Barnard's Star

Barnard's Star holds the all-time record for proper motion: it streaks across the sky at 10.3 arcseconds per year, so that it shifts the equivalent of a full Moon's diameter roughly every 180 years. Astronomer Edward Emerson Barnard measured this staggering motion in 1916 from Yerkes Observatory, and the star bears his name as a result.

At 5.96 light-years away, it is the second-closest stellar system — after the Alpha/Proxima Centauri group — and the nearest single star to our Sun. It is a subdwarf of spectral class sdM4, meaning it is slightly metal-poor and smaller than a typical M4 dwarf. With roughly 16% of the Sun's mass and only 0.34% of its luminosity, it emits most of its feeble light in the infrared.

The search for planets around Barnard's Star has a long, tangled history. In the 1960s and 70s Peter van de Kamp claimed to detect planetary companions via astrometric wobble — claims that were later refuted. Patience was rewarded in 2024, when astronomers confirmed a sub-Earth-mass planet (Barnard b, ≥0.37 Earth masses) orbiting every 3.15 days, along with three additional sub-Earth candidates — the lowest-mass exoplanets detected around any nearby star at the time.

Its great age — around 10 billion years, more than twice the Sun's age — makes it one of the oldest red dwarfs in the solar neighbourhood. Its high velocity relative to the Sun (approximately 142 km/s) is consistent with membership in the old Population II, halo-like kinematic group of stars.