Mach 1000 Shock Wave Lights Tycho's Supernova Remnant

Astronomers have finally discovered what makes the supernova material shine so brightly even after hundreds of years after explosion.

When a star explodes as a supernova, it shines brightly for several weeks or months before disappearing. But the material that is emitted out from the explosion continues to glow for hundreds of years after the explosion.  Scientists till date did not know what made the remnants glow.

Astronomers at the Harvard-Smithsonian Center for Astrophysics have found that reverse shock waves in supernovas that race inwards at the speed of 1000 Mach is what actually heats the remnants and triggers the release of X-ray light.

W"e 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).

It was in 1572 that an astronomer Tycho Brahe discovered the supernova Tycho. But what was even more interesting was the bright glow. The supernova was the brightest and it even surpassed Venus and finally faded after a year.

Modern astronomers classify the Tycho as a Type Ia supernova, which occurs when a white dwarf star explodes.  It emitted elements like silicon and iron into the outer space at speeds of more than 11 million miles per hour. And when this material collided with the nearby interstellar gas, it formed a sonic boom i.e. a shock wave. This shock wave propell outward till today at about Mach 300. This collision also triggered a backwash with inward speed of  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.

The gases present inside the supernova remnant are heated due to the reverse shock and this causes them to glow. This mechanism is similar to that found in household fluorescent bulbs. The only difference is that the remnant of supernova glows in X-rays instead of the visible light.

The X-ray spectrum of the supernova remnant was studied using the Suzaku spacecraft. This is the first evidenced of the collision less electron heating in reverse shock  the remnants of Tycho's supernova.

"Thanks to the reverse shock, Tycho's supernova keeps on giving," Smith says.