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."
Is the hole rotating, or just the disk? (Score:3, Informative)
Have they shown that the black hole is rotating near c, or just that the accretion disk is rotating near c at the event horizon? The accretion disk and the black hole are not necessarily spinning in sync. If they mean the accretion disk, then, like DUH: if it wasn't rotating near c, it would fall straight in and there wouldn't be a disk.
light is influenced by gravity (Score:5, Informative)
" Yes, light is affected by gravity, but not in its speed. General Relativity (our best guess as to how the Universe works) gives two effects of gravity on light. It can bend light (which includes effects such as gravitational lensing), and it can change the energy of light. But it changes the energy by shifting the frequency of the light (gravitational redshift) not by changing light speed. Gravity bends light by warping space so that what the light beam sees as "straight" is not straight to an outside observer. The speed of light is still constant."
Dr. Eric Christian
Re:WRONG! (Score:3, Informative)
So many people (a number of whom who should know better) get this totally wrong because you always here that a black hole has "such powerful gravity that not even light can escape!!!111!!!"
This is another failing of Science Channel styled science shows*. They neglect to tell you that light doesn't escape because the gravity well created by a black hole warps space, not because photons are pulled on by gravity. It may sound like I'm splitting hairs since the overall end result is the same but a lot of people mistake it as meaning that light is sucked in to the black hole because particles with mass are also sucked in. This also doubtlessly leaves people scratching their head over the misconception that maybe the gravity is forceful enough to actually attact the light.
* Yeah, I'm the guy who complained about definitions being used too often in another thread.
Re:Spin equal to mass? (Score:4, Informative)
No. Black holes are not dark matter. Well, I mean, yeah, they are dark. Like black dark. Like "how much more dark could they be? None, none more dark." But they are normal matter, not dark matter. The mass of (nearby) galactic core black holes is easily measured by measuring the speed of closely orbiting stars. Their velocity is entirely dependent on the mass inside their orbit, so no need to invoke dark matter.
Re:WRONG! (Score:4, Informative)
Re:Seems obvious to a naive engineer! (Score:2, Informative)
Re:know your audience (Score:3, Informative)
Re:know your audience (Score:5, Informative)
> I'm also astounded by the discovery of black holes resulting from an explosion of a star.
Really massive stars (greater that 250 solar masses -- i.e., 250 times as massive as our own Sun) most assuredly do explode, and *very* violently, leaving behind a black hole. It's believed that this is a key source for gamma ray burst events. It's also thought that many of the first stars in the universe, not long after the Big Bang, exploded this way, spewing jets of metals at relativistic speeds.
To be fair to you, it's now known that there are actually several different types of supernova. Some core collapses do occur without a big earthshattering "kaboom." The really massive stars explode due to photodisintegration, and result in a hypernova -- a ridiculously intense, you-don't-want-to-be-within-a-hundred-light-years kind of thingie. :)
http://en.wikipedia.org/wiki/Photodisintegration [wikipedia.org]
http://en.wikipedia.org/wiki/Supernova [wikipedia.org]
Re:Thought experiment (Score:3, Informative)
It would be ripped to shreds by tidal and frame dragging forces, heated to millions of degrees by frictional heating, emit some very lively photons, and the resulting plasma would become part of the accretion disc.
And this is assuming you could even get it in place without the same result befalling the construction crew, their equipment, and raw materials.
Re:WRONG! (Score:3, Informative)
In some mediums, light moves faster than it does through a vacuum.
No, it doesn't. Not only does such a material not exist, it is proven beyond any reasonable doubt to be impossible.
That depends on what exactly you mean with the "speed in the medium".
You certainly can have a phase velocity larger than c, and AFAIK you also can have a group velocity larger than c. What you cannot have is a signal velocity larger than c.
Re:Is the hole rotating, or just the disk? (Score:4, Informative)
Black holes can evaporate in a few billion years, and then their event horizon disappears. So an event horizon is not the end, just some temporary area with slow time.
A black hole of one solar mass will take 10^67 years to evaporate from Hawking Radiation -- and this time is proportional to the cube of the mass, so think about those SMBHs out there with billions of solar masses. That's a mind-bogglingly long time. You might think it's a long time waiting in line at the Department of Transportation, but that's peanuts compared to black hole evaporation...
And that's only after the CMBR has been red-shifted into near non-existence since until then the black hole is absorbing more energy than it is losing.
Though there are in theory primordial black holes (ones created in the moments after the Big Bang) that would have a lifespan measured merely in billions of years.
Re:know your audience (Score:4, Informative)
In that US region almost everyone would deny all of this, no matter of the education level. The light coming from the accretion disk of that black hole is coming here from before 6000 years ago, when the universe, earth, man, and everything else was created by the almighty god.
I'm an atheist with a college degree who works daily with salt of the earth types in the Bible Belt. In general, physics understanding is spotty around here but actual Young Earthers are extraordinarily rare (to the point where I've never actually met one). You're unlikely to find someone who can tell you the difference between weight and mass and if you want them to use a torque wrench make your specs in foot pounds instead of Newton meters. However, pictures of Jesus riding a T-Rex are taken as ridiculous jokes since, obviously, they weren't contemporaries.
Hell, the guys in the oil and gas industries make their fucking paychecks based on a fundamental understanding of geology, evolution, and the time scales involved.
You may want to question your assumptions more in the future if you would like your worldview to more accurately reflect reality.
Peter