# HD 121056

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Star in the constellation Centaurus

HD 121056 Observation data Epoch J2000 Equinox J2000 Constellation Centaurus[1] Right ascension 13h 53m 52.06131s[2] Declination −35° 18′ 51.6918″[2] Apparent magnitude (V) 6.17[3] Characteristics Evolutionary stage red giant branch[2] Spectral type K0 III[4] B−V color index 1.01[5] Astrometry Radial velocity (Rv) 5.60±0.13[2] km/s Proper motion (μ) RA: −295.304 mas/yr[2] Dec.: −68.458 mas/yr[2] Parallax (π) 15.6261±0.0418 mas[2] Distance 208.7 ± 0.6 ly (64.0 ± 0.2 pc) Absolute magnitude (MV) +2.08[1] Details Mass 1.394±0.052[6] M☉ Radius 5.948±0.077[6] R☉ Luminosity 18.2+2.0 −1.8[6] L☉ Surface gravity (log g) 3.034±0.005[6] cgs Temperature 4,867±49[3] K Metallicity [Mg/H] 0.286±0.05 dex[3] Metallicity [Fe/H] 0.020±0.031[3] dex Rotational velocity (v sin i) 2.38±0.51[3] km/s Age 5.46[7] Gyr Other designations CD−34 9223, GJ 532.1, HD 121056, HIP 67851, HR 5224, TYC 7287-1874-1, 2MASS J13535209-3518517[8] Database references SIMBAD data Exoplanet Archive data

**HD 121056**, or **HIP 67851**, is an aging [giant star](/source/Giant_star) with a pair of orbiting [exoplanets](/source/Exoplanet) located in the southern [constellation](/source/Constellation) of [Centaurus](/source/Centaurus_(constellation)). This star is dimly visible to the naked eye with an [apparent visual magnitude](/source/Apparent_visual_magnitude) of 6.17.[3] It is located at a distance of 209 [light-years](/source/Light-year) from the Sun, based on [parallax](/source/Stellar_parallax) measurements, and is drifting further away with a [radial velocity](/source/Radial_velocity) of 5.6 km/s.[2]

The [spectrum](/source/Stellar_spectrum) of HD 121056 presents as an [evolved](/source/Stellar_evolution) [K-type](/source/K-type_star) [giant star](/source/Giant_star) with a [stellar classification](/source/Stellar_classification) of K0 III.[9] It is presently ascending the [red-giant branch](/source/Red-giant_branch), having exhausted the supply of hydrogen at its [core](/source/Stellar_core).[5] The star is about 5.5[7] billion years old and is spinning with a [projected rotational velocity](/source/Projected_rotational_velocity) of 2.4 km/s. HD 121056's concentration of heavy elements is similar to the [Sun](/source/Sun), with a [metallicity](/source/Metallicity) Fe/H index of 0.020±0.031, although the star is enriched in lighter rock-forming elements like magnesium and aluminum.[3] It has 1.6[10] times the mass of the Sun and has expanded to 5.72 times the Sun's radius.[7] The star is radiating 15.8[7] times the luminosity of the Sun from its enlarged [photosphere](/source/Photosphere) at an [effective temperature](/source/Effective_temperature) of 4,867 K.[3]

## Planetary system

In 2014, two planets orbiting HD 121056 were discovered by the [radial velocity method](/source/Radial_velocity_method),[5] and were confirmed a few months later.[9] The orbits of these planets are stable on astronomical timescales,[11] although the periods are not in [orbital resonance](/source/Orbital_resonance).[12] In 2022, the inclination and true mass of HD 121056 c were measured via [astrometry](/source/Astrometry), indicating a nearly edge-on orbit.[13] Subsequent studies have provided further updates to the planetary parameters.[6][14]

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.[15]

The HD 121056 planetary system[14][a] Companion (in order from star) Mass Semimajor axis (AU) Orbital period (days) Eccentricity Inclination (°) Radius b ≥1.15±0.04 MJ 0.42±0.0002 89.23±0.06 0.13±0.04 — — c 4.97+0.22 −0.21 MJ 4.55±0.05 3,128.41+52.09 −47.13 0.30±0.03 89.86+28.38 −24.73[13] —

## Notes

1. **[^](#cite_ref-16)** 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](/source/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.

