• Kepler's supernova remnants still moving at high speeds 400 years after the explosion
  • The remnants are moving at speeds of 20 million miles per hour
  • That's 25,000 times faster than the speed of sound on Earth

Astronomers have found that the debris from a supernova blast is still moving at extremely high speeds some 400 years after the blast was first observed from Earth.

It was in 1604 that early astronomers, including Johannes Kepler, first observed the supernova explosion we now know as Kepler's Supernova, some 20,000 light years away in the Milky Way. At the time, its greatest apparent magnitude was about -2.5, making it brighter than Jupiter. But by 1606, it was no longer visible to the naked eye.

Today, astronomers still get to observe the phenomenon through advanced means such as NASA’s Chandra X-ray Observatory.

In a recent study published in The Astrophysical Journal, astronomers using Chandra data observed Kepler's supernova remnants and found that debris from the blast were still moving at incredibly high speeds of about 20 million miles per hour.

"This is about 25,000 times faster than the speed of sound on Earth," NASA said in a news release.

Kepler's supernova is a Type 1a supernova, which means that the explosion was a result of a white dwarf star reaching critical mass from accreting material from a companion star. When this happens, the star explodes and propels its materials outward.

"Our measured radial velocities and proper motions indicate that some of these ejecta knots are almost freely-expanding after ~400 years since the explosion," the researchers wrote. 

In fact, the measured speeds of Kepler debris are similar to the observed speeds in supernova explosions just days or weeks after the explosion, suggesting that some knots in Kepler barely slowed down even centuries after the explosion.

In a new sequence of Chandra images that were taken in a span of more than a decade, one can see pieces of the debris field that are still moving at high speeds.

Of the knots the researchers observed, eight out of 15 are certainly moving away from the Earth while two have been confirmed to be moving toward the direction of the Earth. The direction of the other five are unclear from the line of sight from Earth, suggesting an asymmetry in the ejecta distribution.

That said, the researchers note that the study only involved a small sample, thus requiring further and longer studies to confirm the asymmetry. 

Why Kepler's supernova remnants are still moving at such high speeds is unclear, although one possible explanation could be that parts of the remnant environment have low density "windows" through which the fast-moving ejecta may travel. It's also possible that the high speeds could be explained by the Kepler supernova remnants being from an unusually bright Type 1a.

supernova Pictured, a remnant of Kepler's supernova, the famous explosion that was discovered by Johannes Kepler in 1604. The red, green and blue colors show low, intermediate and high energy X-rays observed with NASA's Chandra X-ray Observatory, and the star field is from the Digitized Sky Survey. Photo: X-ray: NASA/CXC/NCSU/M.Burkey et al; Infrared: NASA/JPL-Caltech