Using a technique called astrometry, scientists have spotted an extrasolar planet that's thought to be the same size as its parent star... By contrast, Jupiter, the largest planet in our solar system, is only a tenth the width of the sun. The newfound gas giant, called VB 10b, orbits a red dwarf star, a relatively cool, small star less than half the mass of the sun. Although both are roughly the size of Jupiter, the planet orbits the star because the star is much more massive. VB 10b's discovery is the culmination of a 12-year search using an instrument at...