{{Short description|Binary star system in the constellation Centaurus}} {{Starbox begin}} {{Starbox image | image = {{Location mark |image=Centaurus constellation map.svg|alt=|float=center|width=280 |label=|position=right |mark=Red circle.svg|mark_width=10|mark_link=HD 102365 |x=950|y=480 }} | caption = Location of HD 102365 (circled in red) }} {{Starbox observe 2s | epoch = J2000 | constell = [[Centaurus]]<ref name=constellation/> | component1 = A | ra1 = {{RA|11|46|31.07253}}<ref name=GaiaDR3a/> | dec1 = {{DEC|−40|30|01.2859}}<ref name=GaiaDR3a/> | appmag_v1 = 4.88<ref name=ibsh8_30/> | component2 = B | ra2 = {{RA|11|46|32.68988}}<ref name=GaiaDR3b/> | dec2 = {{DEC|−40|29|47.6048}}<ref name=GaiaDR3b/> | appmag_v2 = 15<ref name=rmaa28_1_43/> }} {{Starbox character | class = G2V<ref name=apj132_1_161/> + M4V<ref name=aphs190_1_1/> | b-v = 0.67<ref name=ibsh8_30/> | u-b = 0.10<ref name=ibsh8_30/> | variable = }} {{Starbox astrometry | component1 = A | radial_v = {{val|16.94|0.12}}<ref name=GaiaDR3a/> | prop_mo_ra = −1530.971 | prop_mo_dec = +403.287 | pm_footnote = <ref name=GaiaDR3a/> | parallax = 107.3024 | p_error = 0.0873 | parallax_footnote = <ref name=GaiaDR3a/> | absmag_v = 5.07<ref name=aaa501_3_941/> | component2 = B | radial_v2 = {{val|17.23|0.27}}<ref name=GaiaDR3b/> | prop_mo_ra2 = −1534.679 | prop_mo_dec2 = +381.396 | pm_footnote2 = <ref name=GaiaDR3b/> | parallax2 = 107.4237 | p_error2 = 0.0351 | parallax_footnote2 = <ref name=GaiaDR3b/> | absmag_v2 = }} {{Starbox detail | component1 = A | mass = {{Val|0.79|0.03|0.02}}<ref name=Figueira2025/> | radius = {{Val|0.99|0.02}}<ref name=Harada2024/> | luminosity = {{Val|0.86|0.05}}<ref name=Harada2024/> | temperature = {{Val|5594|49|50|fmt=commas}}<ref name=Harada2024/> | metal_fe = {{val|-0.34|0.04}}<ref name=Figueira2025/> | habitable_inner = 0.887<ref name=Figueira2025/> [[astronomical unit|AU]] | habitable_outer = 1.573<ref name=Figueira2025/> AU | gravity = {{Val|4.44|0.03}}<ref name=Harada2024/> | rotation = {{Val|36.4|7.3}}<ref name=Figueira2025/> days | rotational_velocity = 0.5<ref name=aaa493_3_1099/> | age_gyr = {{Val|11.0|0.9}}<ref name=Nissen2020/> | component2 = B | mass2 = 0.192<ref name="Mugrauer2019"/> }} {{Starbox catalog | names = {{odlist | Gould=66 G. Cen | GJ=442 | HR=4523 | CD=−39°7301 | HD=102365 | LHS=311 | LTT=4373 | PLX=2725.00 | SAO=223020 | HIP=57443 }}<ref name=SIMBAD/><ref name=Gould1879/> | component2 = B | names2 = {{odlist | LHS=313}}, [[Van Biesbroeck's star catalog|VB]] 5 }} {{Starbox reference | Simbad=LHS+311 | sn=A | Simbad2=GJ+442+B | sn2=B | NSTED=HD-102365 | ARICNS=00904 }} {{Starbox end}}
'''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 {{Convert|30.4|ly|pc|lk=on|abbr=off}} 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 [[Willem Jacob Luyten|W. J. Luyten]] in 1960.<ref name=aphs190_1_1/> This M-type star appears to be in a wide orbit around the primary at a current separation of about 211 [[astronomical unit]]s (AU),<ref name=aphs190_1_1/> (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;<ref name=apj132_1_161/> the same as the Sun. That of the [[red dwarf]] companion is M4V.