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...
NUMBERS EDITED
I or businessinsider must be missing something with regards to the degree of danger posed by a star going through the oort cloud or with regards to it being a particularly extreme pass, what with businessinsider calling it the strongest perturbation in the future history of the solar system.
The density of stars in our local neighborhood is ~0.004 stars per cubic light year. This close approach is calculated to be ~0.21 light years (13,000 AUs, 440x the distance to Neptune). A sphere that wide has a volume of 0.04 cubic light years. Stars should be at least that close about 0.016% of the time, or for about 713,000 total years out of Earth's history.
Typical relative velocities of nearby stars are in the low tens of km/s. This one is 13.8 kilometers per second. Let's say it spends circa 0.1 LY on a 'close approach' within this volume. Thats a circa 2000 year encounter and you'd expect circa 356 encounters like this one over the solar system's history, one every 13 million years with more continuing into the future. Indeed the first paper mentions other recent approaches that are nearly as close.
Going back to first principles, if you assume a 15 km/s average encounter speed and an approach radius of 0.21 light years, you expect about ~127 encounters at least this extreme over the solar system's history, one every 36 million years or so. More frequently if the average velocity is higher or the spread of velocities is larger. You have to go down to a distance of 0.019 light years (1190 AUs, or 40x the distance to Neptune) before you're pretty sure you aren't going to get an encounter that extreme or more over the lifetime of our solar system so far. Granted one could argue there could be a bit of a selection effect.
This seems to suggest to me that stellar close approaches are likely less disturbing to inner solar systems and/or that impacts are less disturbing to biospheres than some claim. I know that the latter has some support - there are some pretty big impacts in the geological record not associated with mass extinctions, and those that are associated with mass extinctions seem to coincide with long term stressors like flood basalt eruptions.
EDIT i updated the numbers, the timescale comes to circa 10 million years not 3 million years, caught a math burp, but the point still stands. I still can't quite figure out why they're calling it so extreme.
EDIT 2 Actually read the paper. The popular press quotes them as saying this star is the "strongest disrupting encounter in the future and history of the solar system." They ACTUALLY state that the star has the biggest influence on our solar system for at least the last and the next ten million years which is the period of time they can project, not for all time. Events like this HAPPEN, with greater frequency than mass extinctions on Earth.
EDIT 3: Their units for perturbation on the oort cloud are in units of (solar masses / distance squared / velocity ). The perturbation is stronger the slower the star moves and the more massive it is. This relative velocity is on the lower slope of the curve and the mass is higher than many stars (half a solar mass - most stars are dwarfs and I believe the sun is larger than ~80% of stars) so I can see that the SIZE of the perturbation may be a bit larger than distance alone will indicate. I would need a better handle on the distribution of relative velocities and masses to get a good handle on these numbers.
On a related note, I now can't figure out how they're modeling the effects on comets...
This article points to a paper that shows destabilized comets coming in at 160 kp/s, that is way beyond anything we have seen before,...
"The team’s spectrographic analysis, using Hubble data collected from two observing runs separated by six days, detected carbon gas and silicon in the light of HD 172555 moving across the face of the star at a speed of 160 kilometers per second."
This is a young star, and disk, but still surprising pertubations.
A New Look at ‘Exocomets’
http://www.centauri-dreams.org/?p=36939