## References

1. ^ [***a***](#cite_ref-xhip_1-0) [***b***](#cite_ref-xhip_1-1) Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". *[Astronomy Letters](/source/Astronomy_Letters)*. **38** (5): 331. [arXiv](/source/ArXiv_(identifier)):[1108.4971](https://arxiv.org/abs/1108.4971). [Bibcode](/source/Bibcode_(identifier)):[2012AstL...38..331A](https://ui.adsabs.harvard.edu/abs/2012AstL...38..331A). [doi](/source/Doi_(identifier)):[10.1134/S1063773712050015](https://doi.org/10.1134%2FS1063773712050015). [XHIP record for this object](https://vizier.cds.unistra.fr/viz-bin/VizieR-4?-ref=VIZ681510a8389ecb&-out.src=V%2F137D%2FXHIP&-nav=cat%3AV%2F137D%26tab%3A{V%2F137D%2FXHIP}%26key%3Asource%3DV%2F137D%2FXHIP%26HTTPPRM%3A&-source=V%2F137D%2FXHIP&-out=HIP&HIP=67851&-out=Comp&-out=Gr&-out=RAJ2000&-out=DEJ2000&-out=Dist&-out=X&-out=Y&-out=Z&-out=SpType&-out=Simbad&-out=Hpmag&-out=Lum&-out=Cst) at [VizieR](/source/VizieR).

1. ^ [***a***](#cite_ref-GaiaDR3_2-0) [***b***](#cite_ref-GaiaDR3_2-1) [***c***](#cite_ref-GaiaDR3_2-2) [***d***](#cite_ref-GaiaDR3_2-3) [***e***](#cite_ref-GaiaDR3_2-4) [***f***](#cite_ref-GaiaDR3_2-5) [***g***](#cite_ref-GaiaDR3_2-6) Vallenari, A.; et al. (Gaia collaboration) (2023). ["*Gaia* Data Release 3. Summary of the content and survey properties"](https://doi.org/10.1051%2F0004-6361%2F202243940). *Astronomy and Astrophysics*. **674**: A1. [arXiv](/source/ArXiv_(identifier)):[2208.00211](https://arxiv.org/abs/2208.00211). [Bibcode](/source/Bibcode_(identifier)):[2023A&A...674A...1G](https://ui.adsabs.harvard.edu/abs/2023A&A...674A...1G). [doi](/source/Doi_(identifier)):[10.1051/0004-6361/202243940](https://doi.org/10.1051%2F0004-6361%2F202243940). [S2CID](/source/S2CID_(identifier)) [244398875](https://api.semanticscholar.org/CorpusID:244398875). [Gaia DR3 record for this source](https://vizier.cds.unistra.fr/viz-bin/VizieR-4?-source=+I%2F355&-from=nav&-nav=cat%3AI%2F355%26tab%3A%7BI%2F355%2Fgaiadr3%7D%26key%3Asource%3D1355%2Fgaiadr3%26HTTPPRM%3A%26-out.add%3D.%26Source%3D%3D%3D6169943210465504384%26-go+%25%23Sesame%23%25%26) at [VizieR](/source/VizieR).

1. ^ [***a***](#cite_ref-Hojjatpanah2019_3-0) [***b***](#cite_ref-Hojjatpanah2019_3-1) [***c***](#cite_ref-Hojjatpanah2019_3-2) [***d***](#cite_ref-Hojjatpanah2019_3-3) [***e***](#cite_ref-Hojjatpanah2019_3-4) [***f***](#cite_ref-Hojjatpanah2019_3-5) [***g***](#cite_ref-Hojjatpanah2019_3-6) [***h***](#cite_ref-Hojjatpanah2019_3-7) Hojjatpanah, S.; et al. (2019). "Catalog for the ESPRESSO blind radial velocity exoplanet survey". *Astronomy & Astrophysics*. **629**: A80. [arXiv](/source/ArXiv_(identifier)):[1908.04627](https://arxiv.org/abs/1908.04627). [Bibcode](/source/Bibcode_(identifier)):[2019A&A...629A..80H](https://ui.adsabs.harvard.edu/abs/2019A&A...629A..80H). [doi](/source/Doi_(identifier)):[10.1051/0004-6361/201834729](https://doi.org/10.1051%2F0004-6361%2F201834729). [S2CID](/source/S2CID_(identifier)) [199552090](https://api.semanticscholar.org/CorpusID:199552090).

