From the January 2024 issue

Barnard’s Star

By | Published: January 1, 2024

Barnard’s Star is a magnitude 9.5 star moving almost due north against the stars of Ophiuchus at a rate of 1° every 351 years. This, the highest proper motion known of any star, is due to a combination of factors: The star lies less than 6 light-years away (the next closest star to our Sun after the Alpha Centauri system) and it is moving toward us at 68 miles per second (110 km/s), indicating a total velocity of about 89 miles per second (143 km/s).

Edward Emerson Barnard discovered the star in 1916, while comparing images he had taken in 1894 and 1916 with a blink comparator. This apparatus allows two photographic plates of the same part of the sky to be compared quickly in succession.

For decades, astronomers have been scratching their heads over a wobble that Barnard’s Star exhibits as it moves across the sky. Some astronomers claimed the wobble is due to a gravitational tug-of-war between the star and planetary companions. But to date, observations have failed to reveal any large Jupiter- or brown-dwarf-sized objects, down to a limit of about 0.4 Jupiter mass. One 2018 study claimed that an object three times the mass of Earth was found; however, this was considered a false positive. Although the idea of planets orbiting Barnard’s Star is fading from view, a final verdict in this case has not been reached.

Like Proxima Centauri, Barnard’s Star is a red dwarf, possibly an old disk star that formed before our galaxy became enriched with heavy elements. Barnard’s Star shines brightly enough to be spied through the smallest of telescopes. It will pass closest to Earth (3.9 light-years) in just under 10,000 years. By that time, the star’s proper motion will have increased, and its brightness will have grown significantly.