The name M17 stands for the 17th entry in MessierΓÇÖs Catalogue of Diffuse Nebulae. But the nebula has at least three additional names, dating back to the observers who first discovered and studied it: the Swan, Horseshoe, or Omega Nebula. Each name was intended to describe an aspect of the nebulaΓÇÖs appearance. The Swan is perhaps the easiest to understand: if one were to rotate the visible light image to the left it would look somewhat like a swanΓÇÖs profile. M17ΓÇÖs horseshoe or omega (a Greek letter that resembles a horseshoe) wraps around the bill and head of the swan. Seeing shapes in nebulae is not unlike seeing them in clouds. A nebula is really just a giant cloud of gas in the heavens. But while clouds in the sky change
