Regarding the question in your last paragraph: I believe it comes down to the velocity being so great relative to the solar system’s gravity well. See the “hype

Regarding the question in your last paragraph: I believe it comes down to the velocity being so great relative to the solar system’s gravity well. See the “hyperbolic orbit” phrase in this entry: https://en.wikipedia.org/wiki/A/2017_U1 https://en.wikipedia.org/wiki/A/2017_U1