Sagittarius

Sagittarius is a constellation of the zodiac, the one containing the galactic center.

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. One of the brightest of the star clusters is Messier 55, about 7.5° west of δ Sgr.

The constellation contains nebulae such as the Lagoon Nebula (Messier 8), near λ Sagittarii, the Omega Nebula (Messier 17), also known as the Swan or Horseshoe Nebula, near the border with Scutum; and the Trifid Nebula (Messier 20), a large nebula containing some very young, hot stars. The grouping of Lagoon Nebula, Trifid Nebula, and NGC 6559 is often called the Sagittarius triplet.

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. The Sagittarius Dwarf Elliptical Galaxy is located just outside the Milky Way.

Source: en.wikipedia.org/wiki/Sagittarius - 18.09.2011