HR 4523 (66 G. Centauri) is a binary star system that is located in the northeastern part of the Centaurusconstellation, at a distance of about 30.07 ly (9.22 pc) from the Solar System. The larger member of the system is a G-type star that is smaller than the Sun but of similar mass. It has a common proper motion companion that was discovered by W. J. Luyten in 1960. This M-type star appears to be in a wide orbit around the primary at a current separation of about 211 astronomical units (AU), (or 211 times the separation of the Earth from the Sun). By comparison, Neptune orbits at an average distance of 30 AU.
This star system has a relatively large proper motion. The HR 4523 system is presently located within the Epsilon Indi Moving Group, although it gives itself away as an interloper, since the star is older and has a different composition than the group members. It has space velocity components = .
The primary star is believed to be orbited by a Neptune-like planet with a mass 16 times that of the Earth. The orbital period of this planet is 122.1 days. No other planets have been discovered orbiting this star. An examination of this system in the infrared did not reveal an excess emission that would otherwise suggest the presence of a circumstellar debris disk.
^ abcFeinstein, A. (1966), "Photoelectric observations of Southern late-type stars", The Information Bulletin for the Southern Hemisphere, 8: 30, Bibcode:1966IBSH....8...30F
^Poveda, A.; et al. (April 1994), "Statistical studies of visual double and multiple stars. II. A catalogue of nearby wide binary and multiple systems", Revista Mexicana de Astronomía y Astrofísica, 28 (1): 43-89, Bibcode:1994RMxAA..28...43P
^Evans, D. S. (June 20-24, 1966), "The Revision of the General Catalogue of Radial Velocities", Proceedings from IAU Symposium no. 30, 30, London, England: Academic Press, p. 57, Bibcode:1967IAUS...30...57E