Discovered by Charles Messier in 1764^[1,2].

The Trifid Nebula (M20 - NGC 6514) derives its name from the three lobed appearance formed by a dark obscuring cloud of material traversing the red emission nebula^[1,2].  A cluster of very hot young stars at its center of the red emission nebula energizes the nebula^[1].  The blue nebula is a reflection nebula^[2].  The color is due to light from the bright star at its center reflecting from interstellar dust.  The effect is similar to the same phenomena that makes our sky appear blue.

The Trifid is located in the constellation Sagittarius^[1,2].  Distance estimations to M20 vary, however, the NASA Science web site indicates a distance of 9,000 light years^[1].

The open cluster located in the upper left corner of the image is designed M21^[3].  This cluster of stars shows a strong concentration of stars toward its center^[3].  The cluster was classified by Woldemar Gotz as a Trumpler class I 3 r^[3].  The M21 cluster is composed of approximately 57 member stars^[3].