Astrometry

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 planetThe term "planet" originally comes from the Greek word for "wanderer" since these objects were seen to move in the sky independently from the background of fixed stars that moved together through the seasons. The IAU last defined the term planet in 2006, however the new definition has remained controversial. is present, its gravitational influence will cause the starSelf-luminous object held together by its own self-gravity. Often refers to those objects which generate energy from nuclear reactions occurring at their cores, but may also be applied to stellar remnants such as neutron stars. to move in a tiny circular or elliptical orbitDescribes the characteristic oval orbital path of planets and asteroids around the Sun. about their barycenter. This method is most sensitive to giant planets with large orbits. The Hubble Space TelescopeA 2.4-meter reflecting telescope, which was deployed in low-Earth orbit (600 kilometers) by the crew of the space shuttle Discovery (STS-31) on 25 April 1990. The Hubble Space Telescope is a cooperative program of the European Space Agency (ESA) and the National Aeronautics and Space Administration (NASA). HST's current complement was used in 2002 to make astrometric measurements to characterize the orbitThe elliptical path of one body around another, typically the path of a small body around a much larger body. However, depending on the mass distribution of the objects, they may rotate around an empty spot in space • The Moon orbits around the Earth. • The Earth orbits around of a previously discovered planet around Gliese 876b.