New observations of the famous Tycho’s supernova remnant by the Suzaku X-ray astronomy satellite have revealed that a reverse shock wave racing inward at 1,000 times the speed of sound is heating the remnant and causing it to emit X-ray light.
This composite image shows the Tycho supernova remnant. Image credit: X-ray – NASA / CXC / Rutgers / K. Eriksen et al.; optical: DSS.
The Tycho’s supernova, also known as SN 1572 or Tycho’s Nova, was discovered by the Danish astronomer Tycho Brahe in November 1572.
Modern astronomers know that the event 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 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 300 times the speed of sound.
The interaction also created a violent backwash – a reverse shock wave that speeds inward at 1,000 times the speed of sound.
“It’s like the wave of brake lights that marches up a line of traffic after a fender-bender on a busy highway,” explained Dr Randall Smith of the Harvard-Smithsonian Center for Astrophysics, who is the senior author of the paper submitted for publication in the Astrophysical Journal (arXiv.org).
The reverse shock wave heats gases inside the supernova remnant and causes them to fluoresce. The process is similar to what lights household fluorescent bulbs, except that the supernova remnant glows in X-rays rather than visible light.
The reverse shock wave is what allows astronomers to see supernova remnants and study them, hundreds of years after the supernova occurred.
“Thanks to the reverse shock, Tycho’s supernova keeps on giving,” Dr Smith said.
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Bibliographic information: Hiroya Yamaguchi et al. 2013. New Evidence for Efficient Collisionless Heating of Electrons at the Reverse Shock of a Young Supernova Remnant. ApJ, submitted for publication; arXiv: 1310.8355
