HD 102365
Binary star system in the constellation Centaurus
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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.
 | |
| Observation data Epoch J2000 Equinox ICRS | |
|---|---|
| Constellation | Centaurus[1] |
| A | |
| Right ascension | 11h 46m 31.07253s[2] |
| Declination | −40° 30′ 01.2859″[2] |
| Apparent magnitude (V) | 4.88[3] |
| B | |
| Right ascension | 11h 46m 32.68988s[4] |
| Declination | −40° 29′ 47.6048″[4] |
| Apparent magnitude (V) | 15[5] |
| Characteristics | |
| Spectral type | G2V[6] + M4V[7] |
| U−B color index | 0.10[3] |
| B−V color index | 0.67[3] |
| Astrometry | |
| A | |
| Radial velocity (Rv) | 16.94±0.12[2] km/s |
| Proper motion (μ) | RA: −1530.971 mas/yr[2] Dec.: +403.287 mas/yr[2] |
| Parallax (π) | 107.3024±0.0873 mas[2] |
| Distance | 30.40 ± 0.02 ly (9.319 ± 0.008 pc) |
| Absolute magnitude (MV) | 5.07[8] |
| B | |
| Radial velocity (Rv) | 17.23±0.27[4] km/s |
| Proper motion (μ) | RA: −1534.679 mas/yr[4] Dec.: +381.396 mas/yr[4] |
| Parallax (π) | 107.4237±0.0351 mas[4] |
| Distance | 30.362 ± 0.010 ly (9.309 ± 0.003 pc) |
| Details | |
| A | |
| Mass | 0.79+0.03 −0.02[9] M☉ |
| Radius | 0.99±0.02[10] R☉ |
| Luminosity | 0.86±0.05[10] L☉ |
| Habitable zone inner limit | 0.887[9] AU |
| Habitable zone outer limit | 1.573[9] AU |
| Surface gravity (log g) | 4.44±0.03[10] cgs |
| Temperature | 5,594+49 −50[10] K |
| Metallicity [Fe/H] | −0.34±0.04[9] dex |
| Rotation | 36.4±7.3[9] days |
| Rotational velocity (v sin i) | 0.5[11] km/s |
| Age | 11.0±0.9[12] Gyr |
| B | |
| Mass | 0.192[13] M☉ |
| Other designations | |
| 66 G. Cen, CD−39°7301, GJ 442, HD 102365, HIP 57443, HR 4523, SAO 223020, LHS 311, LTT 4373, PLX 2725.00[14][15] | |
| B: LHS 313, VB 5 | |
| Database references | |
| SIMBAD | A |
| B | |
| Exoplanet Archive | data |
| ARICNS | data |
Description
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]
Search for planets
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] Similarly, another 2025 paper also reported a non-detection.[23] The NASA Exoplanet Archive demoted the planet to false positive status in April 2026.[24]
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.[25]