sdoeleman

A running joke among BH researchers is that we need to send one of us with a laser pointer to the event horizon and then point the laser back to earth. That would give us a lot of info, but also cost us an astronomer (good value?). The EHT will get us closer to the BH and Event Horizon than we have ever been, and in addition to a possible image, we can also trace orbits of material in time, so there are a number of cool experiments that will play out over the next 3-5 years. A lot to keep us occupied, so the ceiling is some ways away!

This is a very interesting question, and it's true that if a black hole ingested only particles of one charge it could accumulate charge and then repel like charges, but what may happen in reality is that protons or positrons would be attracted to the charged BH and cancel the charge. In other words, BH's are always expected to be neutral.

The beauty of the EHT is that we really don't know exactly what we'll see. If we understand the physics and General Relativity, then we can predict what we'll see: a bright ring near the last orbit photons can trace with a dim interior (caused by gravity pulling ferociously on escaping photons coming toward us). Einstein's theory predicts what we should see, but if we see something else (a warped shadow or a completely unexpected shape) then things get very interesting.

The EHT has already measured the size of the supermassive BH at the center of the Milky Way (and also another at the heart of the Virgo galaxy). Each year we add more telescopes to the global array, filling in the earth-sized 'lens', so our ability to image gets better all the time. In 2017, we'll add ALMA, a huge facility in Chile, and that will enable a really good shot at bringing a BH into focus for the first time.

Wow! Someone is thinking BIG! We could certainly put a station on the Moon and the resulting magnification factor would be huge - 80,000 times better than Hubble (check me on that). The problem is that this might be too good in that we probably would not have the sensitivity (unless the antenna on the moon was very large) to detect a black hole on such a long baseline. The reason is that there has to be a lot of brightness on very small scales. Also, we'd have to wait a long time before the Moon data could get back to us! We hope to image other galaxies with the EHT - astronomers want to image the high speed jets launched by black holes and those show up in a number of sources. THe EHT will provide the sharpest view of these as well.