Just a moment...

The article gets interesting half way down the page when it talks about the ngEHT project - and the confirmations of theory they expect it to reveal.

CfA’s Michael Johnson "is leading a mission proposal called Black Hole Explorer that he aims to submit to NASA in 2025. To be launched in 10 years into geosynchronous orbit, the spacecraft’s 4-meter dish would expand the baseline of ngEHT to about 35,000 kilometers, enough to see the photon rings."

spoiler:

"Theory predicts multiple, nested photon rings, and the size and shape of the innermost one would help pinpoint the black hole’s mass, spin, and even the inclination of its swirling disk. By imaging multiple black holes with different life histories, researchers could find out how their spins are affected by mergers or a sudden feast of surrounding material.

The ngEHT and its orbiting outrigger should also be able to test Albert Einstein’s theory of gravity, general relativity, in the most extreme conditions ever, Doeleman says. “[It will] bring us as close to the edge of a black hole event horizon as we are likely to be for many years to come."