M1, or the Crab Nebula, is the remains of an enourmous explosion which occured in 1054. Since then the gas and dust thrown off in the explosion has been expanding out in a giant shell-like structure. The remnant of the exploded star is known as a pulsar, a very dense compact star spinning many times a second.

This image shows two pulsars as observed with the EGRET gamma-ray instrument on board the Compton Gamma-Ray Observatory. The field of view of this image is much larger than the other images in this section and shows the Crab (bottom right) and Geminga (top left) pulsars, both of which are very bright at these short wavelengths.

Image credit: EGRET