On Monday, April 15, 2019 at 4:57:15 AM UTC+3, Hans Aberg wrote:
On 2019-04-12 19:03, Tom Roberts wrote:
The picture from the Event Horizon Telescope:
https://apod.nasa.gov/apod/ap190411.html

Why is the center black?
Does the accretion disk just happen to be in a plane normal to our
line-of-sight?

(The near-perfect circularity of the image implies this
may be so, but the varying intensity implies not.)

In particular, if the accretion disk is not in a plane normal to our
line-of-sight, why don't we see light from the portion of it between us
and the black hole? And why isn't the image elliptical?

There is a good explanation of the expected image at [1], incidentally
published before the black hole image. In short, relativistic effects
cause the image.

1. https://www.youtube.com/watch?v=zUyH3XhpLTo

I notice possible one reference about above link ?

Luminet Jean-Pierre, 1999.
Black Holes.
Cambridge University Press, (1992), reprint 1999.
pages 137-146 (10. Illuminations).

Best Regards,

Hannu Poropudas