Spinning Black Hole's Edge Rotates At Nearly the Speed of Light 227
astroengine writes "Astronomers have directly measured the spin of a black hole for the first time by detecting the mind-bending relativistic effects that warp space-time at the very edge of its event horizon. By monitoring X-ray emissions from iron ions (iron atoms with some electrons missing) trapped in the black hole's accretion disk, the rapidly-rotating inner edge of the disk of hot material has provided direct information about how fast the black hole is spinning. Astronomers used NASA's Nuclear Spectroscopic Telescope Array (NuSTAR) — that was launched into Earth orbit in June 2012 — and the European observatory XMM-Newton measured X-ray radiation as a tool to directly infer the spin of NGC 1365's black hole. 'What excites me is the fact that we are able to do this for the very massive black holes at the centers of galaxies but we can also make the same measurement for black holes in our galaxy ... black holes that resulted from the explosion of a star ... The fact we can extend this from billions of solar masses to 10 solar masses is pretty cool,' Fiona Harrison, professor of physics and astronomy at the California Institute of Technology, Pasadena, Calif., and principal investigator of the NuSTAR mission, told Discovery News."
Re:My thought... (Score:5, Insightful)
You might as well say it's because they are made of rainbows and ponies unless you have math to support your theory.
Seems obvious to a naive engineer! (Score:5, Insightful)
Re:Is the hole rotating, or just the disk? (Score:5, Insightful)
By monitoring X-ray emissions from iron ions (iron atoms with some electrons missing) trapped in the black hole's accretion disk, the rapidly-rotating inner edge of the disk of hot material has provided direct information about how fast the black hole is spinning.
So the summary indicates that measuring the accretion disk somehow tells them exactly how fast the non-emitting portion is spinning.
The useful answer is in the link from the above quote:
Risaliti and his colleagues measured X-rays from the center of NGC 1365 to determine where the inner edge of the accretion disk was located. This Innermost Stable Circular Orbit - the disk's point of no return - depends on the black hole's spin. Since a spinning black hole distorts space, the disk material can get closer to the black hole before being sucked in.
So they calculated the spin of the black hole by comparing the observed orbit to the calculated orbits possible from the calculated mass based on observable gravitic effect on nearby objects. Yes, there's uncertainty there, but until someone discovers a new detail in astronomy, that's as accurate as we can get.
Re:know your audience (Score:5, Insightful)
i love how this summary explains what an ion is, but assumes i know the definitions of black hole, x-ray, and solar mass. great writing, folks!
You forgot "space-time", "event horizon" and "accretion disk".
I'm also astounded by the discovery of black holes resulting from an explosion of a star. So far I thought that a black hole is a result of an implosion of a star. This is a major new discovery!
Re:know your audience (Score:5, Insightful)
That's the point. It wastes a bunch of words explaining what an ion is.
If you don't know what an ion is the rest of the words are going to make any sense anyway.
Re:know your audience (Score:4, Insightful)
I think everyone sort of knows what a black hole is by now; who hasn't had an x-ray? and mass is just high school chemistry, if not junior high.
Ions are elementary chemistry as well, and are covered early on in school, grade 7 or 8 at the latest I think. Acids and bases, potato batteries, etc.
And knowing what an "x-ray exam" is doesn't tell you anything about what an x-ray actually is, nor what they are doing near black holes.
Re:Seems obvious to a naive engineer! (Score:4, Insightful)
Light doesn't have a rest mass, but it most certainly has momentum. Perhaps you need to review what E=MC^2 means, Light is affected by gravity as witnessed numerous times in astonomy. Perhaps your "ARGGG!!!" should be directed at yourself.