[ordu]

> A micro black hole (e.g. Earth mass) passing through the solar systems would likely go undetected unless it collides with something (which is improbable).

Solar wind? Would it generate some interesting effects when coming too close to a black hole? All these protons accelerated to a near light speed, probably hitting each other and running away into a black hole.

[The_Colonel]

An Earth-mass black hole will have a similar gravitational effect on solar winds as Earth. Can we detect these effects on solar winds from distance? Maybe if we watch for them in that particular direction of empty space, but will we? The effects would be localized and short-lived at each particular place on the trajectory.