It turns out that a small red-orange star called Gliese 710, currently some 69 light years away, is on a collision course with the Solar System. But before anyone panics, it won't actually collide with the Sun or any major planets, and will in fact just clip the outer edge of the Sun's Oort Cloud. And all this won't happen for another 1.5 million years or so. Check out the the full article form NEW SCIENTIST.
The brushing of the Oort Cloud is actually pretty significant. For those who may not be up on such things, the Oort Cloud is an extremely disperse 'cloud' of cometary material left over from the formation of the Solar System. It extends roughly from the outer edge of the Kuiper Belt (where we find planet-sized iceballs such as Pluto, Sedna, and Eris) at some 50 AUs out to up to two light years away from the Sun.
Such a massive object passing so close to the cloud would disturb the orbits of a great many of the comets drifting out that way, inevitably send some veering toward the inner Solar System--and Earth. So its very possible that Gliese 710 could precipitate one or more extinction events during its cosmic flyby.
But an interesting possibility no one has mentioned yet is that even while Gliese 710 mucks up the Sun's Oort cloud, the Sun will also muck up Gliese 710's Oort Cloud in turn (assuming it has one, of course. From what we understand of star/solar system formation, it should have one, but we don't know for sure). In fact, chances are the Sun, being more massive and with a more powerful gravitational influence, would likely end up drawing off more comets from Gliese's Cloud than vice-versa.
This raises an interesting possibility. Other such near-misses must have happened in the past, and each time the Sun would have drawn off comets form other stars' Oort clouds. We tend to think of all the debris like asteroids and comets in our Solar System as left over junk from the formation of the sun and planets, but what if a significant percentage of it has actually been 'stolen' from other stars during near misses? It might give a boost to panspermia theories, which theorize that life on Earth originated from space and was seeded by ancient comet impacts.
Of course we can't know for sure until there's an extensive survey of the chemical composition of various comets, and that's at least decades away. But its something to think about.