New Image Details Jewel in Southern Sky
The globular cluster Omega Centauri — with as many as ten million stars — is seen in all its splendour in this image captured with the WFI camera from ESO's La Silla Observatory.
Credit: ESO/EIS

A cluster of stars called Omega Centauri shines like a jewel of the southern hemisphere night sky. It is visible to the naked eye, but through a telescope, millions of stars are revealed to be part of this globular cluster.

A new image shows Omega Centauri in all its splendor.

The object, catalogued as a globular cluster, is roughly 17,000 light-years from Earth in the constellation of Centaurus. It may in fact be the heart of what was once a small galaxy that was destroyed in an interaction with our own Milky Way Galaxy.

Omega Centauri is nearly as large as the full moon in our sky, though much dimmer. It shines about magnitude 3.7, equal to a rather dim star on the astronomer's scale of brightness. Omega Centauri is about 150 light-years across and is the most massive of all the Milky Way's globular clusters. It is thought to contain about 10 million stars.

The new image was made by the Wide Field Imager (WFI), mounted on the 2.2-meter diameter Max-Planck/ESO telescope, located at the European Southern Observatory's La Silla facility, high up in the arid mountains of the southern Atacama Desert in Chile.

Omega Centauri has been observed throughout history. Both the great astronomer Ptolemy and later Johann Bayer catalogued the cluster as a star. It was not until much later, in the early 19th century, that an Englishman, the astronomer John Frederick William Herschel (son of the discoverer of Uranus), realized that Omega Centauri was in fact a globular cluster, ESO astronomers explain. Globular clusters are some of the oldest groupings of stars to be found in the halos that surround galaxies like our own Milky Way.

Omega Centauri is thought to be around 12 billion years old. The entire universe is said to be 13.7 billion years old.

Recent research into this intriguing celestial giant suggests that there is a medium sized black hole sitting at its center. Observations made with the Hubble Space Telescope and the Gemini Observatory showed that stars at the cluster's center were moving around at an unusual rate. Astronomers concluded this was caused by the gravitational effect of a massive black hole with a mass of roughly 40,000 times that of the sun.

Regular galaxies typically have black holes weighing in at millions or even billions of solar masses.