1. **[^](#cite_ref-houk1999_4-0)** Houk, N.; Swift, C. (1999). "Michigan catalogue of two-dimensional spectral types for the HD Stars". *Michigan Spectral Survey*. **5**. [Bibcode](/source/Bibcode_(identifier)):[1999MSS...C05....0H](https://ui.adsabs.harvard.edu/abs/1999MSS...C05....0H).

1. ^ [***a***](#cite_ref-Jones2014_5-0) [***b***](#cite_ref-Jones2014_5-1) [***c***](#cite_ref-Jones2014_5-2) Jones, M. I.; et al. (2015). "A planetary system and a highly eccentric brown dwarf around the giant stars HIP 67851 and HIP 97233". *Astronomy & Astrophysics*. **573**: A3. [arXiv](/source/ArXiv_(identifier)):[1409.7429](https://arxiv.org/abs/1409.7429). [Bibcode](/source/Bibcode_(identifier)):[2015A&A...573A...3J](https://ui.adsabs.harvard.edu/abs/2015A&A...573A...3J). [doi](/source/Doi_(identifier)):[10.1051/0004-6361/201424771](https://doi.org/10.1051%2F0004-6361%2F201424771). [S2CID](/source/S2CID_(identifier)) [53638707](https://api.semanticscholar.org/CorpusID:53638707).

1. ^ [***a***](#cite_ref-Lin2024_6-0) [***b***](#cite_ref-Lin2024_6-1) [***c***](#cite_ref-Lin2024_6-2) [***d***](#cite_ref-Lin2024_6-3) [***e***](#cite_ref-Lin2024_6-4) Lin, Wen-Xu; Qian, Sheng-Bang; Zhu, Li-Ying; Liao, Wen-Ping; Li, Fu-Xing (2024-07-01). ["Using Asteroseismology to Calibrate the Physical Parameters of Confirmed Exoplanets and Their Evolved Host Stars"](https://doi.org/10.3847%2F1538-3881%2Fad4ffc). *The Astronomical Journal*. **168** (1): 27. [arXiv](/source/ArXiv_(identifier)):[2405.15162](https://arxiv.org/abs/2405.15162). [Bibcode](/source/Bibcode_(identifier)):[2024AJ....168...27L](https://ui.adsabs.harvard.edu/abs/2024AJ....168...27L). [doi](/source/Doi_(identifier)):[10.3847/1538-3881/ad4ffc](https://doi.org/10.3847%2F1538-3881%2Fad4ffc). [ISSN](/source/ISSN_(identifier)) [0004-6256](https://search.worldcat.org/issn/0004-6256).

1. ^ [***a***](#cite_ref-soto2021_7-0) [***b***](#cite_ref-soto2021_7-1) [***c***](#cite_ref-soto2021_7-2) [***d***](#cite_ref-soto2021_7-3) Soto, M. G.; et al. (2021). "SPECIES. II. Stellar parameters of the EXPRESS giant star sample". *Astronomy and Astrophysics*. **647**: A157. [arXiv](/source/ArXiv_(identifier)):[2009.03371](https://arxiv.org/abs/2009.03371). [Bibcode](/source/Bibcode_(identifier)):[2021A&A...647A.157S](https://ui.adsabs.harvard.edu/abs/2021A&A...647A.157S). [doi](/source/Doi_(identifier)):[10.1051/0004-6361/202039357](https://doi.org/10.1051%2F0004-6361%2F202039357). [S2CID](/source/S2CID_(identifier)) [221534230](https://api.semanticscholar.org/CorpusID:221534230).

1. **[^](#cite_ref-SIMBAD_8-0)** ["HD 121056"](http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=HD+121056). *[SIMBAD](/source/SIMBAD)*. [Centre de données astronomiques de Strasbourg](/source/Centre_de_donn%C3%A9es_astronomiques_de_Strasbourg). Retrieved 2021-05-13.

