Nature 436, 230-233 (14 July 2005) | doi:10.1038/nature03856; Received 15 April 2005; Accepted 23 May 2005

An extrasolar giant planet in a close triple-star system

Maciej Konacki1

  1. California Institute of Technology, Division of Geological & Planetary Sciences MC 150-21, Pasadena, California 91125, USA

Correspondence to: Maciej Konacki1 Correspondence and requests for materials should be addressed to M.K. (Email: maciej@gps.caltech.edu).

Hot Jupiters are gas-giant planets orbiting with periods of 3–9 days around Sun-like stars. They are believed to form in a disk of gas and condensed matter at or beyond approx2.7 astronomical units (au—the Sun–Earth distance) from their parent star1, 2. At such distances, there exists a sufficient amount of solid material to produce a core capable of capturing enough gas to form a giant planet. Subsequently, they migrate inward to their present close orbits3. Here I report the detection of an unusual hot Jupiter orbiting the primary star of a triple stellar system, HD 188753. The planet has an orbital period of 3.35 days and a minimum mass of 1.14 times that of Jupiter. The primary star's mass is 1.06 times that of the Sun, 1.06 M circle dot. The secondary star, itself a binary stellar system, orbits the primary at an average distance of 12.3 au with an eccentricity of 0.50. The mass of the secondary pair is 1.63 M circle dot. Such a close and massive secondary would have truncated a disk around the primary to a radius of only approx1.3 au (ref. 4) and might have heated it up to temperatures high enough to prohibit giant-planet formation5, 6, leaving the origin of this planet unclear.