IP: Spinning Black Hole

[David Farber <dave () farber net>]

> From: "PAUL JULIEN" <p.julien () worldnet att net>
> To: <farber () cis upenn edu>
> Subject: Spinning Black Hole
> Date: Thu, 10 May 2001 18:03:54 -0400
> X-Mailer: Microsoft Outlook Express 5.00.2615.200
>
> Dave:
>
> Evidence for a black hole spinning at 450 Hz.  APS = American Physical
> Society.
> Nice graphics and explanation on the link
>
> http://www.gsfc.nasa.gov/GSFC/SpaceSci/structure/spinningbh/spinningbhpix.ht
> m  ,
>
> the link given in the text.  You have to try to imagine an object about the
> size of Long Island, but with a mass of about 2 millions earths, spinning at
> 450 revolutions/sec.   And this is a "micro-blackhole", not a big one.
>
> Paul Julien
> Rutherford NJ
>
> *
>
>
> PHYSICS NEWS UPDATE
> The American Institute of Physics Bulletin of Physics News
> Number 538  May 7, 2001   by Phillip F. Schewe, Ben Stein, and
> James Riordon
>
> THE FIRST DIRECT EVIDENCE OF BLACK HOLE
> ROTATION arrives in the form of the telltale dimming of x rays
> coming from a microquasar about 10,000 light years from Earth.
> The object in question, GRO J1655-40, consists of a black hole
> devouring a nearby normal-star companion.  The pillage is not
> direct.  Instead matter from the star collects on an accretion disk
> orbiting the black hole before taking the final plunge through the
> event horizon.  This jumping-off platform is so hot that matter there
> glows at x-ray wavelengths.  Seeing this glow and measuring how
> the glow changes over short time intervals requires the use of a
> special telescope the Rossi X Ray Timing Explorer (RXTE), which
> takes snapshots at a rate of 1000 per second.  A common type of x-
> ray modulation seen in x-ray binary systems, called a quasi-periodic
> oscillation (QPO), is thought to occur because the hottest x-ray
> emitting part of the disk, in its swift orbit around the black hole, is
> periodically occluded by the black hole itself.  The gravitational
> fields at work are enormous after all, the inner edge of the
> accretion disk is only tens of kilometers or so  from a black hole of
> about 7 solar masses.  The specific orbital radius can be deduced
> from the laws of general relativity which predict a fixed "innermost
> stable orbit" for matter circling a black hole.  In this case the
> predicted orbit is about 64 km.  Many theorists believe, however,
> that a black hole that spins would have a much smaller event
> horizon and this would permit orbiting matter to attain a much
> tighter innermost stable position, and a correspondingly faster
> orbital rate.  At last week's APS meeting in Washington DC, Tod
> Strohmayer of the Goddard Space Flight Center (301-286-1256)
> reported a previously undiscovered QPO pattern in x rays from
> GRO J16550-40. The frequency of this QPO, 450 Hz, is the highest
> ever seen for x rays coming from a black hole system, implying an
> orbital radius of only 49 km a value consistent, Strohmayer says,
> with a spinning black hole.  (Preprint on Los Alamos server: astro-
> ph/0104487);video at
> http://www.gsfc.nasa.gov/GSFC/SpaceSci/structure/spinningbh/spinningbhpix.ht
> m



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