Finder Chart for Jim’s Pick of the Month July 2021 Messier 17: Omega Nebula FACTS Object: Nebula Type: Emission Designations: Omega Nebula, Messier 17, M17, NGC 6618, Sharpless 45, RCW 160, Gum 81, Collinder 377, LBN 60, Swan Nebula, Lobster Nebula, Horseshoe Nebula, Checkmark Nebula Constellation: Sagittarius Right ascension: 18h 20m 26s Declination: -16°10’36” Distance: 5,000-6,000 light years (1,533-1,840 parsecs) Apparent magnitude: +6.0 Image: ESO, 2015 Messier 17 (M17), also known as the Omega Nebula, is a famous star-forming nebula located in the southern constellation Sagittarius. The diffuse emission nebula lies near the constellation’s northern border with Scutum, at a distance of 5,000 to 6,000 light years from Earth. It has an apparent magnitude of 6.0. Also known as the Swan Nebula, Lobster Nebula, Horseshoe Nebula and Checkmark Nebula, the Omega Nebula is one of the brightest star-forming nebulae of the Milky Way. Its designation in the New General Catalogue is NGC 6618. With a total mass of roughly 800 solar masses, M17 is also one of the most massive H II regions of our galaxy. The nebula occupies an area roughly 15 light years in diameter and is part of a larger cloud, which is about 40 light years in diameter. Messier 17 is located in the Sagittarius Arm of the Milky Way, the next inward spiral arm to our own, and may be part of the same giant cloud complex as its close neighbor, Messier 16 (the Eagle Nebula), located in the constellation Serpens. The Omega Nebula is just on the limit of naked eye detection in good conditions, with clear, dark skies and no light pollution. It is best observed in low-powered telescopes and binoculars. It lies in the same binocular field of view as Messier 16 and Messier 18, a faint open cluster in Sagittarius. .