Astrometry Finally Bags an Exoplanet

Using the method of astrometry to find planets orbiting other stars has been around for 50 years, and until now it hasn’t bagged a single exoplanet. But finally, astronomers found a Jupiter-sized planet , called VB 10b, using this method. Astrometry is difficult and requires very precise measurements over long periods of time. So why did they keep trying for so long? “This method is optimal for finding solar-system configurations like ours that might harbor other Earths,” said astronomer Steven Pravdo of JPL. “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 10 stars are small like this one, this could mean planets are more common than we thought.”

The finding confirms that astrometry could be a powerful planet-hunting technique for both ground- and space-based telescopes. For example, a similar technique would be used by SIM Lite, a NASA concept for a space-based mission that is currently being explored.

The newfound exoplanet is about 20 light-years away in the constellation Aquila. It is a gas giant, with a mass six times that of Jupiter’s, and an orbit far enough away from its star to be labeled a “cold Jupiter” similar to our own. In reality, the planet’s own internal heat would give it an Earth-like temperature.

The planet’s star, called VB 10, is tiny. It is what’s known as an M-dwarf and is only one-twelfth the mass of our sun, just barely big enough to fuse atoms at its core and shine with starlight. For years, VB 10 was the smallest star known — now it has a new title: the smallest star known to host a planet. In fact, though the star is more massive than the newfound planet, the two bodies would have a similar girth.

They tried this with Bernard's Star and failed to find anything...despite some misstarts.