Barnard's Star (sometimes called Barnard's Runaway Star because of its large proper motion) is a very low-mass red dwarf star approximately 6 light-years away from Earth in the constellation of Ophiuchus (the Snake-holder). In 1916, American astronomer E. E. Barnard measured its proper motion as 10.3 arcseconds per year, which remains the largest known proper motion of any star relative to the Sun. At a distance of about 1.8 parsecs, or just under six light-years, Barnard's Star is the nearest known star in Ophiuchus, the second-closest known star system to the Sun, and the fourth-closest known individual star to the Sun, after the three components of the Alpha Centauri system. Despite its proximity, Barnard's Star is not visible with the unaided eye.