The star in question is a red dwarf called VB 10. For a time it was one of the smallest stars known to exist. Red dwarfs are the most common type of star in the Galaxy, and are the coolest. This means that the habitable zone around stars like VB 10 – in other words, the region around the star where the temperature is just right for liquid water – will be much, much closer to the star. If an Earth-like world exists around VB 10 it will be between the star and the gas giant.

What is novel about this new discovery is the method by which the planet was found. Stuart Shaklan and Steven Pravdo from NASA’s Jet Propulsion Laboratory spent a dozen years watching for tiny wobbles in the proper motions of stars as they traverse across the night sky. This isn’t to be confused with the radial velocity method in which a planet induces a wobble in a star as it rotates on its axis.

This new astrometric method was actually first attempted 50 years ago, but accurate enough observations could not be made of the motions of stars. Now Pravda and Shaklan have shown that it is possible, using 16-megapixel CCD cameras strapped to the Hale Telescope at Mount Palomar in California.

“The method is optimal for finding solar system configurations like ours that might harbour other Earths,” says Pravda. “We found a Jupiter-like planet at around the same relative place as our Jupiter, only around a much smaller star. It’s possible this star also has inner rocky planets. And since more than seven out of ten stars are small like this one, this could mean planets are more common than we thought.”

Readers might like to view a video that shows the wobble in the proper motion of VB 10 at NASA's website here.