Astronomers Planning To Image Milky Way's Central Black Hole

99luftballon writes "Astronomers are planning the Event Horizon Telescope project in Arizona on Wednesday — and say in three or four years they should be able to image the ring of matter around the supermassive black hole at the center of the Milky Way. The black hole is 26,000 light years away, but should be large enough to check if Einstein got his equations right."

What If...

[mlauzon]

It turns out there is no black hole at the centre of the Milky Way?

It's not quite exactly imaging

[NixieBunny]

The telescope that they use is actually several radio telescopes capturing the same signal at the same time, in an observing mode called VLBI for Very Long Baaseline Interferometry. The data captured are correlated off-site (or in real time if they can build a trans-oceanic Gbyte/sec data link) to get a wave-by-wave signal match, producing interference fringes that permit the construction of a very high resolution image. These days, they store the GByte/sec data on a bank of hard disk drives and FedEx them to the correlator in Virginia.

I happen to work on one of these telescopes, the Heinrich Hertz Submillimeter Telescope on Mt. Graham in Arizona. We have a hydrogen maser on site to produce a clock accurate enough to collect the data synchronously with other telescopes in other parts of the world.

Re:more of a test of relativistic particle physics

[Black Parrot]

We expect that Sagittarius A* is a black hole, and the definition of black hole basically means that it has an event horizon. If, contrary to everyone's expectations, it turns out not to have an event horizon, the most likely interpretation may not actually be that GR is wrong. It may actually mean that there is something wrong with relativistic particle physics. It's possible that the process of formation that we think leads to a black hole actually stops short of forming a black hole, and instead forms some other exotic object. There are various speculations about these things: gravastars, fuzzballs, quark stars, boson stars, q-balls...

IANAPhysicist, but AIUI:

A fuzzball would be indistinguishable from a black hole, since it's a hypothesis about what's what inside the event horizon.

A gravastar may also be indistinguishable (from outside), but I'm less sure about this.

The others, I think, would still form black holes if they had the amount of mass inside the amount of volume required by the observations.

Correct me if I'm wrong; I love learning about this stuff.