A Tour of Kepler's Supernova Remnant
(Credit: NASA/CXC/A. Hobart)
[Runtime: 03:11]

With closed-captions (at YouTube)

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 debris from a star that blew apart about 20,000 light years from Earth in our Milky Way galaxy.

In 1604 early astronomers, including Johannes Kepler who became the object's namesake, noted the supernova explosion that destroyed the star. What Johannes Kepler didn't know then is that the new object he saw was caused by a small dense star that exceeded a mass limit after interacting with a companion star, triggering a thermonuclear explosion. Today, astronomers call this a Type Ia supernova, and they can study the superheated debris expanding into space and glowing brightly in X-ray light.

Researchers estimated the speeds of different clumps in Kepler by analyzing Chandra X-ray spectra, the spreading out of light that gives the amount of X-rays at different wavelengths. This allowed the astronomers to use the Doppler effect to convert changes in the wavelength of features in the X-ray spectrum into speeds along the line of sight from Chandra to the remnant. They combined this information with measurements of the change in position of clumps between Chandra images obtained in 2000, 2004, 2006 and 2014. With this, the astronomers could measure motions perpendicular to our line of sight and then estimate the speeds of each clump.

The high speeds in Kepler are similar to those scientists have seen in supernova explosions in other galaxies only days or weeks after the explosion. This may mean that some clumps in Kepler have hardly been slowed down by collisions with material surrounding the remnant in the approximately 400 years since the explosion.

Scientists are still trying to determine exactly why these clumps in Kepler are moving so fast. It could be that it was a particularly powerful supernova explosion, or perhaps the environment the debris is moving into is less dense in certain spots. Regardless, this object will continue to be something to watch in the years to come.

A Quick Look at Kepler's Supernova Remnant
(Credit: NASA/CXC/A. Hobart)
[Runtime: 1:12]

Astronomers have clocked debris from an exploded star moving at over 20 million miles an hour — about 25,000 times the speed of sound on Earth.

This supernova was first seen on Earth over 400 years ago and today is known as Kepler's supernova remnant.

Kepler's supernova remnant happened when a small dense star exceeds a mass limit by interacting with a companion star and is destroyed in a thermonuclear explosion.

Debris from the explosion has been expanding into space for centuries but remains superheated and glows brightly in X-ray light.

NASA's Chandra X-ray Observatory has been studying Kepler's supernova remnant as it has changed over the years.

This latest study shows different clumps of the material moving away from Earth while a smaller number are directed toward it.

Scientists are still trying to determine why these pieces of stellar debris are still moving so quickly 400 years after the star blew apart.

Kepler's Supernova Remnant Timelapse
(Credit: NASA/CXC/A. Hobart)
[Runtime: 0:49]

This sequence of Chandra images, taken over nearly a decade and a half, captures motion in Kepler's supernova remnant. Pieces of this debris field are still moving at about 23 million miles per hour over 400 years after the explosion was spotted by early astronomers. Scientists are still trying to determine whether an extremely powerful explosion or an unusual environment around it is responsible for these high speeds so long after the explosion. The Kepler supernova was triggered by a white dwarf that reached a critical mass after interacting with a companion star and exploded.

Kepler's Supernova Remnant Features
(Credit: NASA/CXC/A. Hobart)
[Runtime: 0:27]

In the sequence of the four Chandra images of Kepler's supernova remnant, red, green, and blue reveal the low, medium, and high-energy X-rays respectively. The movie zooms in to show several of the fastest moving knots.

The high speeds in Kepler are similar to those scientists have seen in optical observations of supernova explosions in other galaxies only days or weeks after the explosion, well before a supernova remnant forms decades later. This comparison implies that some knots in Kepler have hardly been slowed down by collisions with material surrounding the remnant in the approximately 400 years since the explosion.

Kepler's Supernova Remnant Knots Close-up: N1, N2, and N5
(Credit: NASA/CXC/A. Hobart)
[Runtime: 0:27]

Based on the Chandra spectra, eight of the 15 knots are definitely moving away from Earth, but only two are confirmed to be moving towards it. (The other five do not show a clear direction of motion along our line of sight.) This asymmetry in the motion of the knots implies that the debris may not be symmetric along our line of sight, but more knots need to be studied to confirm this result.

The four knots with the highest total speeds are all located along a horizontal band of bright X-ray emission. Three of them are labeled in the close-up video. These four knots are all moving in a similar direction and have similar amounts of heavier elements such as silicon, suggesting that the matter in all of these knots originated from the same layer of the exploded white dwarf.

Kepler's Supernova Remnant Knots Close-up: "the Ears"
(Credit: NASA/CXC/A. Hobart)
[Runtime: 0:27]

One of the other fastest moving knots is located in the "ear" of the right side of the remnant, supporting the intriguing idea that the three-dimensional shape of the debris is more like a football than a uniform sphere. This knot and two others are labeled with arrows in the close-up shots.