So far as we know, the sun and our solar system are not in orbit around any star closer than a few light years. There are no objects large enough to provide the necessary gravitational field so that the speed of our sun would allow it to be in a bound orbit. Between the sun and Alpha Centauri, there are no dwarf stars larger than 0.05 times the mass of the sun, despite many careful searches for such objects. Meanwhile, the gravitational force between the Sun and Alpha Centauri is so weak that this nearby star could not have any effect on the sun that is greater than, say , the gravitational effect that the rest of the stars in the Milky Way have upon the Sun.