M1, Palomar
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 the nebula in optical light through the Palomar telescope. In this part of the spectrum, the nebula appears very filamentary in nature. The light from the filaments comes from hot gas in shock waves while the diffuse light comes from gas at lower temperatures which has been heated by the pulsar, the remains of the dead star.

Image credit: Palomar