For the first time, scientists caught a pair of supernovae in the act of exploding, watching as supersonic shockwaves reached their surfaces in the moments after explosions took place deep within their cores and observing a never-before-seen “shock breakout” in visible light.
In research currently available online and accepted for publication in the Astrophysical Journal, University of Notre Dame astrophysics professor Peter Garnavich and an international group of colleagues explained that they detected transient events from the Type II-P supernovae during a three-year period in which they studied trillions of stars using the Kepler space telescope.
When stars 10 to 20 times more massive than our sun near the end of their lifespans, they grow to be supergiants, and when they run out of fuel in the cores, their centers collapse as they turn into neutrons stars. At this point, a supersonic shockwave blows up the star, and as it reaches the surface, it was thought to create a bright flash of light called a “shock breakout.”
“The flash from a breakout should last about an hour,” Garnavich said in a statement, “so you have to be very lucky or continuously stare at millions of stars just to catch one flash.”
Research could explain chemical distribution in the Milky Way
Whether it was luck, the fruits of their labor or a little of both, the Notre Dame professor and his fellow astrophysicists were able to observe a shock breakout in 2011 while monitoring a pair of red supergiants – KSN 2011a, which is roughly 300 times more massive than our sun, and KSN 2011d, which is 500 times the size of the sun, exploded while in Kepler’s view.
Both KSN 2011a, with is located just 700 million light years from Earth, and KSN 2011d, which is 1.2 billion light years away, formed Type II-P supernovae following the collapse of their cores. Learning more about the physics of these explosions will allow researchers to better understand how complex chemicals have been scattered throughout the Milky Way.
According to their study, the researchers determined that KSN 2011a’s progenitor radius was “significantly smaller” than that of KSN 2011d, but that each of them “have similar explosion energies.” The rising light curve of the latter supernova was said to be “an excellent match” to simulation-based predictions, while KSN 2011a’s was faster than expected, which Garnavich’s team believes may be due to the shockwave “moving into pre-existing wind or mass-loss.”
“No shock breakout emission is seen in KSN2011a, but this is likely due to the circumstellar interaction suspected in the fast rising light curve,” the authors said. “The early light curve of KSN2011d does show excess emission consistent with model predictions of a shock breakout. This is the first optical detection of a shock breakout from a type II-P supernova.”
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Image credit: University of Notre Dame
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