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.
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