NGC 5139, also known as Omega Centauri, is a globular cluster located in the constellation Centaurus. It is one of the largest and brightest globular clusters visible from Earth, containing millions of stars. NGC 5139 is approximately 15,800 light-years away and has a diameter of about 150 light-years. Discovered by Sir John Herschel in 1834, NGC 5139 is notable for its unique characteristics, including a diverse population of stars with varying metallicities. This cluster is thought to be the remnant core of a dwarf galaxy that was absorbed by the Milky Way, making it an important object for studying the formation and evolution of galaxies.