Located in the southern celestial hemisphere, Sagittarius is 1 of 12 the constellations of the zodiac. It is also 1 of the 48 constellations listed by the 2nd-century astronomer Ptolemy and is one of the 88 modern constellations. Sagittarius is Latin for “archer”, and is commonly represented as a centaur pulling back a bow. It lies between Scorpius and Ophiuchus to the west and Capricornus and Microscopium to the east.

The center of the Milky Way lies in the westernmost part of Sagittarius, which means that the galactic center lies in Sagittarius. This mans that the Milky Way is its senses in Sagittarius; therefore, Sagittarius contains many star clusters and nebulae.

As seen from the northern hemisphere, the constellation’s brighter stars form an easily recognizable asterism known as “the Teapot”.

	Applicable Information
Visibility In Pacific Northwest	May To August
Best Times To View	June
Right Ascension	19h
Declination	−25°
Area	867 square degrees
Main Stars	12, 8
Brightest Object	ε Sgr
Meteor showers	0
Messier objects	15
Neighboring Constellations	Aquila, Scutum, Serpens, Cauda, Ophiuchus, Scorpius, Corona Australis, Telescopium, Indus, Microscopium, Capricornus

Mythology

The Babylonians identified Sagittarius as the god Nergal, a centaur-like creature firing an arrow from a bow. Nergal is generally depicted with wings, with two heads, one panther head and one human head, and a scorpion’s stinger raised above its more conventional horse’s tail.

The Sumerian name of Pabilsag is composed of two elements – Pabil, meaning ‘elder paternal kinsman’ and Sag, meaning ‘chief, head’. The name may thus be translated as the ‘Forefather’ or ‘Chief Ancestor’. The figure is reminiscent of modern depictions of Sagittarius.

Greek mythology

In Greek mythology, Sagittarius is usually identified as a centaur: half human, half horse. However, perhaps due to the Greeks’ adoption of the Sumerian constellation, some confusion surrounds the identity of the archer. Some identify Sagittarius as the centaur Chiron, the son of Philyra and Cronus, who was said to have changed himself into a horse to escape his jealous wife, Rhea, and tutor to Jason. As there are two centaurs in the sky, some identify Chiron with the other constellation, known as Centaurus. An alternative tradition holds, that Chiron devised the constellations Sagittarius and Centaurus to help guide the Argonauts in their quest for the Golden Fleece.

There are some competing myths surrounding Sagittarius.

The arrow of this constellation points towards the star Antares, which is the “heart of the scorpion”, and Sagittarius stands poised to attack should Scorpius ever attack the nearby Hercules, or to avenge Scorpius’s slaying of Orion.

On the west side of the constellation, Ptelomy also described the asterism Terebellum consisting of four 4th magnitude stars.

Objects In The Constellation

There are 2 well known star clouds that are great to view in binoculars.

• The Large Sagittarius Star Cloud is the brightest visible region of the Milky Way, and is easily found as it contains the innermost galactic structure that can be observed in visible wavelengths.
• Messier 24 or the Small Sagittarius Star Cloud has an apparent magnitude of 2.5, and fills a significant volume to a depth of 10,000 to 16,000 light-years. There are several objects that are embedded in M24 due to its size.

Sagittarius contains several well-known objects, including Messier 8, Messier 17, and Messier 20.

• The Lagoon Nebula or M8 is an emission nebula that appears grey in telescopes to the unaided eye; however, long-exposure photographs reveal its pink hue, which is common to emission nebulae. It is fairly bright, with an integrated magnitude of 3.0.
• The Omega Nebula, otherwise known as the Horseshoe Nebula or Swan Nebula is a bright and massive star-forming region in the Milky Way galaxy. Its local geometry is similar to the Orion Nebula except that it is viewed edge-on rather than face-on.
• The Trifid Nebula, otherwise known as M20 or NGC 6514) is an unusual combination of an open cluster of stars; an emission nebula (the lower, red portion), a reflection nebula (the upper, blue portion) and a dark nebula. The object is visible in amateur telescopes and is a favorite of amateur astronomers.
• NGC 6537, otherwise known as the Red Spider Nebula is a planetary nebula located roughly 4000 light-years from Earth.
• NGC 6559 is a star-forming region located at a distance of roughly 5000 light-years from Earth.
• Located close to NGC 6640, the planetary nebula NGC 6445 is a large nebula at over one arcminute in diameter, it is also known as the Little Gem Nebula or Box Nebula
• Located 1 degree away from M22 and M28, NGC 6638 is a dimmer globular at magnitude 9.2

Other deep sky objects

Messier 54 was the first globular cluster found that is outside the Milky Way.

The complex radio source Sagittarius A is also in Sagittarius, near its western boundary with Ophiuchus. Astronomers believe that one of its components, known as Sagittarius A, is associated with a supermassive black hole at the center of the galaxy, with a mass of 2.6 million solar masses. Although not visible to the eye, Sagittarius A is located off the top of the spout of the Teapot asterism.

Baade’s Window is an area with very little obscuring dust that shows objects closer to the Milky Way’s center than would normally be visible. Two notable objects that are visible in Baade’s Window are global clusters of NGC 6522 and NGC 6528.

Make sure to check out other articles on the site, including a brief introduction to constellations, other constellation articles, and more!