Astronomers have identified what appears to be a cosmic smoking gun for a historic supernova explosion, a find that may also help with the search for elusive dark energy in the universe.

The new evidence suggests the famed Tycho supernova, located about 13,000 light-years from Earth, formed when its parent star stripped too much material from a nearby companion, forcing it to detonate in a massive thermonuclear explosion. The find was made using NASA's Chandra X-ray Observatory.
A study of the exploded star's remains also suggests that, in general, stars could survive the intense impact generated when their stellar companions undergo a violent supernova death.
The Tycho supernova remnant was first observed in 1572 by the Danish astronomer Tycho Brahe. The object, dubbed Tycho for short, was formed by a Type Ia supernova, which is a category of stellar explosion whose reliable brightness helps scientists measure astronomical distances.
Type Ia supernovas have been used as guideposts in gauging the rate of expansion of the universe – an effect attributed to the prevalence of an invisible, repulsive force throughout space called dark energy.
“There has been an ongoing long-standing question about what causes Type Ia supernovas,” said Fangjun Lu, of the Institute of High Energy Physics at the Chinese Academy of Sciences in Beijing. “Because they are used as steady beacons of light across vast distances, it is critical to understand what triggers them.”
While studying the Tycho supernova with the Chandra observatory, researchers found an arc of X-ray emission in the supernova remnant.
This arc, the researchers suspect, was created by the shock wave generated when a white dwarf exploded (the original Tycho star explosion) and blasted material off the surface of a nearby companion star.
In the past, astronomers have come up with different ideas about what triggers Type Ia supernovas. One popular scenario involves the merger of two, small white dwarf stars.  
(White dwarfs are stars that have exhausted their nuclear fuel and are near the end of their life. That accounts for their low luminosity.) In this white dwarf scenario, no companion star or evidence of material blasted off a companion star should exist after the initial explosion.
In the other main competing theory, a white dwarf draws material off of a “normal,” or sun-like, companion star until a thermonuclear explosion occurs.
While both supernova scenarios could occur under different conditions, the latest observations of Tycho from Chandra suggest that the latter theory is the most likely, researchers said. Can companion stars survive a supernova?
The new study of Tycho also appears to show the incredible resilience of stars, as the supernova explosion appears to have blasted only a small amount of material off the companion star.
(Source: Space.com)