HD 121056

{{Short description|Star in the constellation Centaurus}} {{Starbox begin}} {{Starbox observe | epoch = J2000 | constell = [[Centaurus]]<ref name=xhip/> | ra = {{RA|13|53|52.06131}}<ref name="GaiaDR3"/> | dec = {{DEC|−35|18|51.6918}}<ref name="GaiaDR3"/> | appmag_v = 6.17<ref name=Hojjatpanah2019/> }} {{Starbox character | type = [[red giant branch]]<ref name="GaiaDR3"/> | class = K0 III<ref name=houk1999/> | b-v = 1.01<ref name=Jones2014/> | variable = }} {{Starbox astrometry | radial_v = {{val|5.60|0.13}}<ref name="GaiaDR3"/> | prop_mo_ra = {{val|−295.304}} | prop_mo_dec = {{val|−68.458}} | pm_footnote = <ref name="GaiaDR3"/> | parallax = 15.6261 | p_error = 0.0418 | parallax_footnote = <ref name="GaiaDR3"/> | absmag_v = +2.08<ref name=xhip/> }} {{Starbox detail | source = | mass = {{val|1.394|0.052}}<ref name=Lin2024/> | radius = {{val|5.948|0.077}}<ref name=Lin2024/> | temperature = {{val|4,867|49|fmt=commas}}<ref name=Hojjatpanah2019/> | luminosity = {{val|18.2|2.0|1.8}}<ref name=Lin2024/> | gravity = {{val|3.034|0.005}}<ref name=Lin2024/> | metal_fe = {{val|0.020|0.031}}<ref name=Hojjatpanah2019/> | metal = [Mg/H] {{val|0.286|0.05}} dex<ref name=Hojjatpanah2019/> | rotation = | rotational_velocity = {{val|2.38|0.51}}<ref name=Hojjatpanah2019/> | age_gyr = {{val|5.46}}<ref name=soto2021/> }} {{Starbox catalog | names = {{odlist | CD=−34 9223 | 2MASS=J13535209-3518517 | TYC=7287-1874-1 | HD=121056 | HIP=67851 | HR=5224 | GJ=532.1 }}<ref name=SIMBAD/> }} {{Starbox reference | Simbad = HD+121056 | NSTED = HIP-67851 }} {{Starbox end}}

'''HD 121056''', or '''HIP 67851''', is an aging [[giant star]] with a pair of orbiting [[exoplanet]]s located in the southern [[constellation]] of [[Centaurus (constellation)|Centaurus]]. This star is dimly visible to the naked eye with an [[apparent visual magnitude]] of 6.17.<ref name=Hojjatpanah2019/> It is located at a distance of 209 [[light-year]]s from the Sun, based on [[stellar parallax|parallax]] measurements, and is drifting further away with a [[radial velocity]] of 5.6 km/s.<ref name="GaiaDR3"/>

The [[stellar spectrum|spectrum]] of HD 121056 presents as an [[stellar evolution|evolved]] [[K-type star|K-type]] [[giant star]] with a [[stellar classification]] of K0 III.<ref name=Wittenmyer2014/> It is presently ascending the [[red-giant branch]], having exhausted the supply of hydrogen at its [[stellar core|core]].<ref name=Jones2014/> The star is about 5.5<ref name=soto2021/> billion years old and is spinning with a [[projected rotational velocity]] of 2.4 km/s. HD 121056's concentration of heavy elements is similar to the [[Sun]], with a [[metallicity]] Fe/H index of 0.020{{±|0.031}}, although the star is enriched in lighter rock-forming elements like magnesium and aluminum.<ref name=Hojjatpanah2019/> It has 1.6<ref name=Sousa_et_al_2018/> times the mass of the Sun and has expanded to 5.72 times the Sun's radius.<ref name=soto2021/> The star is radiating 15.8<ref name=soto2021/> times the luminosity of the Sun from its enlarged [[photosphere]] at an [[effective temperature]] of 4,867 K.<ref name=Hojjatpanah2019/>

==Planetary system== In 2014, two planets orbiting HD 121056 were discovered by the [[radial velocity method]],<ref name=Jones2014/> and were confirmed a few months later.<ref name=Wittenmyer2014/> The orbits of these planets are stable on astronomical timescales,<ref name=Kane_et_al_2019/> although the periods are not in [[orbital resonance]].<ref name=Saillenfest_et_al_2019/> In 2022, the inclination and true mass of HD 121056 c were measured via [[astrometry]], indicating a nearly edge-on orbit.<ref name="Feng2022"/> Subsequent studies have provided further updates to the planetary parameters.<ref name=Lin2024/><ref name=Fontanet2025/>

The planetary system configuration is favorable for direct imaging of exoplanets in the near future, being included in the top ten easiest targets in 2018.<ref name=Martinache_et_al_2018/>

