Hugh Pickens writes writes "Only 4 stars, including Barnard's Star, are within 6 light years of the Sun, and only 11 are within 10 light years. That's why Barnard's star, popularized in Robert Forward's hard-sf novel, "Flight of the Dragonfly," is often short-listed as a target for humanity's first interstellar probe. Astronomers have long hoped to find a habitable planet around it, an alien Earth that might someday bear the boot prints of a future Neil Armstrong, or the tire tracks of a souped-up 25th-century Curiosity rover. But now Ross Anderson reports that a group of researchers led by UC Berkeley's Jieun Choi have delivered the fatal blow to Barnard's Star when they revealed the results of 248 precise Doppler measurements that were designed to examine the star for wobbles indicative of planets around it. The measurements, taken over a period of 25 years, led to a depressing conclusion: "the habitable zone around Barnard's star appears to be devoid of roughly Earth-mass planets or larger . . . [p]revious claims of planets around the star by van de Kamp are strongly refuted." NASA's Kepler space telescope, which studies a group of distant Milky Way stars, has found more than 2,000 exoplanet candidates in just the past two years, leading many to suspect that our galaxy is home to billions of planets, a sizable portion of which could be habitable. "This non-detection of nearly Earth-mass planets around Barnard’s Star is surely unfortunate, as its distance of only 1.8 parsecs would render any Earth-size planets valuable targets for imaging and spectroscopy, as well as compelling destinations for robotic probes by the end of the century.""