Question

During the past 4.6 billion years, what is the closest another star has gotten to the sun?

Answer 1

None so far - stars do move around a bit within the Milkyway Galaxy but as far as we know, none have come close in 4.5 billion years.

Explanation:

The universe continues to expand and so the galaxies are all moving away from each other. Stars within the galaxy do make a orbit around the centre of the galaxy once every 250 million years or so and they do this at a speed of about 500,000 miles/hr! Called a "cosmic year". Stars do move around within the galaxy, but none have come close in 4.5 billion years. And its a good thing too, as if one did it would cause enormous gravitational changes and perhaps the end of our planetary system.