Sagittarius

Sagittarius is one of the constellations of the zodiac. It is one of the 48 constellations listed by the 2nd-century astronomer Ptolemy and remains one of the 88 modern constellations. Its name is Latin for the archer, and its symbol is ♐, a stylized arrow. Sagittarius is commonly represented as a centaur drawing a bow. It lies between Scorpius and Ophiuchus to the west and Capricornus to the east. ... As seen from the northern hemisphere, the constellation's brighter stars form an easily recognizable asterism known as 'the Teapot'. The stars δ Sgr (Kaus Media), ε Sgr (Kaus Australis), ζ Sgr (Ascella), and φ Sgr (Nanto) form the body of the pot; λ Sgr (Kaus Borealis) is the point of the lid; γ2 Sgr (Alnasl) is the tip of the spout; and σ Sgr (Nunki) and τ Sgr the handle (the closest bright star to the possible origin of the Wow! signal.) Marking the bottom of the teapot's "handle" (or the shoulder area of the archer, are the bright star (2.59 magnitude) Zeta Sagittarii (ζ Sgr), named Ascella, and the fainter Tau Sagittarii (τ Sgr). To complete the teapot metaphor, under good conditions, a particularly dense area of the Milky Way can be seen rising in a north-westerly arc above the spout, like a puff of steam rising from a boiling kettle. The constellation as a whole is often depicted as having the rough appearance of a stick-figure archer drawing its bow, with the fainter stars providing the outline of the horse's body. Sagittarius famously points its arrow at the heart of Scorpius, represented by the reddish star Antares, as the two constellations race around the sky. Following the direct line formed by Delta Sagittarii (δ Sgr) and Gamma Sagittarii (γ Sgr) leads nearly directly to Antares. Fittingly, Gamma Sagittarii is named Alnasl, the Arabic word for "arrowhead," and Delta Sagittarii is called Kaus Media, the "center of the bow," from which the arrow protrudes. Kaus Media bisects Lambda Sagittarii (λ Sgr) and Epsilon Sagittarii (ε Sgr), whose names Kaus Borealis and Kaus Australis refer to the northern and southern portions of the bow, respectively. ... the brightest star is Epsilon Sagittarii (ε Sgr) ("Kaus Australis," or "southern part of the bow"), at magnitude 1.85. Sigma Sagittarii (σ Sgr) ("Nunki") is the constellation's second-brightest star at magnitude 2.08. Nunki is a B2V star approximately 260 light years away. "Nunki" is a Babylonian name of uncertain origin, but 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"), with apparent magnitude 2.61 of A2 spectra, is actually a double star whose two components have magnitudes 3.3 and 3.5. Delta Sagittarii (δ Sgr) ("Kaus Maridionalis"), is a K2 spectra star with magnitude 2.71 and only 85 light years from Earth. ... The Milky Way is at its densest near Sagittarius, as this is where the galactic center lies. Consequently, Sagittarius contains many star clusters and nebulae. ... Sagittarius contains several well-known nebulae, including the Lagoon Nebula (Messier 8), near λ Sagittarii; the Omega Nebula (Messier 17), also known as the Horseshoe Nebula or Swan Nebula, near the border with Scutum; and the Trifid Nebula (Messier 20), a large nebula containing some very young, hot stars. ... In 1999 a violent outburst at V4641 Sgr was thought to have revealed the location of the closest known black hole to Earth, but later investigation increased its estimated distance by a factor of 15. The complex radio source Sagittarius A is also here. 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. The Sagittarius Dwarf Elliptical Galaxy is located just outside the Milky Way. [Sagittarius (constellation). Wikipedia]