Kepler's Supernova: Huge 17th-Century Star Explosion in Focus

This is the remnant of Kepler's supernova, the famous explosion that was discovered by Johannes Kepler in 1604. 

The red, green and blue colors show low, intermediate and high energy X-rays observed with NASA's Chandra X-ray Observatory, and the star field is from the Digitized Sky Survey.

CREDIT: X-ray: NASA/CXC/NCSU /M.Burkey

Scientists have conducted a postmortem exam on the last gigantic star explosion ever observed by the naked eye in our galaxy, revealing that the supernova was triggered by a compact white dwarf containing more heavy elements than the sun.

The supernova suddenly appeared in the night sky in 1604. Brighter than all other stars and planets at its peak, it was observed by German astronomer Johannes Kepler, who thought he was looking at a new star. Centuries later, scientists determined that what Kepler saw was actually an exploding star, and they named it Kepler's supernova.

The recent cosmic autopsy — made possible by X-ray observations from the Japan-led Suzaku satellite — could help scientists better understand phenomena known as Type Ia supernovae.

Carles Badenes

"Kepler's supernova is one of the most recent Type Ia explosions known in our galaxy, so it represents an essential link to improving our knowledge of these events," Carles Badenes, an assistant professor of physics and astronomy at the University of Pittsburgh, said in a statement from NASA.

Type Ia supernovae are thought to originate from binary systems where one at least one star is a white dwarf — a tiny, superdense core of a star that has ceased undergoing nuclear fusion reactions.

Gas transferred from a "normal" star in the pair may accumulate on the white dwarf, or if both stars in the system are white dwarfs, their orbits around each other may shrink until they fuse together.

In either case, when the white dwarf or white dwarf conglomerate puts on too much weight (around 1.4 times the sun's mass), a runaway nuclear reaction begins inside, eventually leading to a brilliant supernova.