Debris from Stellar Explosion Not Slowed After 400 Years

On October 8, 1604, a Supernova named "Kepler's nova" was first sighted by Lodovico delle Colombe in Italy. From the article:

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Aug 19, 2020
Kepler's Supernova Remnant: Debris from Stellar Explosion Not Slowed After 400 Years
Kepler's Supernova Remnant.
Astronomers have used NASA's Chandra X-ray Observatory to record material blasting away from the site of an exploded star at speeds faster than 20 million miles per hour. This is about 25,000 times faster than the speed of sound on Earth.

The Kepler supernova remnant is the debris from a detonated star that is located about 20,000 light years away from Earth in our Milky Way galaxy. In 1604 early astronomers, including Johannes Kepler who became the object's namesake, saw the supernova explosion that destroyed the star.

We now know that Kepler's supernova remnant is the aftermath of a so-called Type Ia supernova, where a small dense star, known as a white dwarf, exceeds a critical mass limit after interacting with a companion star and undergoes a thermonuclear explosion that shatters the white dwarf and launches its remains outward.

The latest study tracked the speed of 15 small "knots" of debris in the Kepler supernova remnant, all glowing in X-rays. The fastest knot was measured to have a speed of 23 million miles per hour, the highest speed ever detected of supernova remnant debris in X-rays. The average speed of the knots is about 10 million miles per hour, and the blast wave is expanding at about 15 million miles per hour. These results independently confirm the 2017 discovery of knots travelling at speeds more than 20 million miles per hour in the Kepler supernova remnant."