NGC 5139 is the largest and most spectacular globular cluster in the entire night sky, and the largest in our galaxy. At 36 arc minutes, Omega Centauri is larger than the full moon in apparent size. It is located about 17,000 light years away from our Sun and at 4th magnitude, is easily visible without a telescope as a "star" in the constellation of Centaurus. It contains about 2 millions stars, nearly twice as many as M13. The stars in globular clusters are generally older, redder and less massive than our Sun. There are more than 200 known globular clusters in our galaxy.