What is Omega Centauri?
Omega Centauri, also called NGC 5139, is a dense global cluster of stars that orbits the Milky Way. It is clearly visible from most of the southern hemisphere with the naked eye, located about 18,300 light years from the Earth, or ~18% of the galactic diameter. In 2003 it was proposed that Omega Centauri could be the remnant of a dwarf galaxy hundreds of times its size that was swallowed and ripped apart by the Milky Way many millions of years ago. The age of Omega Centauri is estimated at about 12 billion years, and it is one of few globular clusters which can be seen without the aid of a telescope. Omega Centauri was originally discovered by the astronomer Edmund Halley in 1677. It is the largest and most luminous star cluster associated with the Milky Way, denser than even the Milky Way’s galactic core. The center of Omega Centauri is so dense that stars are only about 0.1 light years (~6000 AU) apart. The cluster has a diameter of approximately 100 light years. Omega Centauri conta
Nearly 2000 years ago, Ptolemy listed it as a star. Then in 1677, Omega Centauri appeared fuzzy to Edmond Halley, so he reported it as a nebula. 153 years later, John Herschel realized that this fuzzy ball is actually composed of individual stars, a globular cluster. And today, new result suggests that Omega Centauri is not a globular cluster at all, but a dwarf galaxy stripped of its outer stars. Omega Centauri (NGC5139). Credit: NASA, ESA, Hubble Heritage Team (STScI/AURA) Omega Centauri has always been a mystery. It has several characteristics that distinguish it from other globular clusters: it rotates faster than other globular cluster, its shape is highly flattened and it consists of several generations of stars – more typical globular clusters usually consist of just one generation of old stars. Moreover, Omega Centauri is about 10 times as massive as other big globular clusters, almost as massive as a small galaxy. These peculiarities have led astronomers to suggest that Omega
