Astronomy:HD 102365

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Short description: Binary star system in the constellation Centaurus
HD 102365
Observation data
{{#ifeq:J2000|J2000.0 (ICRS)|Epoch J2000.0      Equinox J2000.0 (ICRS)| Epoch J2000      [[Astronomy:Equinox (celestial coordinates)|Equinox J2000}}
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[2] mas/yr
Dec.: +403.287[2] mas/yr
Parallax (π)107.3024 ± 0.0873[2] mas
Distance30.40 ± 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
Dec.: +381.396 mas/yr
Parallax (π)107.4237 ± 0.0351[4] mas
Distance30.362 ± 0.010 ly
(9.309 ± 0.003 pc)
Details
A
Mass0.79+0.03
−0.02[9] M☉
Radius0.99±0.02[10] R☉
Luminosity0.86±0.05[10] L☉
Habitable zone inner limit0.887[9] AU
Habitable zone outer limit1.573[9] AU
Surface gravity (log g)4.44±0.03[10] cgs
Temperature5,594+49
−50[10] K
Metallicity [Fe/H]−0.34±0.04[9] dex
Rotation36.4±7.3[9] days
Rotational velocity (v sin i)0.5[11] km/s
Age11.0±0.9[12] Gyr
B
Mass0.192[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
SIMBADA
B
Exoplanet Archivedata
ARICNSdata

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.

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]

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.[24]

The HD 102365 planetary system[20]
Companion
(in order from star) 		Mass Semimajor axis
(AU) 		Orbital period
(days) 		Eccentricity Inclination Radius
b (controversial[9][23]) ≥9.34+1.52
−1.5 M⊕ 		0.46±0.04 121.3±0.25 0.28±0.15 — —

References

  1. ↑ Roman, Nancy G. (1987). "Identification of a constellation from a position". Publications of the Astronomical Society of the Pacific 99 (617): 695. doi:10.1086/132034. Bibcode: 1987PASP...99..695R  Constellation record for this object at VizieR.
  2. ↑ 2.0 2.1 2.2 2.3 2.4 Vallenari, A. et al. (2022). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy & Astrophysics. doi:10.1051/0004-6361/202243940  Gaia DR3 record for this source at VizieR.
  3. ↑ 3.0 3.1 3.2 Feinstein, A. (1966), "Photoelectric observations of Southern late-type stars", The Information Bulletin for the Southern Hemisphere 8: 30, Bibcode: 1966IBSH....8...30F 
  4. ↑ 4.0 4.1 4.2 4.3 Vallenari, A. et al. (2022). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy & Astrophysics. doi:10.1051/0004-6361/202243940  Gaia DR3 record for this source at VizieR.
  5. ↑ 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 
  6. ↑ 6.0 6.1 Gray, R. O. et al. (July 2006), "Contributions to the Nearby Stars (NStars) Project: Spectroscopy of Stars Earlier than M0 within 40 pc-The Southern Sample", The Astronomical Journal 132 (1): 161–170, doi:10.1086/504637, Bibcode: 2006AJ....132..161G 
  7. ↑ 7.0 7.1 7.2 7.3 Raghavan, Deepak et al. (September 2010), "A Survey of Stellar Families: Multiplicity of Solar-type Stars", The Astrophysical Journal Supplement 190 (1): 1–42, doi:10.1088/0067-0049/190/1/1, Bibcode: 2010ApJS..190....1R  For the adopted physical separation, see Table 11 in the appendix.
  8. ↑ Holmberg, J.; Nordström, B.; Andersen, J. (July 2009), "The Geneva-Copenhagen survey of the solar neighbourhood. III. Improved distances, ages, and kinematics", Astronomy and Astrophysics 501 (3): 941–947, doi:10.1051/0004-6361/200811191, Bibcode: 2009A&A...501..941H 
  9. ↑ 9.0 9.1 9.2 9.3 9.4 9.5 9.6 Figueira, P.; Faria, J. P.; Silva, A. M.; Castro-González, A.; Silva, J. Gomes da; Sousa, S. G.; Bossini, D.; Zapatero-Osorio, M. R. et al. (2025-07-10), "A comprehensive study on radial velocity signals using ESPRESSO: Pushing precision to the 10 cm/s level", Astronomy and Astrophysics 700: A174, doi:10.1051/0004-6361/202553869, Bibcode: 2025A&A...700A.174F 
  10. ↑ 10.0 10.1 10.2 10.3 10.4 Harada, Caleb K. et al. (June 2024), "Setting the Stage for the Search for Life with the Habitable Worlds Observatory: Properties of 164 Promising Planet-survey Targets", The Astrophysical Journal Supplement Series 272 (2): id. 30, doi:10.3847/1538-4365/ad3e81, Bibcode: 2024ApJS..272...30H 
  11. ↑ 11.0 11.1 Schröder, C.; Reiners, Ansgar; Schmitt, Jürgen H. M. M. (January 2009), "Ca II HK emission in rapidly rotating stars. Evidence for an onset of the solar-type dynamo", Astronomy and Astrophysics 493 (3): 1099–1107, doi:10.1051/0004-6361:200810377, Bibcode: 2009A&A...493.1099S 
  12. ↑ 12.0 12.1 Nissen, P. E.; Christensen-Dalsgaard, J.; Mosumgaard, J. R.; Silva Aguirre, V.; Spitoni, E.; Verma, K. (August 2020), "High-precision abundances of elements in solar-type stars: Evidence of two distinct sequences in abundance-age relations", Astronomy & Astrophysics 640: A81, doi:10.1051/0004-6361/202038300, ISSN 0004-6361, Bibcode: 2020A&A...640A..81N 
  13. ↑ Mugrauer, M. (December 2019), "Search for stellar companions of exoplanet host stars by exploring the second ESA-Gaia data release", Monthly Notices of the Royal Astronomical Society 490 (4): 5088–5102, doi:10.1093/mnras/stz2673, Bibcode: 2019MNRAS.490.5088M 
  14. ↑ 14.0 14.1 "HD 102365". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=HD+102365. 
  15. ↑ Gould, Benjamin Apthorp (1879), "Uranometria Argentina catalog of bright southern stars", Resultados del Observatorio Nacional Argentino en Cordoba (Buenos Aires) 1, Bibcode: 1879RNAO....1.....G, http://vizier.u-strasbg.fr/viz-bin/VizieR?-source=V%2F135%2Fcatalog, retrieved 2012-05-08 
  16. ↑ Casali, G.; Spina, L.; Magrini, L.; Karakas, A. I.; Kobayashi, C.; Casey, A. R.; Feltzing, S.; Swaelmen, M. Van der et al. (2020-07-01), "The Gaia-ESO survey: the non-universality of the age–chemical-clocks–metallicity relations in the Galactic disc" (in en), Astronomy & Astrophysics 639: A127, doi:10.1051/0004-6361/202038055, ISSN 0004-6361, Bibcode: 2020A&A...639A.127C 
  17. ↑ For a metallicity of [Fe/H] = −0.28 dex, the proportion of metals is given by 10−0.28, or 52%.
  18. ↑ Kovacs, N.; Foy, R. (1978), "A detailed analysis of three stars in the Eggen's Epsilon INDI moving group", Astronomy and Astrophysics 68 (1–2): 27–31, Bibcode: 1978A&A....68...27K 
  19. ↑ Gliese, W. (1969), "Catalogue of Nearby Stars. Edition 1969", Veröffentlichungen des Astronomischen Rechen-Instituts Heidelberg, 22, Karlsruhe, p. 1, Bibcode: 1969VeARI..22....1G 
  20. ↑ 20.0 20.1 20.2 Laliotis, Katherine et al. (February 2023), "Doppler Constraints on Planetary Companions to Nearby Sun-like Stars: An Archival Radial Velocity Survey of Southern Targets for Proposed NASA Direct Imaging Missions", The Astronomical Journal 165 (4): 176, doi:10.3847/1538-3881/acc067, Bibcode: 2023AJ....165..176L 
  21. ↑ 21.0 21.1 Tinney, C. G. et al. (2011), "The Anglo-Australian Planet Search. XX. A Solitary Ice-giant Planet Orbiting HD 102365", The Astrophysical Journal 727 (2): 103, doi:10.1088/0004-637X/727/2/103, Bibcode: 2011ApJ...727..103T 
  22. ↑ Zechmeister, M. et al. (April 2013), "The planet search programme at the ESO CES and HARPS. IV. The search for Jupiter analogues around solar-like stars", Astronomy & Astrophysics 552: A78, doi:10.1051/0004-6361/201116551, Bibcode: 2013A&A...552A..78Z 
  23. ↑ 23.0 23.1 Harada, Caleb K.; Dressing, Courtney D.; Turtelboom, Emma V.; Kane, Stephen R.; Blunt, Sarah; Dietrich, Jamie; Hinkel, Natalie R.; Li, Zhexing et al. (2025-09-23), "SPORES-HWO. II. Companion Mass Limits and Updated Planet Properties for 120 Future Exoplanet Imaging Targets from 35 Years of Precise Doppler Monitoring", The Astronomical Journal 
  24. ↑ Beichman, C. A. et al. (December 2006), "New Debris Disks around Nearby Main-Sequence Stars: Impact on the Direct Detection of Planets", The Astrophysical Journal 652 (2): 1674–1693, doi:10.1086/508449, Bibcode: 2006ApJ...652.1674B 



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