Mach 1000 Shock Wave Lights Supernova Remnant

What is the Mach 1000 Shock wave When a star explodes as a supernova, it shines brightly for a few weeks or months before fading away. Yet the material blasted outward from the explosion still glows hundreds or thousands of years later, forming a picturesque supernova remnant. What powers such long-lived brilliance?

In the case of Tycho's supernova remnant, astronomers have discovered that a reverse shock wave racing inward at Mach 1000 (1000 times the speed of sound) is heating the remnant 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," says Hiroya Yamaguchi, who conducted this research at the Harvard-Smithsonian Center for Astrophysics (CfA)



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 1000.

"It's like the wave of brake lights that marches up a line of traffic after a fender-bender on a busy highway," explains CfA co-author Randall Smith.