Barnard's star, star with the largest observed proper motion (rate of motion across the sky with respect to other stars); located in the constellation Ophiuchus. The star's large proper motion, 10.28″ per year (or half the moon's apparent diameter in a century), is due in part to the fact that it is the second-nearest star, being at a distance of 5.98 light-years. Barnard's star was discovered in 1916 by E. E. Barnard, an observer known also for his discoveries of 16 comets. It is a faint red dwarf star, apparent magnitude 9.5, of spectral class M5, lying near the bottom of the main sequence in the Hertzsprung-Russell diagram. Slight oscillations in its motion indicate that it has at least one unseen companion.