a study released this week, experts detailed how they were able to confirm that one star belonging to the Wolf-Rayet category died in a massive explosion called a Type IIB supernova, according to a Berkeley Lab press release.
They were able to observe the supernova, named SN 2013cu, by using space- and ground-based telescopes.
"Newly developed observational capabilities now enable us to study exploding stars in ways we could only dream of before. We are moving towards real-time studies of supernovae," said Gal-Yam of the Weizmann Institute of Science in Rehovot, Israel, and the study's lead author, in a statement according to the release.
Wolf-Rayet stars are over 20 times larger and almost five times hotter than the sun, which is 330,000 times bigger than Earth and has a surface temperature of 18,000 degrees Fahrenheit, according to the release.
For the study, scientists used resources available at the National Energy Research Scientific Computing Center and the Energy Sciences Network, both of which are located at the U.S. Department of Energy's Lawrence Berkeley National Laboratory, or Berkeley Lab, in California.
"When I identified the first example of a Type IIb supernova in 1987, I dreamed that someday we would have direct evidence of what kind of star exploded. It's refreshing that we can now say that Wolf-Rayet stars are responsible, at least in some cases," says Alex Filippenko, Professor of Astronomy at UC Berkeley, according to the release.
The researchers were able to confirm that some giant stars become Wolf-Rayets in the final stages of their lives and they "enrich" galaxies with the heavy chemical elements that become the building blocks for life and planets.
"We are gradually determining which kinds of stars explode, and why, and what kinds of elements they produce," says Filippenko. "These elements are crucial to the existence of life. In a very real sense, we are figuring out our own stellar origins."
The researchers also confirmed the large stars reach the Wolf-Rayet phase before the explosion. When nuclear fusion slows, the heavy elements in the star's center rise to the surface, which sets off powerful winds. This sheds a great deal of material into space, according to the release.
"When a Wolf-Rayet star goes supernova, the explosion typically overtakes the stellar wind and all information about the progenitor star is gone," said Peter Nugent of the Berkeley Lab, according to the release. "We got lucky with SN 2013cu-we caught the supernova before it overtook the wind. Shortly after the star exploded, it let out an ultraviolet flash from the shock wave that heated and lit up the wind. The conditions that we observed in this moment were very similar to what was there before the supernova."
Since the researchers caught the supernova early, they were able to take several spectra, according to Nugent. He added that they'd like to continue to do this to develop interesting statistics, not just for supernovas with Wolf-Rayet progenitors, but other types.
Research was published in the journal Nature.
"This discovery was totally shocking, it opens up a whole new research area for us," said Nugent. "With our largest telescopes you might have a chance of getting a spectrum of a Wolf-Rayet star in the nearest galaxies to our Milky Way, perhaps 4 million light years away. SN 2013cu is 360 million light years away-further by almost factor of 100."
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