The video shows the expansion of a supernova remnant — a giant cloud of shockwaves and superheated material ejected from the star after it exploded.
This particular supernova, called Tycho's supernova, exploded in 1572, and we can still see the remnant expanding almost 450 years later from our position 10,000 light-years away.
Scientists put together a video of the swelling supernova remnant using observations from the Chandra X-ray Observatory taken from 2000 to 2015:
The shock waves from the supernova makes the remnant extremely hot, and that's why its visible in X-ray light. The video allowed astronomers to calculate how fast the shock wave of the supernova traveled. It's top speed is about 12 million miles per hour.
The speed in turn helps astronomers figure out what triggered the supernova in the first place. In this case, it's likely the supernova happened when two white dwarf stars merged. The merging mega-star was just too huge to stabilize, so it erupted and destroyed both stars in the process.
Studying supernovae is one of the most important ways astronomers calculate how quickly the universe is expanding.