Can we identify black holes in our path flying between the stars?
When traveling at fast speeds through the galaxy, would it be possible to identify where all the black holes were on your path? I know most black holes are identified by their affect on other nearby objects. But what would happen if it was all by its lonesome?
Would we be able to 'sense' it somehow before getting to close to be adversely affected by it? Or would we fly by, maybe getting close enough for it to deflects our course? And how much could it deflect a course (assuming you stay out of the event horizon)? Would it warping of space allow for Alcubierre drive like properties?
I guess I'd hate to get thrown into a sun because of a course alteration from a black hole, though getting caught in the event horizon wouldn't be much better. Can we detect these masses to avoid them at distance or do we need to take first trips much slower so we can scan for these anomalies and mark them for safe 'shipping lanes'?
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Another idea: Black holes shadow the cosmic microwave background. This might be used to detect them. Given that with high speeds, the microwave background in movement direction (that's the direction that's relevant if you want to avoid them) will be at higher frequencies due to the Doppler effect, I can imagine detecting them by their shadowing would be simplified.
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Barring the presence of an accretion disk surrounding these black holes - unlikely, in the absence of a compansion object - our best bet is likely to exploit gravitational lensing, the bending of light from distant objects by a massive object in front of the source. Typically, the massive object is a foreground galaxy, a massive star, or - in this case - a black hole.
The angle of the light bent can be calculated as $$\theta=\frac{4GM}{rc^2}$$ where $M$ is the mass of the black hole and $r$ is the closest distance a light ray passes from the black hole. For stellar-mass black holes (on the order of a few dozen solar masses), $\theta$ is likely going to be small because the angle is only linearly dependent on mass. When we reach masses of $\sim10^4M_{\odot}$, lensing seems more easily detectable, but at that point, we're talking about intermediate-mass black holes, which should have strong effects on the kinematics of their surroundings.
We have yet to detect lensing from an isolated, low-mass black hole, but it's not out of the question. If we did see it, it might look like this:
Image credit: Wikipedia user Urbane Legend, CC BY-SA 3.0
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