Washington: Astronomers have discovered that a reverse shock wave racing inward at Mach 1,000 (1,000 times the speed of sound) is heating the remnant of Tycho`s supernova and causing it to emit X-ray light.
"We wouldn`t be able to study ancient supernova remnants without a reverse shock to light them up," Hiroya Yamaguchi, who conducted this research at the Harvard-Smithsonian Center for Astrophysics (CfA), said.
Tycho`s supernova was witnessed by astronomer Tycho Brahe in 1572.
The appearance of this "new star" stunned those who thought the heavens were constant and unchanging. At its brightest, the supernova rivaled Venus before fading from sight a year later.
Modern astronomers know that the event Tycho and others observed was a Type Ia supernova, caused by the explosion of a white dwarf star.
The explosion spewed elements like silicon and iron into space at speeds of more than 11 million miles per hour (5,000 km/s).
When that ejecta rammed into surrounding interstellar gas, it created a shock wave-the equivalent of a cosmic "sonic boom."
That shock wave continues to move outward today at about Mach 300. The interaction also created a violent "backwash"-a reverse shock wave that speeds inward at Mach 1,000.
"It`s like the wave of brake lights that marches up a line of traffic after a fender-bender on a busy highway," CfA co-author Randall Smith said.
The team studied the X-ray spectrum of Tycho`s supernova remnant with the Suzaku spacecraft.
The findings are set to be published in The Astrophysical Journal.