Messier 20 — Emission Nebula in Sagittarius

The Trifid Nebula is a striking combination of emission nebula (red), reflection nebula (blue), and dark nebula (the dark lanes) all in one object, located about 4,100 light-years away in Sagittarius — at roughly the same distance as its neighbor M8 (the Lagoon Nebula). Three prominent dark dust lanes divide the bright emission region into three lobes, giving the nebula its 'trifid' (three-lobed) name. A small open cluster of young stars sits at its center.

Located about 2 degrees north-northwest of M8 (the Lagoon Nebula). The two make an excellent pair in a wide-field eyepiece. In a 4-inch telescope, M20 appears as a round, bright nebula with the three dark lanes visible under good conditions. The blue reflection component to the north is fainter and harder to see visually. An 8-inch or larger telescope under dark skies shows the trifid structure more clearly. A UHC filter helps with the emission component but dims the reflection nebula. Best observed from June through August alongside M8.

Discovered by Charles Messier on June 5, 1764. The common name 'Trifid' was coined by John Herschel, who described the dark lanes dividing the nebula into three parts. Early photographs by Isaac Roberts and Edward Barnard in the late 1800s revealed the full beauty of the nebula, with its unique combination of emission, reflection, and dark nebulae.