A Powerful Shock Wave Traveling
Through a gas cloud left behind by the explosive death of a star has a bizarre quirk: Part of it is traveling in the wrong direction.
Researchers Found That One
Section of the shock wave is collapsing back towards the origin of the stellar explosion, they call it a "Reverse Shock"
Cassiopeia A Is A Nebula
A gas cloud, left behind by a supernova in the constellation Cassiopeia, 11,000 light-years from Earth, making it one of the closest supernova remnants.
The Nebula Is 16 Light-Years Wide
Made of gas (mainly hydrogen) that was expelled both before and during the explosion that ripped apart the original star.
A Shock Wave From That Explosion
Is still rippling through the gas, and theoretical models show that this shock wave should be expanding evenly, like a balloon.
But This Wasn't The Case
"For a long time, we suspected something weird was going on inside Cassiopeia A," Astronomer Jacco Vink. "the internal motions within the nebula were rather chaotic"
After 19 Years Of Data It Was
Confirmed that part of the western region of the shock wave was retreating in the opposite direction in a reverse shock.