Thread by @skdh

Tomorrow (April 10) at 3pm CEST (9am Eastern Time) the first results from the Event Horizon Telescope (EHT) will be announced:

eso.org/public/announc…

What to expect? /begin thread

(Image: Screenshot from this video: )

The scientific mission of the Event Horizon Telescope is to capture an image of a black hole horizon. So far, we have indirect evidence for the existence of a black hole horizon, but have not actually “seen” one. 1/

You cannot really “see” a black hole, but you can see the way that a black hole wraps light around its horizon. It is a very strong lensing effect, not entirely unlike to the warped lensing that you can create with some photo apps. (Image: Artist's Impression of black hole) 2/

The Event Horizon Telescope has been looking at two supermassive black holes, that is Sagittarius A* in the Milky Way (about 26,000 light years away) and the black hole in M87 (about 50 million light years away). 3/

The black hole in M87 is about a thousand times farther away, but is also a thousand times larger than the one in our own galaxy, so they appear at almost the same size in the sky. 4/

I am guessing (rumor alert!) that the first results from the Event Horizon Telescopes will be for M87, not Sagittarius A* because the most recent Sag A* measurements were not of good quality and have to be redone. 5/

The Event Horizon Telescope is not one telescope, but a global network of 8 telescopes (in green in the image), with a total collaboration of about 250 scientists. Image Credit: ESO/O. Furtak. Image Source: eso.org/public/images/… 6/

Using these different telescopes together makes it possible to resolve much smaller structures than any one separately could do. 7/

The Event Horizon Telescopes measures light in the radio regime, ie in a regime that we cannot see by eye. This means that the color of the image will be chosen for visual purposes and not be an actual color. 8/

A simulation of what the results might look like is in the image below (right).

Image credits: Andrew Chael
Image source: blogs.discovermagazine.com/d-brief/2019/0… 9/

What do physicists hope to learn from this measurement? The EHT monitors what happens very close by black hole horizons. To begin with, this is an opportunity to test whether Einstein’s theory of general relativity describes black holes correctly. 10/

Besides this, the EHT results help physicists learn more about the way that matter swirls around black holes and creates “jets”, that are directed beams of highly energetic particles. 11/

Supermassive black holes play a central role in galaxy formation. Learning more about how they affect matter in their environment therefore helps us understand why the universe is the way it is. 12/

Maybe most of all, the EHT measurements will lay to rest any remaining doubt about the existence of black holes, honoring the old adage “Seeing is believing.” /end thread