Our galaxy is a big place, but that doesn't mean we don't have any neighbors. There are a handful of stars close enough to Earth to be potential targets for exploration within our lifetimes. The hope was that one of the closest of these, Barnard's Star, just might have a habitable planet in orbit, but new observations show no signs of anything at all.
First, we should point out that Barnard's Star is really the fourth closest star to Earth. The first three, though, are all part of one single system: Alpha Centauri, which consists of a pair of stars orbiting each other along with a third, gravitationally associated star (called Proxima Centauri) that's much smaller and orbits much farther away. It may be possible for a habitable planet to exist somewhere in that mess of gravity and orbits, but it's not the friendliest sort of system.
Barnard's Star, on the other hand, is much more promising. It's a low mass red dwarf, much smaller and older than the sun, and would provide a calm and stable environment for any Earth-like planets that happened to be in orbit around it. It was promising enough, in fact, that the very first realistic concept for an interstellar exploration mission, Project Daedalus, chose Bernard's Star as its destination, despite the fact that it's several light-years farther from Earth than Alpha Centauri is.
However, a paper published by UC Berkeley researchers last week using a series 136 precise Doppler measurements taken over a period of eight years seems to have thrown out Barnard's Star as a potential host for planets. According to the researchers, "the habitable zone of Barnard's Star appears to be devoid of roughly Earth-mass planets or larger." Sadface. The paper continues to twist the knife by pointing out that:
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.
Yes. Thank you for driving that home. Sigh.
The really unfortunate bit, though, is that this seems to be just bad luck that we got stuck next to a boring red dwarf, since spectrographic surveys suggest that the Earthish planets occur in habitable zones in around 40% of all red dwarf stars out there. That's a big percentage, but it's not particularly helpful to us here on Earth at the moment, and it's now looking like we might have to travel a bit farther afield to find our first Risa, or even our first Ceti Alpha V.