The “Black Widow” pulsar is moving through the galaxy at a speed of almost a million kilometers per hour. A bow shock wave due to this motion is visible to optical telescopes, shown in this image as the greenish crescent shape. The pressure behind the bow shock creates a second shock wave that sweeps the cloud of high-energy particles back from the pulsar to form the cocoon.
Great end of year gift to students :) What a fun idea! Give each student a sheet of paper with every classmate's name on it. They have to write a nice sentence about everyone, then each student has 20+ nice things written about him or her. Some students don't hear about how great they are at home, so this can be a much-needed pep talk. Collect them all in a frame to preserve them. Kids will love hearing about how great they are from classmates.