As you probably know, there is a star, 60% the size of the Sun, approaching us at about 15 km per second.
It will be as near as 2 to 3 light months away in 1.3 million years. Which may be quite annoying due to comets and such.
For all those details I encourage you to Google around, or consult Wikipedia for the latest known facts about this. There is only one thing I have to say here that everyone seems to neglect. It occurred to me during the debate I had with a friend this morning:
Him: You said that it would be dangerous for our planet if some big rock were to hit our Sun. Why do you think so?
Me: If a hydrogen atom from far away free-falls on the Moon, its velocity, relative to the Moon’s surface, will be equal to the Moon’s escape velocity, which is 2.4 km/s. Its temperature would be the same as that of an average hydrogen atom on the Sun’s surface.
Him: That much?
Me: Yes. And if a hydrogen atom from far away falls onto the Earth, accelerated only by Earth’s gravity, its resulting temperature will be about 80 000 Kelvins.
Him: And if a hydrogen atom falls onto our Sun from far away, what would the atom’s temperature be?
Me: Over 100 million Kelvins. As hot as if it had just come from a thermonuclear explosion.
Him: Get out of here!
Him: A lot of hydrogen and other atoms from the Gliese 710 system may be in free fall towards our Sun as we speak, right?
Me: They are still 63 light years away and the gravity between them and our Sun is still incredibly small, but the final velocity will be over 600 km per second.
Him: It’s even a bit worse than just a free fall, isn’t it?
Me: Yes it’s even a bit worse, they have some initial velocity already. There is a small probability for a central collision of a big rock with our Sun.
Him: But this time it might be different?
Me: Yes. Imagine that a planetoid from G710 manages to fall directly into our Sun. It would be like a small Nova!