Small Black Holes: Cloudy With a Chance of Better Visibility

Rambo Tribble writes "As reported by the BBC, astronomers are hoping to reap a black-hole-hunting windfall when a giant gas cloud passes through an area within our galaxy thought to contain numerous small black holes (abstract). When the cloud interacts with the black holes, the resultant emission of X-rays should allow scientists to finally confirm their existence. 'The idea is that as the cloud speeds past these small black holes — some slightly more massive than our Sun but just a few tens of km across — gas will spiral around them faster and faster, heating up to millions of degrees and emitting X-ray light. It is a bit like allowing a giant sink to empty through thousands of tiny drains and looking for any evidence of swirling water.'"

Re:How long for the cloud to travel 1 light year?

[Anonymous Coward]

I would assume that these black holes are still on the scale of light years apart, and this cloud stretches across an area a few times the orbit of pluto. Something doesn't add up.

The area around the central black hole [wikipedia.org] is very crowded.

The black hole itself is probably about the "size" of the solar system (an event horizon a few light-hours in radius), there are multiple stars within light-weeks of the black hole itself, with orbital periods measured in years/decades, and some of them (S2, S14) come within several light-hours of the black hole, at velocities (relative to the black hole) of thousands of kilometers per second.

Any imaginary probe or lifeform magically teleported into the neighborhood would have one hell of a view in the moments before the radiation fried it to a crisp.