{{OrbitboxPlanet begin | name = HD 121056 | table_ref = <ref name=Fontanet2025/>{{efn|Most parameters are taken from the most recent study of the system, Fontanet ''et al.'' 2025. This does not incorporate astrometry, hence the mass of planet c is technically a [[minimum mass]], but since the inclination measured by Feng ''et al.'' 2022 is nearly edge-on, the true mass is about the same as this value.}} }} {{OrbitboxPlanet | exoplanet = b | mass = {{val|1.15|0.04|p=≥}} | radius = | semimajor = {{val|0.42|0.0002}} | period = {{val|89.23|0.06}} | eccentricity = {{val|0.13|0.04}} | inclination = }} {{OrbitboxPlanet | exoplanet = c | mass = {{val|4.97|0.22|0.21}} | radius = | semimajor = {{val|4.55|0.05}} | period = {{val|3128.41|52.09|47.13|fmt=commas}} | eccentricity = {{val|0.30|0.03}} | inclination = {{val|89.86|28.38|24.73}}<ref name="Feng2022"/> }} {{Orbitbox end}}

==Notes== {{Notelist}}

==References== {{Reflist|refs=

<ref name=SIMBAD>{{cite simbad|title=HD 121056|accessdate=2021-05-13}}</ref>

<ref name=houk1999>{{cite journal | title=Michigan catalogue of two-dimensional spectral types for the HD Stars | last1=Houk | first1=N. | last2=Swift | first2=C. | journal=Michigan Spectral Survey | volume=5 | year=1999 | bibcode=1999MSS...C05....0H }}</ref>

<ref name=Jones2014>{{cite journal | title=A planetary system and a highly eccentric brown dwarf around the giant stars HIP 67851 and HIP 97233 | display-authors=1 | last1=Jones | first1=M. I. | last2=Jenkins | first2=J. S. | last3=Rojo | first3=P. | last4=Melo | first4=C. H. F. | last5=Bluhm | first5=P. | journal=Astronomy & Astrophysics | volume=573 | pages=A3 | year=2015 | arxiv=1409.7429 | doi=10.1051/0004-6361/201424771 | bibcode=2015A&A...573A...3J | s2cid=53638707 }}</ref>

<ref name=Sousa_et_al_2018>{{cite journal | title=SWEET-Cat updated | display-authors=1 | last1=Sousa | first1=S. G. | last2=Adibekyan | first2=V. | last3=Delgado-Mena | first3=E. | last4=Santos | first4=N. C. | last5=Andreasen | first5=D. T. | last6=Ferreira | first6=A. C. S. | last7=Tsantaki | first7=M. | last8=Barros | first8=S. C. C. | last9=Demangeon | first9=O. | last10=Israelian | first10=G. | last11=Faria | first11=J. P. | last12=Figueira | first12=P. | last13=Mortier | first13=A. | last14=Brandão | first14=I. | last15=Montalto | first15=M. | last16=Rojas-Ayala | first16=B. | last17=Santerne | first17=A. | journal=Astronomy & Astrophysics | volume=620 | pages=A58 | year=2018 | arxiv=1810.08108 | doi=10.1051/0004-6361/201833350 | bibcode=2018A&A...620A..58S | s2cid=119374557 }}</ref>

<ref name=Lin2024>{{Cite journal |last=Lin |first=Wen-Xu |last2=Qian |first2=Sheng-Bang |last3=Zhu |first3=Li-Ying |last4=Liao |first4=Wen-Ping |last5=Li |first5=Fu-Xing |date=2024-07-01 |title=Using Asteroseismology to Calibrate the Physical Parameters of Confirmed Exoplanets and Their Evolved Host Stars |journal=The Astronomical Journal |volume=168 |issue=1 |pages=27 |doi=10.3847/1538-3881/ad4ffc |doi-access=free |arxiv=2405.15162 |bibcode=2024AJ....168...27L |issn=0004-6256}}</ref>

<ref name=soto2021>{{cite journal | title=SPECIES. II. Stellar parameters of the EXPRESS giant star sample | display-authors=1 | last1=Soto | first1=M. G. | last2=Jones | first2=M. I. | last3=Jenkins | first3=J. S. | journal=Astronomy and Astrophysics | year=2021 | volume=647 | pages=A157 | doi=10.1051/0004-6361/202039357 |arxiv=2009.03371 | bibcode=2021A&A...647A.157S | s2cid=221534230 }}</ref>

