Omega Centauri Black Hole

[astroron]

Possible Black Hole in OMEGA CENTAURI, image from Hubble Space Telescope.
This is the text from the image that is posted on the Hubble Heritage web site.
Ron


STARRY SPLENDOR IN CORE OF OMEGA CENTAURI

The core of the spectacular globular cluster Omega Centauri glitters with the combined light of 2 million stars. The entire cluster contains 10 million stars, and is among the biggest and most massive of some 200 globular clusters orbiting the Milky Way Galaxy. Omega Centauri lies 17,000 light-years from Earth.

Astronomers Eva Noyola, of the Max-Planck Institute of Extraterrestrial Physics in Garching, Germany, and Karl Gebhardt of the University of Texas at Austin, have reported on the possible detection of an intermediate-mass black hole in the core of Omega Centauri.

The result is primarily based on spectroscopic measurements obtained with the Gemini South observatory in Chile which suggest the stars are moving around the central core of the cluster at higher than expected velocities.

Among the possible explanations for these speedy stars—and the one favored by their study—is that an intermediate-mass black hole of approximately 40,000 solar masses resides at the center of Omega Centauri. Its powerful gravitational field speeds up the motions of stars near the core.

Astronomers have speculated for years that some globular clusters may harbor in their centers medium-size, or intermediate-mass, black holes with masses of some tens of thousands of suns. Medium-size black holes are much less massive than the supermassive black holes, which are up to billions of solar masses and reside in the centers of large galaxies.

Hubble images taken with the Advanced Camera for Surveys were used in key areas in support of this study: to help pinpoint the center of the cluster, as well as to measure the amount of starlight at the cluster center.

Using the European Southern Observatory’s Very Large Telescope in Paranal, Chile, Noyola and Gebhardt are planning to obtain follow-up observations to help confirm the existence of an intermediate-mass black hole.

The Hubble images were taken in June 2002.

Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA)
Acknowledgment: A. Cool (San Francisco State University) and J. Anderson (STScI)



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[dannat]

so it's possibly a giant sink with the stars flowing in -
the only important thing is whether they are going in clockwise or anti/c -

[Paddy]

Thanks for the post - very interesting. I must say I often wonder about this when I'm looking at this GC in particular - so many stars!

[MikeyB]

The Hubble Heritage Project (http://heritage.stsci.edu/index.html)

[skwinty]

I often wonder how many stars, of the millions gravitating around this black hole, have already been devoured. Could be a lot more than we imagine!
Oh, for answers to these questions.......:(

[AlexN]

good pickup ron. Thanks for the info!

[glenc]

Thanks Ron, is omega Cen a GC or a mini galaxy? ;)

[Argonavis]

Glen

define mini -galaxy

It is known that with galaxies that have been studied and measured that the central black hole comprises 0.2% of the total mass of the central bulge. With a 40,000 solar mass SMBH at the centre of Omega, then if Omega was a galaxy obeying this rule it would have 20 million solar masses. Most estimates of the total mass of Omega give it between 5 and 10 million solar masses.

So unless mini-galaxies do not obey this rule, then Omage is not a mini-galaxy.

With GC's, the age histogram overlaps with OC's, so the disctinction is blurred at the edges. Most galaxies contain stars of all ages, some have lots of gas and dust, other virtually none. Galaxies also come in all sorts of morphologies, so the definition of a galaxy is fairly broad.

Most likely mini-galaxies (like this: http://www.abc.net.au/science/news/stories/s101107.htm) are really just star clusters that have been dissassociated with their parent galaxy through mergers and tidal interactions.

Quoting from the article: "..Star clusters generally contain up to a million stars, while galaxies contain closer to a billion. Our own galaxy, the Milky Way, contains 10 billion stars, and already 100 billion galaxies have been identified.

Galaxies also differ from clusters in that they may contain dark matter - the mass of a formation gives away whether or not dark matter is present..."

Note the error by a factor of 10 (or more) in the number of stars attributed to the Milky Way.

I have read of some evidence of intergalactic field stars which would have got where they are via this process. Maybe this will be the Sun's fate after the Milky Way's encounter with Andromeda.

[glenc]

Thanks Will.

[renormalised]

We now think omega Centauri is the core region of a small galaxy that had been previously ripped apart by the Galaxy. Being small, it never had the initial central core mass to form a large, supermassive black hole. More than likely, the hole formed from the collision of stars and gas/dust clouds in its central regions during its formation. If it's as large as they say, 40000Ms, then probably upto 200,000 - 400,000 stars could've been involved in its formation (discounting gas/dust and taking the majority of the stars as being M class dwarfs).