Centennial of the Discovery of the Proper Motion of Barnard’s Star

2016, in addition to being the 125^th anniversary of Ladd Observatory, is also the 100^th anniversary of the discovery of a star moving the fastest in our sky.  In 1916, Edward Emerson Barnard, working at the Yerkes Observatory’s 40” refractor, discovered that a very tiny red dwarf star’s proper motion had the incredible rate of 10.3” per year.  Although to us this may sound like watching fingernails grow, on the celestial sphere this is incredible.  It is the equivalent of traveling the diameter of our Moon in under two centuries. 

Proper motion is the change in position of a star on the celestial sphere from our perspective.  This change is normally exceedingly small, often seconds of arc per century.   It is believed the first person who realized this motion was Edmund Halley, who in 1718 noticed that some of our closer stars’ positions differed from that of Hipparchus’s charts two millennia previous. 

Besides moving very quickly, Barnard’s star is the fourth closest to us, only about 6 light years.  Only the Alpha Centauri system of three stars, at 4 ¼ light years, is closer. 

Unfortunately, Barnard’s star isn’t in our evening sky right now, as it is within the constellation Ophiuchus, the Doctor, which belongs to our spring/summer set of stars.  It also, at approximately 9^th apparent magnitude, is close to 15 times dimmer than the sharpest eyes can locate, but, it is rather easy to find with a small telescope; however, don’t expect to be enthralled, as this star is not very significant, even with the best instruments.  But, remember:  whenever you are able to look at it, it will never be in the same position again.