I was tracking these runaway stars for a SF story i had in mind, but this is the closest one i have heard of yet, and the ArXiv paper describes one that also passed thru 2.5 mya.
Gliese 710 will pass the Sun even closer
Close approach parameters recalculated based on the first Gaia data release
http://www.aanda.org/articles/aa/abs/2016/11/aa29835-16/aa29835-16.html
Close encounters of the stellar kind
https://arxiv.org/abs/1412.3648
tl:dr article
http://www.businessinsider.com/star-hurting-towards-solar-system-2016-12\
"Gliese 710 is about half the size of our sun, and it is set to reach Earth in 1.35 million years, according to a paper published in the journal Astronomy & Astrophysics in November.
And when it arrives, the star could end up a mere 77 light-days away from Earth — one light-day being the equivalent of how far light travels in one day, which is about 26 billion kilometers, the researchers worked out.
As far as we know, Gliese 710 isn't set to collide directly with Earth, but it wil be passing through the Oort Cloud, a shell of trillions of icy objects at the furthest reaches of our solar system. "
Seems like a great opportunity to send out some interstellar probes. The star will be trailing lots of ISM, free gas that would help bring a ramjet up to speed, and track till you could curve towards another destination. Likewise, a solar sail probe launched out in front of it by laser could "hitchhike" , and get some deep space ISM , and EM measurements.
Can we think of some other opportunities that this might present ? If we are past the filter by then, then we will already prob have samples of the Oort objects, but looks like they will be delivering then...
yes, i have no idea how a 25 my old star and disk could have rocks in-falling at that speed, seems like even a gas giant wouldn't do that, as Jupiter only gives you 30kps,(outside Roche limit).
Still, if Planet 9 is real, and starts slinging stuff around out there, there may be some un-bound bodies in the system soon enough....
You get infall at speeds like that by falling close to the star - it is the strongest gravitational field in the system and the closer an orbit takes you to it the faster you go. Something falling from the Oort cloud to the surface of the sun reaches a speed of 600 km/s at the moment of impact, and at four solar radii away it is moving 300 km/s. Speed goes down with the square root of distance. Sungrazing comets do this all the time in our solar system, but they are for the most part smallish. The data seeing cometary material moving across the face of... (read more)