Pi Andromedae

A multiple system in the constellation of Andromeda that lies almost directly southward of the Andromeda Galaxy in the skies of Earth. Based on its parallax measurement, the Pi Andromedae system lies some 549 light years from the Solar System, which helps to explain its comparatively faint visual magnitude of +4.34.

At the heart of the system is not a single star, but a close binary pair of blue dwarfs. These two stars are separated by a little over one Astronomical Unit (that is, their distance from one another is roughly comparable to that of Earth from the Sun), orbiting their common centre of gravity every 144 days.

The two inner dwarf stars are not alone in the system. It also has a third member, a small white star pursuing a much more distant orbit around the central pair. Estimates of its distance vary from about 6,500 to 7,200 AU, or some two hundred times Neptune's distance from the Sun, and at this distance the outer white star will take nearly two hundred thousand years to complete a single orbit of the central blue binary.