<ref name=Hojjatpanah2019>{{cite journal | title=Catalog for the ESPRESSO blind radial velocity exoplanet survey | last1=Hojjatpanah | first1=S. | last2=Figueira | first2=P. | last3=Santos | first3=N. C. | last4=Adibekyan | first4=V. | last5=Sousa | first5=S. G. | last6=Delgado-Mena | first6=E. | last7=Alibert | first7=Y. | last8=Cristiani | first8=S. | last9=González Hernández | first9=J. I. |last10=Lanza | first10=A. F. | last11=Di Marcantonio | first11=P. | last12=Martins | first12=J. H. C. | last13=Micela | first13=G. | last14=Molaro | first14=P. | last15=Neves | first15=V. | last16=Oshagh | first16=M. | last17=Pepe | first17=F. | last18=Poretti | first18=E. | last19=Rojas-Ayala | first19=B. | last20=Rebolo | first20=R. | last21=Suárez Mascareño | first21=A. | last22=Zapatero Osorio | first22=M. R. | display-authors=1 | journal=Astronomy & Astrophysics | volume=629 | pages=A80 | year=2019 | arxiv=1908.04627 | doi=10.1051/0004-6361/201834729 | bibcode=2019A&A...629A..80H | s2cid=199552090 }}</ref>

<ref name=Wittenmyer2014>{{cite journal | title=The Pan-Pacific Planet Search. II. Confirmation of a Two-planet System around HD 121056 | last1=Wittenmyer | first1=Robert A. | last2=Wang | first2=Liang | last3=Liu | first3=Fan | last4=Horner | first4=Jonathan | last5=Endl | first5=Michael | last6=Johnson | first6=John Asher | last7=Tinney | first7=C. G. | last8=Carter | first8=B. D. | display-authors=1 | journal=The Astrophysical Journal | volume=800 | issue=1 | page=74 | year=2015 | arxiv=1412.6889 | doi=10.1088/0004-637X/800/1/74 | bibcode=2015ApJ...800...74W |s2cid=53684180 }}</ref>

<ref name=Kane_et_al_2019>{{cite journal | display-authors=1 | title=Predicting multiple planet stability and habitable zone companions in the TESS era | last1=Kane | first1=Stephen R. | last2=Horner | first2=Jonathan | last3=Maddison | first3=Sarah T. | last4=Agnew | first4=Matthew T. | journal=Monthly Notices of the Royal Astronomical Society | volume=485 | issue=4 | pages=4703–4725 | year=2019 | doi=10.1093/mnras/stz345 | doi-access=free | arxiv=1901.11297 | bibcode=2019MNRAS.485.4703A }}</ref>

<ref name=Saillenfest_et_al_2019>{{cite journal | title=Secular spin-axis dynamics of exoplanets | display-authors=1 | last1=Saillenfest | first1=M. | last2=Laskar | first2=J. | last3=Boué | first3=G. | journal=Astronomy & Astrophysics | volume=623 | pages=A4 | year=2019 | arxiv=1901.02831 | doi=10.1051/0004-6361/201834344 | bibcode=2019A&A...623A...4S | s2cid=119073661 }}</ref>

<ref name="Feng2022">{{cite journal | title=3D Selection of 167 Substellar Companions to Nearby Stars | last1=Feng | first1=Fabo | last2=Butler | first2=R. Paul | display-authors=etal | journal=[[The Astrophysical Journal Supplement Series]] | volume=262 | issue=21 | page=21 | date=August 2022 | doi=10.3847/1538-4365/ac7e57 | arxiv=2208.12720 | doi-access=free | bibcode=2022ApJS..262...21F | s2cid=251864022 }}</ref>

<ref name=Martinache_et_al_2018>{{cite journal | title=Kernel-nulling for a robust direct interferometric detection of extrasolar planets | last1=Martinache | first1=Frantz | last2=Ireland | first2=Michael J. | journal=Astronomy & Astrophysics | volume=619 | pages=A87 | year=2018 | doi=10.1051/0004-6361/201832847 | arxiv=1802.06252 | bibcode=2018A&A...619A..87M | s2cid=118882482 }}</ref>

<ref name=Fontanet2025>{{cite journal |last1=Fontanet |first1=E. |last2=Udry |first2=S. |display-authors=etal |date=May 2025 |title=CORALIE radial-velocity search for companions around evolved stars (CASCADES) IV: New planetary systems around HD 87816, HD 94890, and HD 102888 and an update on HD 121056 |journal=[[Astronomy & Astrophysics]] |volume= |issue= |pages= |doi= |arxiv=2505.14317}}</ref>

}}

{{DEFAULTSORT:HD 121056}} [[Category:K-type giants]] [[Category:Planetary systems with two confirmed planets]]  [[Category:Centaurus]] [[Category:Bright Star Catalogue objects|5224]] [[Category:Durchmusterung objects|CD-34 9223]] [[Category:Gliese and GJ objects|0532.1]] [[Category:Hipparcos objects|067851]] [[Category:Henry Draper Catalogue objects|121056]]