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HD 102365
Binary star system in the constellation Centaurus From Wikipedia, the free encyclopedia
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HD 102365 (66 G. Centauri) is a binary star system that is located in the northeastern part of the Centaurus constellation, at a distance of about 30.4 light-years (9.3 parsecs) 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.[7] This M-type star appears to be in a wide orbit around the primary at a current separation of about 211 astronomical units (AU),[7] (or 211 times the separation of the Earth from the Sun). By comparison, Neptune orbits at an average distance of 30 AU.
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The stellar classification for the primary star in this system is G2V;[6] the same as the Sun. That of the red dwarf companion is M4V.[7] The primary star has an estimated 84% the mass of the Sun, 99% of the Sun's radius, and 86% of the Sun's luminosity.[10] It is a slow rotator, with a projected rotational velocity of 0.5 km/s.[11] The system is believed to be ancient, with modern estimates of the age between 11.0[12] and 13.1 billion years,[16] over double that of the Solar System. Compared to the Sun, it only has about 52% of the abundance of elements other than hydrogen and helium; what astronomers term the metallicity of a star.[17]
This star system has a relatively large proper motion.[14] 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.[18] It has space velocity components [U, V, W] = [−67, −40, +4] km/s.[19]
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The primary star has been believed to be orbited by a Neptune-like planet with a minimum mass 9.3 times that of the Earth.[20] The orbital period of this planet is 122.1 days. No other planets have been discovered orbiting this star.[21] Initially detected in 2012 by Doppler spectroscopy (radial velocity method),[21] a 2013 study was unable to confirm this planet,[22] but it was detected again in a 2023 study. Evidence suggested the radial velocity variations are indeed caused from the orbital motion of a planet, and not from intrinsic processes arising from the star.[20]: 27 However, it was again undetected in ESPRESSO observations taken by a 2025 study, which found evidence that the radial velocity variations instead arise from the star's magnetic field.[9]
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.[23]
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