[ExI] First Picture of a Black Hole!

[John Clark]

On Wed, Apr 10, 2019 at 9:54 AM <spike at rainier66.com> wrote:

> COOL!
>
> I am amazed that it is asymmetric and the thermal spectrum is so
> non-uniform.
>

It looks asymmetric because the matter in the accretion disk is moving very
close to the speed of light and as it orbits some of it is going toward us
and some is going away so one side looks brighter than the other. The inner
edge of the bright part comes from the photosphere, the last place
where light can stably orbit and has a radius of 1.5 times
the Schwarzschild event horizon, however because gravity is so strong we
are able  to see the back side of the Black Hole too so it works out that
the dark part in the center of the picture is 2.6 times the radius of the
event horizon. To the limits of measurement it looks exactly how Einstein
said it should, it would have been even more exciting if it didn't.

I assume they chose to image M87 instead of the Black Hole in the center of
our own galaxy because it is about 1000 times more massive.

 John K Clark
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