51 Pegasi b

51 Pegasi b (51 Peg b) is a hot Jupiter of roughly half a Jupiter mass, orbiting a G-type star, but close to the star with an orbital period of a little more than 4 Earth days. It was identified in 1995 using the ELODIE spectrograph on the OHP 1.93 m telescope (of France's Haute-Provence Observatory, OHP), and it was the first extra-solar planet discovered that orbits a main sequence star. Its orbital radius and its mass are derived from the star's radial velocity variation and the star's mass suggested by its spectral type. Other planet characteristics ascribed to it are modeled based on these. Its larger-than-Jupiter radius is presumed because of its presumed high temperature. Characteristics:

• Host star: 51 Pegasi (51 Peg).
• Discovery: by the radial velocity method in 1995.
• 50.6 ly - distance.
• 0.05 AU - orbital radius (semi-major axis).
• 4.2 days - orbital period.
• 0.46 - Jupiter masses.
• 1.2 - radius in Jupiter radii.
• 1265 K - predicted temperature.