Post by glactus on Apr 26, 2009 5:37:17 GMT
Omega Centauri
The Globular star cluster Omega Centauri is some 15,000 light-years away in the constellation of Centaurus. This beautiful cluster is 150 light-years in diameter. The cluster is estimated to be about 12 billion years old, and has Magnitude at 3.7
Packed with about 10 million stars, Omega Centauri is the largest of 200 or so known globular clusters that roam the halo of our Milky Way galaxy.
Designated as NGC 5139, Omega Centauri orbits the Milky Way and was discovered by Edmond Halley in 1677, but it was not until The 1830's that the English astronomer John William Herschel recognized it as a globular cluster and listed it in that period.
The cluster is one of the few that can be seen with the naked eye, and is both the brightest and the largest known globular cluster associated with our galaxy having stars in its center so crowded that they are believed to be only 0.1 light years away from each other.
It has been speculated that Omega Centauri may be the core of a dwarf galaxy several hundred times its present size, which was ripped apart and absorbed by the killer Milky Way galaxy.
In April, 2008 astronomers claimed to have found evidence of a intermediate-mass black hole at the center of Omega Centauri. The observations were made with NASA's Hubble Space Telescope and Gemini Observatory.
Measuring the speed of the stars swirling near the cluster's center with the Gemini Observatory, the astronomers found that the stars closer to the core are moving faster than the stars farther away.
The measurement implies that some unseen matter at the core is tugging on stars near it. By comparing these results with standard models, the astronomers determined that the most likely cause is the gravitational pull of a massive, dense object. They also used models to calculate the black hole's mass.
Credits:
This is a NASA/Spitzer image