The Expansion of the Crab Nebula (2003-2020)

About This Photograph

Here is a comparison of two photographs of the Crab Nebula, one taken in 2003 and the other in 2020, showing the dramatic expansion of this supernova remnant. At a distance of 6,500 light years, for visible changes to be taking place in the astronomically short time of 17 years means this stuff is moving really fast. Measuring the motion of the outer features, I calculate that the material around the short axis is moving outward at about 700 miles per *second*, while the material along the long axis is hurtling along at about 980 miles per second. That's around 0.5% the speed of light!

A few others stars in this area also have high "proper motion," which is the part of their motion perpendicular to our line of sight. The Crab Pulsar itself (the faint star near the center of the nebula) is also moving at around 180 miles per second, at least in terms of proper motion... it might also be moving toward or away from us. When it blew up, the explosion was apparently asymmetric and gave the dying star a hefty kick in one direction.