A new video shows the evolution of Kepler’s Supernova Remnant using data from NASA’s Chandra X-ray Observatory captured over more than two and a half decades.

Kepler’s Supernova Remnant, named after the German astronomer Johannes Kepler, was first spotted in the night sky in 1604. Today, astronomers know that a white dwarf star exploded when it exceeded a critical mass, after pulling material from a companion star, or merging with another white dwarf. This kind of supernova is known as a Type Ia, and scientists use it to measure the expansion of the universe.

Supernova remnants, the debris fields left behind after a stellar explosion, often glow strongly in X-ray light because the material has been heated to millions of degrees from the blast. The remnant is located in our galaxy, about 17,000 light-years from Earth, allowing Chandra to make exquisite, detailed images of the debris and how it changes with time. This latest video includes its X-ray data from 2000, 2004, 2006, 2014, and 2025. This makes it the longest-spanning video that Chandra has ever released, enabled by Chandra’s longevity. Only Chandra, with its sharp X-ray images and longevity, can see changes like those seen here.

“The plot of Kepler’s story is just now beginning to unfold,” said Jessye Gassel, a graduate student at George Mason University in Virginia, who led the work. “It’s remarkable that we can watch as these remains from this shattered star crash into material already thrown out into space.” Gassel presented the new Chandra video and the associated research at the 247th meeting of the American Astronomical Society in Phoenix.

The researchers used the video to show that the fastest parts of the remnant are traveling at about 13.8 million miles per hour (2% of the speed of light), moving toward the bottom of the image. Meanwhile, the slowest parts are traveling toward the top at about 4 million miles per hour (0.5% of the speed of light). This large difference in speed is because the gas that the remnant is plowing into toward the top of the image is denser than the gas toward the bottom. This gives scientists information about the environments into which this star exploded.

“Supernova explosions and the elements they hurl into space are the lifeblood of new stars and planets,” said Brian Williams of NASA’s Goddard Space Flight Center in Greenbelt, Maryland, and principal investigator of the new Chandra observations of Kepler. “Understanding exactly how they behave is crucial to knowing our cosmic history.”

The team also examined the widths of the rims forming the blast wave of the explosion. The blast wave is the leading edge of the explosion and the first to encounter material outside of the star. By measuring how wide it is and how fast it is traveling, astronomers glean more information about both the explosion of the star and its surroundings.

NASA's Marshall Space Flight Center in Huntsville, Alabama, manages the Chandra program. The Smithsonian Astrophysical Observatory's Chandra X-ray Center controls science operations from Cambridge, Massachusetts, and flight operations from Burlington, Massachusetts.