Only four light years away, and it's about the same size as Earth... and now we get a mystery signal, so aliens? By Jon Fingas via Yahoo News Astronomers have encountered a mystery surprisingly close to Earth. The Guardian and Scientific American have learned that Breakthrough Listen astronomers using the Parkes telescope in Australia discovered a strange radio signal coming from Proxima Centauri, the star system closest to the Sun. The signal occupies an oddly narrow 982MHz band that's unused by human-made spacecraft, yet not possible through known natural processes. The frequency shifts up, too, rather than down like you'd expect for a planet. Don't count on this as a sign of aliens. Although Proxima Centauri does host a potentially habitable planet, the signal hasn't been detected since its initial observation between April and May 2019. Breakthrough Listen said it was still "carefully investigating" and that unusual signals are typically interference researchers couldn't "fully