<ref name=aphs190_1_1/> The primary star has an estimated 84% the [[Solar mass|mass of the Sun]], 99% of the [[Solar radius|Sun's radius]], and 86% of the [[Solar luminosity|Sun's luminosity]].<ref name=Harada2024/> It is a slow rotator, with a [[stellar rotation|projected rotational velocity]] of 0.5 km/s.<ref name=aaa493_3_1099/> The system is believed to be ancient, with modern estimates of the age between 11.0<ref name=Nissen2020/> and 13.1 billion years,<ref name=Casali2020/> 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.<ref name=metal/>
This star system has a relatively large proper motion.<ref name=SIMBAD/> 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.<ref name=aaa68_1_27/> It has [[space velocity (astronomy)|space velocity]] components {{nowrap|[''U'', ''V'', ''W'']}} = {{nowrap|[−67, −40, +4] km/s}}.<ref name=gliese1969/>
== 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.<ref name="Laliotis2023"/> The orbital period of this planet is 122.1 days. No other planets have been discovered orbiting this star.<ref name=apj727_103/> Initially detected in 2012 by [[Doppler spectroscopy]] (radial velocity method),<ref name=apj727_103/> a 2013 study was unable to confirm this planet,<ref name="Zechmeister2013"/> 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.<ref name="Laliotis2023"/>{{rp|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]].<ref name=Figueira2025/> Similarly, another 2025 paper also reported a non-detection.<ref name=Harada2025/> The [[NASA Exoplanet Archive]] demoted the planet to false positive status in April 2026.<ref>{{cite web |date=9 April 2026 |title=2026 Exoplanet Archive News |url=https://exoplanetarchive.ipac.caltech.edu/docs/exonews_archive.html#9April2026 |website=[[NASA Exoplanet Archive]] |access-date=26 April 2026 |quote=We've also updated the dispositions of HD 102365 b and HD 10700 e (a.k.a. tau Cet e) to False Positive Planet based on a published refutation.}}</ref>
An examination of this system in the [[infrared]] did not reveal an [[infrared excess|excess emission]] that would otherwise suggest the presence of a circumstellar [[debris disk]].<ref name=apj652_2_1674/>
==References== <references> <ref name=GaiaDR3a>{{Cite Gaia DR3|5381537023379295232}}</ref> <ref name=GaiaDR3b>{{Cite Gaia DR3|5381537023379295744}}</ref>
<ref name=constellation>{{cite constellation|HD 102365}}</ref>
<ref name=ibsh8_30>{{citation | last1=Feinstein | first1=A. | title=Photoelectric observations of Southern late-type stars | journal=The Information Bulletin for the Southern Hemisphere | volume=8 | page=30 | year=1966 | bibcode=1966IBSH....8...30F }}</ref>
<ref name=apj132_1_161>{{citation | display-authors=1 | last1=Gray | first1=R. O. | last2=Corbally | first2=C. J. | last3=Garrison | first3=R. F. | last4=McFadden | first4=M. T. | last5=Bubar | first5=E. J. | last6=McGahee | first6=C. E. | last7=O'Donoghue | first7=A. A. | last8=Knox | first8=E. R. | title=Contributions to the Nearby Stars (NStars) Project: Spectroscopy of Stars Earlier than M0 within 40 pc-The Southern Sample | journal=The Astronomical Journal | volume=132 | issue=1 | pages=161–170 |date=July 2006 | doi=10.1086/504637 | bibcode=2006AJ....132..161G |arxiv = astro-ph/0603770 | s2cid=119476992 }}</ref>
