The
Trifid Nebula (catalogued as
Messier 20 or
M20 and as
NGC 6514) is an
H II region in the north-west of
Sagittarius in a
star-forming region in the
Milky Way'sScutum-Centaurus Arm. It was discovered by
Charles Messier on June 5, 1764. Its name means 'three-lobe'. The object is an unusual combination of an
open cluster of
stars, an
emission nebula (a relatively dense, red-yellow portion), a
reflection nebula (the mainly
NNE blue portion), and a
dark nebula (the apparent 'gaps' in the former that cause the trifurcated appearance also designated
Barnard 85). Viewed through a small
telescope, the Trifid Nebula is a bright and peculiar object, and is thus a perennial favorite of amateur astronomers.The most massive star that has formed in this region is HD 164492A, an
O7.5III star with a mass more than 20 times the
mass of the Sun. This star is surrounded by a cluster of approximately 3100 young stars.
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