

NASA live streaming announcement on black hole observations [video] - uvdiv
http://www.nasa.gov/news/media/newsaudio/index.html

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uvdiv
Some briefing materials are already up,

[http://www.nasa.gov/mission_pages/nustar/news/telecon2013022...](http://www.nasa.gov/mission_pages/nustar/news/telecon20130227.html)

Spoiler: it's the first measurement of a black hole spin.

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StevenRayOrr
Not having the necessary background in physics, I'm not quite sure what this
means. I'm sure some pop-science site will break it down later, but is the
gist that this has implications on our understanding of the way that black
holes expand?

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Tloewald
I don't think so. Theory of black hole formation predicts they will spin
(although emitting energy slows the spin). They have different predictions for
the kind of spin or lack thereof which would produce different observations --
and the data gathered supports one spinning model over another, either of
which agrees with theory. Non spinning black holes would be perplexing.

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jlgreco
What does it mean for a black hole to spin? Does that mean that matter past
the event horizon is in motion, and information about that is somehow being
leaked out? Or just that matter outside the event horizon is circling the
drain?

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Udo
Matter past the event horizon falls into the singularity pretty quickly, and
that's a mere dimensionless point in space. But the singularity's spin does
have an effect on spacetime around the black hole, in effect creating a second
(much stranger) type of event horizon called an ergosphere. In a way one could
say that rotation changes the shape of the black hole and that property can be
observed from the outside to determine the spin. This is cool because, while
pretty much everybody was certain that black holes _do_ spin, this hypothesis
was not yet backed up by data. The phenomenon doesn't have anything to do with
quantum information leaking out, however.

I didn't get to see the actual announcement but my guess is that effect of the
spin on spacetime has now been actually observed in the wild.

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malkia
I just missed it.

Is there a recording of it? Never figured out how to get it out of ustream...

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DavidBradbury
Full text new release:

[http://www.nasa.gov/home/hqnews/2013/feb/HQ_13-063_NuSTAR_Bl...](http://www.nasa.gov/home/hqnews/2013/feb/HQ_13-063_NuSTAR_Black_Hole_Spin.html)

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jmeekr
Feel like I'm listening in to an old school radio broadcast.