<ref name=aphs190_1_1>{{citation | display-authors=1 | last1=Raghavan | first1=Deepak | last2=McAlister | first2=Harold A. | last3=Henry | first3=Todd J. | last4=Latham | first4=David W. | last5=Marcy | first5=Geoffrey W. | last6=Mason | first6=Brian D. | last7=Gies | first7=Douglas R. | last8=White | first8=Russel J. | last9=ten Brummelaar | first9=Theo A. | title=A Survey of Stellar Families: Multiplicity of Solar-type Stars | journal=The Astrophysical Journal Supplement | volume=190 | issue=1 | pages=1–42 |date=September 2010 | doi=10.1088/0067-0049/190/1/1 | bibcode=2010ApJS..190....1R |arxiv = 1007.0414 | s2cid=368553 }} For the adopted physical separation, see Table 11 in the appendix.</ref>
<ref name=Harada2025>{{citation |last1=Harada |first1=Caleb K. |last2=Dressing |first2=Courtney D. |last3=Turtelboom |first3=Emma V. |last4=Kane |first4=Stephen R. |last5=Blunt |first5=Sarah |last6=Dietrich |first6=Jamie |last7=Hinkel |first7=Natalie R. |last8=Li |first8=Zhexing |last9=Mamajek |first9=Eric |date=2025-09-23 |title=SPORES-HWO. II. Companion Mass Limits and Updated Planet Properties for 120 Future Exoplanet Imaging Targets from 35 Years of Precise Doppler Monitoring |journal=[[The Astronomical Journal]] |arxiv=2409.10679 }}</ref>
<ref name="Mugrauer2019">{{citation|last1=Mugrauer |first1=M. |date=December 2019 |title=Search for stellar companions of exoplanet host stars by exploring the second ESA-Gaia data release |journal=[[Monthly Notices of the Royal Astronomical Society]] |volume=490 |issue=4 |pages=5088–5102 |doi=10.1093/mnras/stz2673 |doi-access=free |bibcode=2019MNRAS.490.5088M}}</ref>
<ref name=Nissen2020>{{Citation |last1=Nissen |first1=P. E. |last2=Christensen-Dalsgaard |first2=J. |last3=Mosumgaard |first3=J. R. |last4=Silva Aguirre |first4=V. |last5=Spitoni |first5=E. |last6=Verma |first6=K. |date=August 2020 |title=High-precision abundances of elements in solar-type stars: Evidence of two distinct sequences in abundance-age relations |journal=Astronomy & Astrophysics |volume=640 |pages=A81 |doi=10.1051/0004-6361/202038300 |issn=0004-6361|arxiv=2006.06013 |bibcode=2020A&A...640A..81N }}</ref>
<ref name=Harada2024>{{citation | title=Setting the Stage for the Search for Life with the Habitable Worlds Observatory: Properties of 164 Promising Planet-survey Targets | last1=Harada | first1=Caleb K. | last2=Dressing | first2=Courtney D. | last3=Kane | first3=Stephen R. | last4=Ardestani | first4=Bahareh Adami | journal=The Astrophysical Journal Supplement Series | volume=272 | issue=2 | at=id. 30 | date=June 2024 | doi=10.3847/1538-4365/ad3e81 | doi-access=free | arxiv=2401.03047 | bibcode=2024ApJS..272...30H | display-authors=1 }}</ref>
<ref name=Casali2020>{{citation |last1=Casali |first1=G. |last2=Spina |first2=L. |last3=Magrini |first3=L. |last4=Karakas |first4=A. I. |last5=Kobayashi |first5=C. |last6=Casey |first6=A. R. |last7=Feltzing |first7=S. |last8=Swaelmen |first8=M. Van der |last9=Tsantaki |first9=M. |last10=Jofré |first10=P. |last11=Bragaglia |first11=A. |last12=Feuillet |first12=D. |last13=Bensby |first13=T. |last14=Biazzo |first14=K. |last15=Gonneau |first15=A. |date=2020-07-01 |title=The Gaia-ESO survey: the non-universality of the age–chemical-clocks–metallicity relations in the Galactic disc |journal=Astronomy & Astrophysics |language=en |volume=639 |pages=A127 |doi=10.1051/0004-6361/202038055 |issn=0004-6361|arxiv=2006.05763 |bibcode=2020A&A...639A.127C }}</ref>
