Quick! Name the widest double star in the sky. If you chose Alpha Centauri and its faint, distant companion Proxima (separation 2.2°), you would have been correct ... prior to 2013. That year, Eric Mamajek (University of Rochester) and his colleagues announced the discovery of Fomalhaut C, a companion star located a whopping 5.7° northwest of Fomalhaut (Alpha Piscis Austrini) in a different constellation, Aquarius.
Fomalhaut (FO-mal-ought) stands out as the only 1st-magnitude star among the fall constellations. For observers at mid-northern latitudes, it crouches low in the southern sky in the dim constellation Piscis Austrinus, the Southern Fish, and stands due south around 11:00 p.m. local time in early October (10:00 p.m. at mid-month).