The planet is called Proxima b, but the lack of nomenclatural creativity is soon forgiven when considering the precision of the astrometry. Here they measure the speed at which a star, 4-something light years away, move relative to us ... to a precision of a few km/hr! It is based on such measurements (which almost certainly have to be at the limit of what can ever be detected), that the new planet around Proxima was announced this week.
Nice write-up here. http://earthsky.org/space/next-nearest-star-has-a-planet