Mark Megahan
The only reason there’s something left to see is because the blast was so furious the shrapnel hit a traffic jam. That formed what astronomers like to call a “reverse shock wave.” NASA’s Chandra X-ray Observatory took a hard look at the remnants of a “Type 1a” star explosion recently.
Reverse shock wave echoes back
Everybody loves a good supernova. There’s something really cool about stellar annihilation. The images make great posters too. Reverse shock waves don’t happen over night.
Some astronomers lucky enough to draw some Chandra X-ray Observatory time used it for a hard look at supernova remnant G344.7-0.1. They picked that one because it’s a lot more mature and interesting to look at.
G344 is currently 19,600 light-years from Earth and the explosion event “is about 3,000 to 6,000 years old in Earth’s time frame.” It’s taken that long for the shock wave to echo back all the way to where the core was.
They’re looking to see if that will generate another bounce back out, causing the cluster of radioactive dust to “ring” like a huge bell.
Thanks to the energy generated by the shock wave, astronomers can observe the X-ray light coming from the elements leftover and use it to form a “new composite image” of the remnant. To make a supernova, you start with a white dwarf star.
The Type 1a variety explosion starts with a stable white dwarf that had captured a companion star. Scientists are aware of three more like that in our general vicinity.
Unstably massive
After sucking matter from the companion like a glutton at an all you can eat buffet, G344 had one bite too many and exploded. In the center was left behind the heavy iron and silicon core while everything else vaporized outward into space.
“The debris from the explosion also encountered resistance from surrounding gas, in turn creating the reverse shock wave.” The Chandra team “likens this process to a traffic jam where the debris are the ‘cars’ that back up in the reverse direction of the jam.”
To get the composite image, the team used “three different bands of the electromagnetic spectrum—including X-ray, infrared, and radio.”
The dense center of iron atoms shines bright, surrounded by “arc-like” structures of pure silicon atoms. The other Type 1a’s in the area are Kepler, Tycho, and SN 1006. It’s only illuminated because of the energy produced by the shock wave.
The other three Type 1a supernovae “all appeared from our point of view on Earth only within the last thousand years or so.” They are a lot harder to see “having incomplete reverse shock waves.”
That didn’t stop the experts from creating some spectacular false-color images of all three remnants side-by-side for comparison.
