Credits: Mount Lemmon SkyCenter and University of Arizona

Until the early 1970's, the nebula was thought to be a supernova remnant.
However, Soviet astronomers in 1971 concluded that it was most likely a planetary nebula.

Facts about SH2-274 by Keith Turnecliff

Medusa was a hideous creature with snakes in place of hair. These snakes are represented by the serpentine filaments of glowing gas in this nebula.
The red glow from hydrogen and the fainter green emission from oxygen gas extends well beyond this frame, forming a crescent shape in the sky.
The ejection of mass from stars at this stage of their evolution is often intermittent, which can result in fascinating structures within planetary nebulae.