The diffuse nebula M17 in Sagittarius, also known as NGC 6618; alternative names are the Horseshoe Nebula and the Swan Nebula. The Omega Nebula is ¾° across at its widest, and is variously described as being shaped like a Greek letter omega, a horseshoe, a swan, or the figure 2. It lies about 5000 l.y. away.
Subjects: Astronomy and Astrophysics.