 Let's take a look at some of the stars in our neighborhood, out to around 25 light-years. That's about as far as stellar parallax measurements from ground-based telescopes can take us. Proxima Centauri is a dim-red star. It is the nearest known star to the Sun, and thought to be a third member of the Alpha Centauri system. Its average luminosity is very low, and it is quite small compared to other stars, at only about one-eighth the mass of the Sun. Astronomers predict that this star will remain for another four trillion years, a thousand times longer than our Sun. Alpha Centauri A and B form a close binary system that is separated, on average, by a distance slightly greater than the distance between Uranus and the Sun. A, the main star, is bright and yellowish. B is not quite as bright, and has an orange tinge.