NASA’s planet hunter, the Kepler space telescope, has captured the brilliant flash of an exploding star’s shock wave—what astronomers call the “shock breakout” of a supernova—for the first time in visible light wavelengths.
An international science team, including two astronomers from the University of Maryland, analyzed light captured by Kepler every 30 minutes over a three-year period, searching some 50 trillion stars spread across 500 distant galaxies. The astronomers were hunting for signs of massive stellar death explosions known as supernovae.
To put their size into perspective, Earth’s orbit about our sun would fit comfortably within these colossal stars,” said Peter Garnavich, an astrophysics professor at the University of Notre Dame in Indiana who led the analysis efforts.
Whether it’s a plane crash, car wreck or supernova, capturing images of sudden, catastrophic events is extremely difficult but tremendously helpful for understanding the event’s root cause. The steady gaze of Kepler allowed astronomers to see, at last, a supernova shock wave 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.
“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 shock wave from the stellar core reached the surface of the star,” said Edward Shaya, an associate research scientist in astronomy at UMD and a co-author on the study. “These events are bright enough that they change the brightness of the whole galaxy by a measurable amount.”
Supernovae like these—known as Type II—begin when the internal furnace of a star runs out of nuclear fuel, causing its core to collapse as gravity takes over. The two supernovae matched up well with mathematical models of Type II explosions, thus reinforcing some existing theories.
But the supernovae also revealed an unexpected variety in these cataclysmic stellar events. While both explosions delivered a similar energetic punch, no shock breakout was seen in the smaller of the two supergiants. Scientists think this is likely due to the smaller star being surrounded by gas—perhaps enough to mask the shock wave when it reached the star’s surface.
“That is the puzzle of these results,” said Garnavich. “You look at two supernovae and see two different things. That’s maximum diversity.”
Studying the physics of these violent events allows scientists to better understand how the seeds of chemical complexity and life itself have been scattered in space and time in our Milky Way galaxy.
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