How to find it
If you’ve never seen the summer Milky Way before, you’re truly missing one of Nature’s greatest spectacles. It is definitely worth your while to travel away from pesky city lights to see the many star clusters and nebulae that beautify a dark summer night. Bring a reclining lawn chair and binoculars with you to take it all in.
We highlight one of the many summer treasures: the Trifid Nebula (Messier 20), a binocular attraction in the constellation Sagittarius the Archer. To locate it, first find The Teapot formation in the western half of Sagittarius. The Teapot is an asterism – a star pattern that is NOT a constellation. Nonetheless, most people have an easier time envisioning the Teapot than the Centaur that Sagittarius is suppose 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.
Photo Credit Trifid Nebula: ESO
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.
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.
The Trifid Nebula (M20) is at RA: 18h 02.6s; Dec: 23o 02′ south