The Omega Nebula, also known as the Swan Nebula (catalogued as Messier 17 or M17 and as NGC 6618) is an w:H II region in the w:constellation Sagittarius. It was discovered by w:Philippe Loys de Chéseaux in 1745. w:Charles Messier catalogued it in 1764. It is located in the rich w:starfields of the Sagittarius area of the w:Milky Way.

Omega Nebula
Omega Nebula from w:Hubble Space Telescope
Credit: w:NASA/w:ESA/w:STScI
Observation data: w:J2000 epoch
Right ascension18h 20m 26s[1]
Declination−16° 10′ 36″[1]
Distance5,000-6,000 ly
Apparent magnitude (V)+6.0[1]
Apparent dimensions (V)11 arcmins
Physical characteristics
Absolute magnitude (V)-
Notable features-
Other designationsM17, NGC 6618,
Swan Nebula[1], Sharpless 45, RCW 160, Gum 81

The Omega Nebula is between 5,000 and 6,000 w:light-years from w:Earth and it spans some 15 light-years in diameter. The cloud of interstellar matter of which this w:nebula is a part is roughly 40 light-years in diameter. The total w:mass of the Omega Nebula is an estimated 800 w:solar masses.

A cluster of 35 stars lies embedded in the nebulosity and causes the w:gases of the nebula to shine due to radiation from these hot, young stars.

Three-colour composite image of the Omega Nebula (Messier 17, or NGC 6618). Credit w:ESO

External links


  1. a b c d "SIMBAD Astronomical Database". Results for NGC 6618. Retrieved 2006-11-16.