Discovered by Charles Messier in 1764.
The Trifid Nebula derives its name from the three lobed appearance formed by a dark obscuring cloud of material traversing the red emission nebula. A cluster of very hot young stars at its center energizes the nebula. The blue nebula is a reflection nebula. 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 small open cluster located in the upper left corner of the image is designed M21. The Trifid is located in the constellation Sagittarius approcimately 5,200 light-years from the Earth.