<ref name=Figueira2025>{{Citation |last1=Figueira |first1=P. |last2=Faria |first2=J. P. |last3=Silva |first3=A. M. |last4=Castro-González |first4=A. |last5=Silva |first5=J. Gomes da |last6=Sousa |first6=S. G. |last7=Bossini |first7=D. |last8=Zapatero-Osorio |first8=M. R. |last9=Balsalobre-Ruza |first9=O. |title=A comprehensive study on radial velocity signals using ESPRESSO: Pushing precision to the 10 cm/s level |date=2025-07-10 |arxiv=2507.07514 |journal=[[Astronomy and Astrophysics]] |volume=700 |pages=A174 |doi=10.1051/0004-6361/202553869 |bibcode=2025A&A...700A.174F }}</ref>
<ref name=aaa68_1_27>{{citation | last1=Kovacs | first1=N. | last2=Foy | first2=R. | title=A detailed analysis of three stars in the Eggen's Epsilon INDI moving group | journal=Astronomy and Astrophysics | year=1978 | volume=68 | issue=1–2 | pages=27–31 | bibcode=1978A&A....68...27K }}</ref>
<ref name=aaa493_3_1099>{{citation | last1=Schröder | first1=C. | last2=Reiners | first2=Ansgar | last3=Schmitt | first3=Jürgen H. M. M. | title=Ca II HK emission in rapidly rotating stars. Evidence for an onset of the solar-type dynamo | journal=Astronomy and Astrophysics | volume=493 | issue=3 | pages=1099–1107 | date=January 2009 | doi=10.1051/0004-6361:200810377 | bibcode=2009A&A...493.1099S | doi-access=free }}</ref>
<ref name=SIMBAD>{{cite simbad | title=HD 102365 | access-date=2011-10-11 }}</ref>
<ref name=Gould1879>{{citation | url=http://vizier.u-strasbg.fr/viz-bin/VizieR?-source=V%2F135%2Fcatalog | last=Gould | first=Benjamin Apthorp | date=1879 | title=Uranometria Argentina catalog of bright southern stars | journal=Resultados del Observatorio Nacional Argentino en Cordoba | volume=1 | publication-place=Buenos Aires | bibcode=1879RNAO....1.....G | access-date=2012-05-08 }}</ref>
<ref name=aaa501_3_941>{{citation | last1=Holmberg | first1=J. | last2=Nordström | first2=B. | last3=Andersen | first3=J. | title=The Geneva-Copenhagen survey of the solar neighbourhood. III. Improved distances, ages, and kinematics | journal=Astronomy and Astrophysics | volume=501 | issue=3 | pages=941–947 |date=July 2009 | doi=10.1051/0004-6361/200811191 | bibcode=2009A&A...501..941H |arxiv = 0811.3982 | s2cid=118577511 }}</ref>
<ref name=metal>For a metallicity of [Fe/H] = −0.28 dex, the proportion of metals is given by 10<sup>−0.28</sup>, or 52%.</ref>
<ref name=rmaa28_1_43>{{citation | display-authors=1 | last1=Poveda | first1=A. | last2=Herrera | first2=M. A. | last3=Allen | first3=C. | last4=Cordero | first4=G. | last5=Lavalley | first5=C. | title=Statistical studies of visual double and multiple stars. II. A catalogue of nearby wide binary and multiple systems | journal=Revista Mexicana de Astronomía y Astrofísica | volume=28 | issue=1 | pages=43–89 |date=April 1994 | bibcode=1994RMxAA..28...43P }}</ref>
