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Fastest Spinning Black Hole Ever Found
brian0918 writes, "NewScientist reports that researchers in Cambridge have detected a black hole spinning at nearly 1,000 times per second — the fastest ever recorded. From the article: 'McClintock's team examined a black hole in our galaxy called GRS 1915+105, which lies about 36,000 light years away. They found the innermost stable orbit around GRS 1915 is so close that the black hole must be spinning at nearly 1000 times per second. The finding supports the idea that only fast-spinning stars can collapse to create powerful explosions called long gamma-ray bursts.'" The Astrophysical Journal abstract is open but you have to be a subscriber to read the full article there.
The original article is from The Astrophysical Journal and I'm not sure if you can read this but I'll link it here. I have an account so that may be unreachable, if it is try the PDF of it or the abstract. I often enjoy reading the original article no matter how large and complex it is. If anything, it causes me to look up more terms so that I feel like I'm learning something.
My work here is dung.
If there was a planet with a gravitational pull equivalent to a Black Hole, I bet they'd find it pretty quick.
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The astrophysics arXiv preprint from June.
because they don't use light to detect either, they use the effect on nearby matter; which means their gravity, and not their size/light is what matters. Although someone mentioned that black holes also have a kind of "halo", which could also still be used. Also there is an accretion disk (I believe that's what it's called), around a black hole where stuff is getting sucked in. That would create a large and visible effect.
Nonetheless, a planet will make a star vibrate ever-so-slightly-and-slowly, whereas a black whole will make who masses of stuff rotate around it, and suck them in.
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If you'd like to see the whole article, as published in the Astrophysical Journal, you can find it on the astro-ph journal pre-print server. It's not the "official" journal version, but it should be identical to it (and was submitted to the preprint server by the authors).
I couldn't tell if you were experimenting with poor-man's cryogenics or looking for the orange sherbet.
Here's a 20 mile diameter pulsar spinning at 716 Hertz. When you factor in the increase in rotational speed with the black hole contraction, 1K sounds real plausible.
No folly is more costly than the folly of intolerant idealism. - Winston Churchill
Not that kind of Black Hole, you idiot!
http://en.wikipedia.org/wiki/Gamma_Ray_(band)
The black hole doesn't actually squish. The event horizon contracts due to frame dragging.
I'm not certain, but you might be thinking about frame dragging. Rotating objects drag space-time around with them; the more massive the object, the stronger the effect. Because black holes tend to the massive side and can spin very very fast the frame dragging effect can be very strong near the event horizon.
:-)
Because of this effect, it is impossible not to orbit a rapidly spinning black hole as you fall in; you'll get dragged around along with space-time. I'm guessing (without having actually heard or read this) that you may only get centrifugal force for your angular velocity that exceeds the speed at which space-time is rotating. Otherwise, as far as space-time is concerned, you're just falling straight in. The end effect of this is that objects that appear to be rotating around the black hole to a distant observer may actually be falling straight in.
I've probably put enough conjecture and botched explainations in there to attract the attention of a real physicist, so just hang on for the real explanation.
I have suffered from being misunderstood, but I would have suffered a hell of a lot more if I had been understood.
That is true. However, this is currently our best estimate, and the theory applied is pretty well-respected. It may be interesting to know that this finding supports a 1997 suggestion that this particular black hole spins very close to its maximum. The 1997 paper attempted to explain in theory the x-ray jets this black hole emits by suggesting it spins. In contrast, this new paper actually documents an attempt to measure the spin.
Anyway, assuming the theory is correct, their method sounds pretty plausible to me (also assuming I'm understanding the paper and article right).
Basically, the size of a black hole event horizon depends mainly on its mass. However, if the black hole is spinning (most or all are believed to due to conservation of momentum), the event horizon contracts due to frame dragging.
Of course, we can't directly see the event horizon to measure it like we can measure the sun's radius. These black holes are far too distant to resolve. But, matter falling into the black hole is heated up due to friction. Just before it passes the event horizon, it gets so hot it emits x-rays that are detectable from earth.
The clever part is that the energy of the x-rays is correlated to the emitting particle's radius from the center of the black hole, since as particles spiral in further, they heat up more and more. So if you know the mass and can measure the highest frequency of the emissions, you can calculate the rate of spin. Of course, finding the mass and measuring those x-rays is not at all trivial, and the final step of calculating the spin probably took the 6 researchers who published the paper a year or so worth of work.