- α Sgr (Rukbat, meaning "the archer's knee") despite having the "alpha" appellation, it is not the brightest star of the constellation, magnitude of only 3.96.
- Sagittarii (ε Sgr) ("Kaus Australis," or "southern part of the bow"), magnitude 1.85.
- Sigma Sagittarii (σ Sgr) ("Nunki") is the constellation's second-brightest star at magnitude 2.08. Nunki is approximately 260 light years away. "Nunki" is a Babylonian name of origin, thought to represent the sacred Babylonian city of Eridu on the Euphrates, which would make Nunki the oldest star name currently in use.
- Zeta Sagittarii (ζ Sgr) ("Ascella"), magnitude 2.61, actually a double star whose two components have magnitudes 3.3 and 3.5.
- Delta Sagittarii (δ Sgr) ("Kaus Meridionalis"), magnitude 2.71 and only 85 light years from Earth.
- Eta Sagittarii (η Sgr) is a double star with component magnitudes of 3.18 and 10.
- Beta Sagittarii (Beta Sgr, β Sagittarii, β Sgr) is shared by two star systems, β¹ Sagittarii, with apparent magnitude 3.96, and β² Sagittarii, magnitude 7.4. The two stars are separated by 0.36° in the sky and are 378 light years from earth. Beta Sagittarii, located at a position associated with the forelegs of the centaur, has the traditional name Arkab, meaning "achilles tendon."
- Nova Sagittarii 2015 No. 2 was discovered on March 15, 2015, by John Seach of Chatsworth Island, NSW, Australia. It lies near the center of the constellation. It reached a peak magnitude of 4.3 before steadily fading.
History & Discovery
Sagittarius is one of the largest southern constellations. It is easy to find because it lies on the Milky Way and its brightest stars form an asterism known as the Teapot. Like many other zodiac constellations, Sagittarius was first cataloged by the Greek astronomer Ptolemy in the 2nd century.
The Babylonians identified Sagittarius as the god Nergal, a strange centaur-like creature firing an arrow from a bow. It is generally depicted with wings, with two heads, one panther head and one human head, as well as a scorpion's stinger raised above its more conventional horse's tail.
The Sumerian named Sagittarius Pabilsag, 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 they used to describe Sagittarius is more reminiscent of modern depictions of Sagittarius.
In Greek mythology, Sagittarius is usually identified as a centaur: half human, half horse, perhaps due to the Greeks' adoption of the Sumerian constellation system. Some identify Sagittarius as the centaur Chiron, the son of Philyra and Cronus and tutor to Jason, who was said to have changed himself into a horse to escape his jealous wife, Rhea. However, some identify Chiron with the constellation Centaurus, the other heavenly centaur. An alternative tradition is that Chiron merely invented the constellation Sagittarius to help in guiding the Argonauts in their quest for the Golden Fleece.
A competing mythological tradition, as espoused by Eratosthenes, identified the Archer not as a centaur but as the satyr Crotus, son of Pan, who Greeks credited with the invention of archery. According to myth, Crotus often went hunting on horseback and lived among the Muses, who requested that Zeus place him in the sky, where he is seen demonstrating archery. The arrow of this constellation points towards the star Antares, 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.
Deep Sky Objects
The constellation contains the luminous Pistol Star, the galactic centre, the radio source Sagittarius A, and a number of very famous deep sky objects, including the Sagittarius Dwarf Elliptical Galaxy, the Sagittarius Dwarf Irregular Galaxy, Barnard’s Galaxy, the Bubble Nebula, and as many as 15 Messier objects.
Sagittarius contains 15 Messier objects: