HD 102365

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HR 4523 A/B
Observation data
Epoch J2000      Equinox J2000
Constellation Centaurus
Right ascension 11h 46m 31.07263s[1]
Declination −40° 30′ 01.2722″[1]
Apparent magnitude (V) 4.88[2]/15[3]
Spectral type G2V[4]/M4V[5]
U−B color index 0.10[2]
B−V color index 0.67[2]
Radial velocity (Rv) 15.3 ± 0.9[6] km/s
Proper motion (μ) RA: −1530.99[1] mas/yr
Dec.: 403.67[1] mas/yr
Parallax (π) 108.45 ± 0.22[1] mas
Distance 30.07 ± 0.06 ly
(9.22 ± 0.02 pc)
Mass 0.889[7] M
Radius 0.96[7] R
Luminosity 0.85[8] L
Surface gravity (log g) 4.51[4] cgs
Temperature 5,643[8] K
Metallicity [Fe/H] −0.28[8] dex
Rotational velocity (v sin i) 0.5[9] km/s
Age 4.5–5.7[10] Gyr
Other designations
66 G. Centauri, GJ 442, HR 4523, CD -39°7301, HD 102365, LHS 311, LTT 4373, GCTP 2725.00, SAO 223020, HIP 57443.[11]
Database references

HR 4523 (66 G. Centauri) is a binary star system that is located in the northeastern part of the Centaurus constellation, at a distance of about 30.07 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.[5] This M-type star appears to be in a wide orbit around the primary at a current separation of about 211 astronomical units (AU),[5] (or 211 times the separation of the Earth from the Sun). By comparison, Neptune orbits at an average distance of 30 AU.

The stellar classification for the primary star in this system is G2V;[4] the same as the Sun. That of the red dwarf companion is M4V.[5] The primary star has an estimated 86%[12] to 89% the mass of the Sun, 96% of the Sun's radius,[7] and 85% of the Sun's luminosity.[8] It is a slow rotator, with a projected rotational velocity of 0.5 km/s.[9] Age estimates range from 4.5–5.7 billion years (Gyr)[10] up to 7.1 Gyr[13] or 9.48 Gyr.[7] Compared to the Sun, it only has about 52%[14] of the abundance of elements other than hydrogen and helium; what astronomers term the metallicity of a star.

This star system has a relatively large proper motion.[11] 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.[15] It has space velocity components [U, V, W] = [−67, −40, +4] km/s.[16]

Planetary system[edit]

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.[17] 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.[18]

The HD 102365 planetary system[19]
(in order from star)
Mass Semimajor axis
Orbital period
Eccentricity Inclination Radius
b 0.05 ± 0.008 MJ 0.46 ± 0.04 122.1 ± 0.3 0.34 ± 0.14


  1. ^ a b c d e van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752free to read, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357 
  2. ^ a b c Feinstein, A. (1966), "Photoelectric observations of Southern late-type stars", The Information Bulletin for the Southern Hemisphere, 8: 30, Bibcode:1966IBSH....8...30F 
  3. ^ 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 
  4. ^ a b c 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, arXiv:astro-ph/0603770free to read, Bibcode:2006AJ....132..161G, doi:10.1086/504637 
  5. ^ a b c d Raghavan, Deepak; et al. (September 2010), "A Survey of Stellar Families: Multiplicity of Solar-type Stars", The Astrophysical Journal Supplement, 190 (1): 1–42, arXiv:1007.0414free to read, Bibcode:2010ApJS..190....1R, doi:10.1088/0067-0049/190/1/1  For the adopted physical separation, see Table 11 in the appendix.
  6. ^ Evans, D. S. (June 20–24, 1966), "The Revision of the General Catalogue of Radial Velocities", Proceedings from IAU Symposium no. 30, London, England: Academic Press, p. 57, Bibcode:1967IAUS...30...57E 
  7. ^ a b c d Takeda, Genya; et al. (February 2007), "Structure and Evolution of Nearby Stars with Planets. II. Physical Properties of ~1000 Cool Stars from the SPOCS Catalog", The Astrophysical Journal Supplement Series, 168 (2): 297–318, arXiv:astro-ph/0607235free to read, Bibcode:2007ApJS..168..297T, doi:10.1086/509763 
  8. ^ a b c d Porto de Mello, G.; del Peloso, E. F.; Ghezzi, L. (2006), "Astrobiologically Interesting Stars Within 10 Parsecs of the Sun", Astrobiology, 6 (2): 308–331, arXiv:astro-ph/0511180free to read, Bibcode:2006AsBio...6..308P, doi:10.1089/ast.2006.6.308, PMID 16689649 
  9. ^ a b Schröder, C.; Reiners, A.; Schmitt, J. 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, Bibcode:2009A&A...493.1099S, doi:10.1051/0004-6361:200810377 
  10. ^ a b Mamajek, Eric E.; Hillenbrand, Lynne A. (November 2008), "Improved Age Estimation for Solar-Type Dwarfs Using Activity-Rotation Diagnostics", The Astrophysical Journal, 687 (2): 1264–1293, arXiv:0807.1686free to read, Bibcode:2008ApJ...687.1264M, doi:10.1086/591785 
  11. ^ a b "LHS 311 -- High proper-motion Star", SIMBAD, Centre de Données astronomiques de Strasbourg, retrieved 2011-10-11 
  12. ^ O'Toole, S. J.; et al. (August 2009), "The Frequency of Low-Mass Exoplanets", The Astrophysical Journal, 701 (2): 1732–1741, arXiv:0906.4619free to read, Bibcode:2009ApJ...701.1732O, doi:10.1088/0004-637X/701/2/1732 
  13. ^ 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, arXiv:0811.3982free to read, Bibcode:2009A&A...501..941H, doi:10.1051/0004-6361/200811191 
  14. ^ For a metallicity of [Fe/H] = −0.28 dex, the proportion of metals is given by 10−0.28, or 52%.
  15. ^ 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 
  16. ^ Gliese, W. (1969), "Catalogue of Nearby Stars. Edition 1969", Veröffentlichungen des Astronomischen Rechen-Instituts Heidelberg (22), Karlsruhe, Bibcode:1969VeARI..22....1G 
  17. ^ 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, Bibcode:2011ApJ...727..103T, doi:10.1088/0004-637X/727/2/103 
  18. ^ 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, arXiv:astro-ph/0611682free to read, Bibcode:2006ApJ...652.1674B, doi:10.1086/508449 
  19. ^ Schneider, Jean, "Planet : HD 102365 b", Extrasolar Planets Encyclopaedia, retrieved 2011-10-11 

External links[edit]