Talk:GRS 1915+105

heaviest?
Can GRS 1915+105 really be claimed as the "the heaviest of the stellar black holes so far known in the Milky Way Galaxy"?

SRG A* is likely to be the most massive blackhole in the Milky Way, but can we prove this and what classifies as a stellar black hole?

- Anthony Rushton (talk) 15:41, 17 October 2008 (UTC)


 * The mass of the galactic center black hole, Srg A*, has been measured to be about 3.5×106 solar masses, far beyond the ~100 solar mass limit for a star. It is also clearly an AGN, though lately inactive.  On both these counts it seems to be excluded from the stellar black hole category, although it and all AGN likely were originally born as stellar-mass BHs that later grew by accretion and coalescence. Wwheaton (talk) 20:31, 17 October 2008 (UTC)


 * GRS1915+105 isn't the heaviest BH in the Milky way, e.g. Cygnus X-1 is ~2 times heavier (see e.g. here). Sgr A* is indeed a supermassive Black Hole, not a stellar-mass Black Hole. Sgr A* is also not an AGN (although it probably was in the past). — Preceding unsigned comment added by 130.190.107.226 (talk • contribs) 6 December 2022 (UTC)

Rotation 1150 times per second?
Please correct me if I'm wrong, but how can a black hole have a finite rotation frequency? I always understood that all the mass is in a singularity (infinitely small), which will therefore rotate infinitely fast (and thus have a finite angular momentum, which is conserved). Rotation can in my understanding only be measured at a distance, but at the event horizon there is nothing that really moves, it's only the gravity field directed towards the center of the black hole. Can anyone explain this? EmilTyf (talk) 00:11, 30 April 2009 (UTC)
 * Good question! It would probably have to be something like the period of the last stable orbit (which depends on the hole's angular momentum), but I am just guessing.  Let's watch for an expert opinion.  Wwheaton (talk) 22:16, 30 April 2009 (UTC)
 * The 1,150 times/sec is wrong. Also it is quoted from a dead link, which is never great.  1,150 is the maximum possible spin rate for a black hole of this type.  GRS 1915+105 is thought to be spinning near, but not right at, the maximum rate.  In 2006, it was calculated to spin at between 82% and 100% of the maximum rate.  This has since been refined to be somewhere very close to 0.98 times the maximum spin rate.  Of course black holes don't really have a spin rate, but they do have mass, angular momentum, and an event horizon with a finite size.  Their "spin" is usually represented by a dimensionless value a, which is a fraction of the maximum possible spin for that black hole.  As a spinning black hole approaches the maximum possible spin, its event horizon shrinks towards the singularity and the tangential velocity at the even horizon approaches the speed of light.  Neither of these limits can actually be reached, although it appears that a majority of stellar black holes approach it. Lithopsian (talk) 21:28, 25 November 2017 (UTC)

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meaning of its denomination
The first paragraph goes like: ...and "105" is declination in units of 0.1 degree (i.e. its declination is 10.5 degrees).

But that's obviously wrong. The declination of GRS 1915+105 is +10° 56' 44". This reads 10 degrees 56 minutes (of arc) and 44 seconds (of arc), which is approximately 10+56/60 = 10.9 degrees. --223.73.196.77 (talk) 09:19, 12 February 2017 (UTC)
 * ✅ Thanks! Gap9551 (talk) 17:32, 12 February 2017 (UTC)

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