Astrometry

Gliese wobble
Image Source: hubblesite.org

Branch of astronomy entailing measurements of the positions of stars and other celestial bodies. It is the oldest search method for extrasolar planets, using precise measurements of a star’s position in sky over a long period of time (years, decades) to look for shifts (wobbles) in position relative to other more distant stars. If a planet is present, its gravitational influence will cause the star to move in a tiny circular or elliptical orbit about their barycenter. This method is most sensitive to giant planets with large orbits. The Hubble Space Telescope was used in 2002 to make astrometric measurements to characterize the orbit of a previously discovered planet around Gliese 876b.


Some or all content above used with permission from J. H. Wittke.