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Guru
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Spinning Black Hole Pushes Limit

11/17/2006 10:55 PM

A Center for Astrophysics-led team has measured a black hole spinning so rapidly that it pushes the predicted speed limit for black hole rotation. It is turning at more than 57 thousand RPM, according to a SpaceDaily article.

The maximum RPM is determined by the mass of the black hole, calculated using the Kerr limit. The Kerr metric is an exact solution to Einstein's field equations and spinning black holes are also known as Kerr black holes.

Artwork Credit: David A. Aguilar (CfA). It depicts an accretion disc around a Kerr black hole. The white band near the center is where the matter to be eaten by the black hole emits vast amounts of energy in the X-ray band.

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#1

Re: Spinning Black Hole Pushes Limit

11/18/2006 2:38 AM

Jorrie is this possibly another reason the outer rotational curves of the galaxies are much faster then the outer baryonic mass should allow for? I realize the Halos have an extraordinary amount of mass, mostly mass we can't see or measure. But these black holes of a million to a billion Suns in mass/energy or gravitational field are throwing a lot of weight around so to speak and then rotating at 57,000 RPM has to cause significant disturbances within galaxies. With this magnitude of mass and rotational speed no wonder there are lots of spiral galaxies.

I recently read that the Great Spiral Andromeda M31 our sister galaxy is estimated to have a trillion stars and is 220,000 light years in diameter. This galaxy being our closest sister (not the large and small Magellanic clouds) should be the subject of a host of study programs. Right!

The immense nature of all of this is just mind blogging. 250 Billion Plus galaxies estimated from Hubble wide field observations. This is a BIG space and it's even bigger then we can observe with Hubble or the new James Webb Telescope. I hope I live long enough to see proof of dark matter and a reasonable explanation for dark energy.

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Guru
Engineering Fields - Aerospace Engineering - Retired South Africa - Member - The Rainbow-nation Engineering Fields - Engineering Physics - Relativity & Cosmology Popular Science - Cosmology - The Big Picture!

Join Date: May 2006
Location: 34.02S, 22.82E
Posts: 3817
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#2
In reply to #1

Re: Spinning Black Hole Pushes Limit

11/18/2006 3:31 AM

Guest asked: "... is this possibly another reason the outer rotational curves of the galaxies are much faster then the outer baryonic mass should allow for?"

I doubt it that there is a connection. Black holes are baryonic, so they are 'ordinary dark matter', not of the mysterious (CDM) variety that is thought to exist everywhere, including in the halos.

Further, I do not think spinning individual black holes have much influence on galaxies. The dragging around of space-time diminishes very rapidly with distance. At a distance, the gravitational effect is the same as for a non-rotating black hole with the same total energy (the non-rotating hole needs a little more matter than the rotating one to compensate for the rotational energy).

"I hope I live long enough to see proof of dark matter and a reasonable explanation for dark energy." Ditto!

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