<ref name=gliese1969>{{citation | last1=Gliese | first1=W. | contribution=Catalogue of Nearby Stars. Edition 1969 | title=Veröffentlichungen des Astronomischen Rechen-Instituts Heidelberg | issue=22 | location=Karlsruhe | year=1969 | volume=22 | page=1 | bibcode=1969VeARI..22....1G }}</ref>
<ref name=apj727_103>{{citation | display-authors=1 | last1=Tinney | first1=C. G. | last2=Butler | first2=R. Paul | last3=Jones | first3=Hugh R. A. | last4=Wittenmyer | first4=Robert A. | last5=O'Toole | first5=Simon | last6=Bailey | first6=Jeremy | last7=Carter | first7=Brad D. | title=The Anglo-Australian Planet Search. XX. A Solitary Ice-giant Planet Orbiting HD 102365 | journal=The Astrophysical Journal | year=2011 | volume=727 | issue=2 | page=103 | doi=10.1088/0004-637X/727/2/103 | bibcode=2011ApJ...727..103T | s2cid=54984338 }}</ref>
<ref name=apj652_2_1674>{{citation | display-authors=1 | last1=Beichman | first1=C. A. | last2=Bryden | first2=G. | last3=Stapelfeldt | first3=K. R. | last4=Gautier | first4=T. N. | last5=Grogan | first5=K. | last6=Shao | first6=M. | last7=Velusamy | first7=T. | last8=Lawler | first8=S. M. | last9=Blaylock | first9=M. | title=New Debris Disks around Nearby Main-Sequence Stars: Impact on the Direct Detection of Planets | journal=The Astrophysical Journal | volume=652 | issue=2 | pages=1674–1693 |date=December 2006 | doi=10.1086/508449 | bibcode=2006ApJ...652.1674B |arxiv = astro-ph/0611682 | s2cid=14207148 }}</ref>
<ref name="Zechmeister2013">{{citation |last1=Zechmeister |first1=M. |last2=Kürster |first2=M. |display-authors=etal |date=April 2013 |title=The planet search programme at the ESO CES and HARPS. IV. The search for Jupiter analogues around solar-like stars |journal=[[Astronomy & Astrophysics]] |volume=552 |issue= |pages=A78 |doi=10.1051/0004-6361/201116551 |arxiv=1211.7263 |bibcode=2013A&A...552A..78Z|s2cid=53694238 }}</ref>
<ref name="Laliotis2023">{{citation |last1=Laliotis |first1=Katherine |last2=Burt |first2=Jennifer A. |display-authors=etal |date=February 2023 |title=Doppler Constraints on Planetary Companions to Nearby Sun-like Stars: An Archival Radial Velocity Survey of Southern Targets for Proposed NASA Direct Imaging Missions |journal=[[The Astronomical Journal]] |volume= 165|issue= 4|page=176 |doi= 10.3847/1538-3881/acc067|arxiv=2302.10310 |bibcode=2023AJ....165..176L |doi-access=free }}</ref> </references>
==External links== * {{citation | title=HR 4523 AB | publisher=SolStation | url=http://www.solstation.com/stars/hr4523ab.htm | archive-url=https://web.archive.org/web/20010425205359/http://solstation.com/stars/hr4523ab.htm | url-status=dead | archive-date=April 25, 2001 | access-date=2011-10-11 }}
{{Stars of Centaurus}} <!-- Properties -->
[[Category:G-type main-sequence stars]] [[Category:Solar analogs|HR, 4523]] [[Category:Hypothetical planetary systems]] [[Category:M-type main-sequence stars]] [[Category:Binary stars]] <!-- Catalogues --> [[Category:Centaurus]] [[Category:Durchmusterung objects|CD-39 07301]] [[Category:Gliese and GJ objects|0442]] [[Category:Gould objects|Centauri, 66]] [[Category:Henry Draper Catalogue objects|102365]] [[Category:Hipparcos objects|057433]] [[Category:Bright Star Catalogue objects|4523]]