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 to the upper left 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 distance to M20 is not known with any certainty. The range of estimated distances is from 2,200 light years to as much as 9,000 light years. The Sky Catalog 2000 assigns a distance of 5,200 light years.