The intense flash of an exploding star’s shockwave (shock breakout) of a supernova has been captured for the first time in visible light wavelengths. The capture was made by the Kepler space telescope, NASA’s planet hunter.
The international team of scientists analyzed light that was captured by Kepler every 30 minutes over a three-year period. They were probing around 50 trillion stars that were spread across 500 distant galaxies, searching for any signs of supernovae (massive stellar death explosions).
Two massive stars, called red supergiants, exploded while in Kepler’s view in 2011. The first one called KSN 2011a, is almost 300 times the size of our sun and is 700 million light years from Earth. With the second called KSN 2011d, being around 500 times the size of our sun, and sits about 1.2 billion light years away.
“The brilliant flash of an exploding star’s shock wave, or ‘shock breakout,’ is illustrated in the video below from NASA’s Ames Research Center. The animation begins with a view of the red supergiant star KSN 2011d. As the star’s internal furnace can no longer sustain nuclear fusion, its core then collapses under its own gravity, thus, forming a supernova.
“The shockwave from the implosion then rushes outward through the star’s layers, firstly breaking through the star’s visible surface as a series of finger-like plasma jets. Then 20 minutes later, the full ferocity of the shockwave reaches the surface, which blasted apart the doomed star.”
Peter Garnavich, an astrophysics professor at the University of Notre Dame in Indiana who led the analysis efforts, said:
“To put their size into perspective, Earth’s orbit about our sun would fit comfortably within these colossal stars.”
According to the University of Maryland the steady gaze of Kepler allowed astronomers to see, at last, a supernova shockwave as it reached the surface of a star. Catching this flash of energy is an investigative milestone for astronomers, because the shock breakout only lasts about 20 minutes.
Edward Shaya, an associate research scientist in astronomy at UMD and a co-author on the study, said in a statement:
“Like police getting surveillance footage of a crime after the event, we can study brightness histories from Kepler to find out what was happening in the exact hour that the shockwave from the stellar core reached the surface of the star.
“These events are bright enough that they change the brightness of the whole galaxy by a measurable amount.”
Supernovae such as these ones are known as Type II, and they begin when the internal furnace of a star runs out of its nuclear fuel, which causes its core to collapse as gravity takes over. These two Supernovae matched with the mathematical models of Type II explosions reinforces some of the existing theories.
However, the supernovae have also revealed an unexpected variety in these catastrophic stellar events. Even though both of the explosions delivered a similar energetic punch, there was no shock breakout seen in the smaller of the two supergiants.
This left the scientists believing that it was likely due to the smaller star being surrounded by gas. Perhaps there was enough to mask the shockwave when it reached the star’s surface. Garnavich said:
“That is the puzzle of these results. You look at two supernovae and see two different things. That’s maximum diversity.”
By studying the physics of these violent events, scientists will gain a better understanding on how the seeds of chemical complexity and life itself have been scattered in space and time in our Milky Way galaxy, the University wrote in a news release.
Steve Howell, project scientist for NASA’s Kepler and K2 missions at NASA’s Ames Research Center in California’s Silicon Valley, said:
“All heavy elements in the universe come from supernova explosions. For example, all the silver, nickel, and copper in the earth, and even in our bodies, came from the explosive death throes of stars.
“Life exists because of supernovae.”
Garnavich, Shaya, and co-authors are part of a research the team known as the Kepler Extragalactic Survey (KEGS).
The team has almost finished mining data from Kepler’s primary mission, which ended in 2013. However, with the reboot of the Kepler spacecraft as NASA’s K2 mission, the team is now hunting for supernova events in other distant galaxies, according to the University.
“It is a thrill to be a part of theoretical predictions becoming an observed and tested phenomenon,” Shaya said. “We now have more than just theory to explain what happens when a supernova shockwave reaches the surface of a star as that star is totally torn apart.”