The Trifid Nebula (Messier 20) is one of the many binocular treasures in the summer Milky Way. Its name means divided into three lobes, although you’ll likely need a telescope to see why. On a dark, moonless night, you can star-hop upward from the spout of the Teapot in Sagittarius to another famous nebula, the Lagoon, also known as Messier 8. In the same binocular field, look for the smaller and fainter Trifid Nebula as a fuzzy patch above the Lagoon. Follow the links below to learn more.
How to find the Trifid. To locate this nebula, first find the famous Teapot asterism in the western half of Sagittarius. The Teapot is just a star pattern, not an entire constellation. Nonetheless, most people have an easier time envisioning the Teapot than the Centaur that Sagittarius is supposed to represent.
As seen from mid-northern latitudes, the Teapot is due south and highest in the sky around midnight (1 a.m. daylight saving time) on July 1. Even so, the Teapot never climbs very high in our northern skies, so any obstructions such as trees or mountains may block your view of this landmark star formation. Because the stars return to the same place in the sky some 2 hours earlier with each passing month, the Teapot is highest up around 10 p.m. (11 p.m. daylight saving time) on August 1, and highest at about 8 p.m. (9 p.m. daylight saving time) on September 1.
As shown on our sky chart, we use the three westernmost (right-hand) stars of the Teapot spout to star-hop to the Trifid Nebula. Draw an imaginary line form the spout’s bottom star and in between the spout’s uppermost stars.
Use binoculars and go about twice the spout’s distance upward until a bright hazy object glares at you in your binoculars. That’s the Lagoon Nebula (Messier 8), which is actually visible to the unaided eye on a dark, moonless night.
Once you locate the Lagoon Nebula, look for the smaller Trifid Nebula as a hazy object some 2 degrees above the Lagoon.
For reference, keep in mind that a binocular field commonly spans 5 to 6 degrees of sky.
Trifid science. Whether the close-knit nebulosity of the Trifid and Lagoon Nebulae represents a chance alignment or an actual kinship between the two nebulae is open to question. Both the Trifid and Lagoon Nebulae are thought to reside about 5,000 light-years away, suggesting the possibility of a common origin. But these distances are not known with precision, and may be subject to revision.
Both the Trifid and Lagoon Nebulae are vast cocoons of interstellar dust and gas. These are stellar nurseries, actively giving birth to star formation. The Trifid and Lagoon Nebulae are summertime’s answer to the winter sky’s Great Orion Nebula.
For more about the science of this nebula, see our article on exploring the Trifid Nebula.
Bottom line: The Trifid is a famous summertime binocular object. Its name means “divided into three lobes.” If you view this nebula through a telescope, you’ll see why.
The Trifid Nebula (M20) is at RA: 18h 02.6s; Dec: 23o 02′ south
Bruce McClure has served as lead writer for EarthSky's popular Tonight pages since 2004. He's a sundial aficionado, whose love for the heavens has taken him to Lake Titicaca in Bolivia and sailing in the North Atlantic, where he earned his celestial navigation certificate through the School of Ocean Sailing and Navigation. He also writes and hosts public astronomy programs and planetarium programs in and around his home in upstate New York.