1. ^ [***a***](#cite_ref-Wittenmyer2014_9-0) [***b***](#cite_ref-Wittenmyer2014_9-1) Wittenmyer, Robert A.; et al. (2015). "The Pan-Pacific Planet Search. II. Confirmation of a Two-planet System around HD 121056". *The Astrophysical Journal*. **800** (1): 74. [arXiv](/source/ArXiv_(identifier)):[1412.6889](https://arxiv.org/abs/1412.6889). [Bibcode](/source/Bibcode_(identifier)):[2015ApJ...800...74W](https://ui.adsabs.harvard.edu/abs/2015ApJ...800...74W). [doi](/source/Doi_(identifier)):[10.1088/0004-637X/800/1/74](https://doi.org/10.1088%2F0004-637X%2F800%2F1%2F74). [S2CID](/source/S2CID_(identifier)) [53684180](https://api.semanticscholar.org/CorpusID:53684180).

1. **[^](#cite_ref-Sousa_et_al_2018_10-0)** Sousa, S. G.; et al. (2018). "SWEET-Cat updated". *Astronomy & Astrophysics*. **620**: A58. [arXiv](/source/ArXiv_(identifier)):[1810.08108](https://arxiv.org/abs/1810.08108). [Bibcode](/source/Bibcode_(identifier)):[2018A&A...620A..58S](https://ui.adsabs.harvard.edu/abs/2018A&A...620A..58S). [doi](/source/Doi_(identifier)):[10.1051/0004-6361/201833350](https://doi.org/10.1051%2F0004-6361%2F201833350). [S2CID](/source/S2CID_(identifier)) [119374557](https://api.semanticscholar.org/CorpusID:119374557).

1. **[^](#cite_ref-Kane_et_al_2019_11-0)** Kane, Stephen R.; et al. (2019). ["Predicting multiple planet stability and habitable zone companions in the TESS era"](https://doi.org/10.1093%2Fmnras%2Fstz345). *Monthly Notices of the Royal Astronomical Society*. **485** (4): 4703–4725. [arXiv](/source/ArXiv_(identifier)):[1901.11297](https://arxiv.org/abs/1901.11297). [Bibcode](/source/Bibcode_(identifier)):[2019MNRAS.485.4703A](https://ui.adsabs.harvard.edu/abs/2019MNRAS.485.4703A). [doi](/source/Doi_(identifier)):[10.1093/mnras/stz345](https://doi.org/10.1093%2Fmnras%2Fstz345).

1. **[^](#cite_ref-Saillenfest_et_al_2019_12-0)** Saillenfest, M.; et al. (2019). "Secular spin-axis dynamics of exoplanets". *Astronomy & Astrophysics*. **623**: A4. [arXiv](/source/ArXiv_(identifier)):[1901.02831](https://arxiv.org/abs/1901.02831). [Bibcode](/source/Bibcode_(identifier)):[2019A&A...623A...4S](https://ui.adsabs.harvard.edu/abs/2019A&A...623A...4S). [doi](/source/Doi_(identifier)):[10.1051/0004-6361/201834344](https://doi.org/10.1051%2F0004-6361%2F201834344). [S2CID](/source/S2CID_(identifier)) [119073661](https://api.semanticscholar.org/CorpusID:119073661).

1. ^ [***a***](#cite_ref-Feng2022_13-0) [***b***](#cite_ref-Feng2022_13-1) Feng, Fabo; Butler, R. Paul; et al. (August 2022). ["3D Selection of 167 Substellar Companions to Nearby Stars"](https://doi.org/10.3847%2F1538-4365%2Fac7e57). *[The Astrophysical Journal Supplement Series](/source/The_Astrophysical_Journal_Supplement_Series)*. **262** (21): 21. [arXiv](/source/ArXiv_(identifier)):[2208.12720](https://arxiv.org/abs/2208.12720). [Bibcode](/source/Bibcode_(identifier)):[2022ApJS..262...21F](https://ui.adsabs.harvard.edu/abs/2022ApJS..262...21F). [doi](/source/Doi_(identifier)):[10.3847/1538-4365/ac7e57](https://doi.org/10.3847%2F1538-4365%2Fac7e57). [S2CID](/source/S2CID_(identifier)) [251864022](https://api.semanticscholar.org/CorpusID:251864022).

1. ^ [***a***](#cite_ref-Fontanet2025_14-0) [***b***](#cite_ref-Fontanet2025_14-1) Fontanet, E.; Udry, S.; et al. (May 2025). "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". *[Astronomy & Astrophysics](/source/Astronomy_%26_Astrophysics)*. [arXiv](/source/ArXiv_(identifier)):[2505.14317](https://arxiv.org/abs/2505.14317).

1. **[^](#cite_ref-Martinache_et_al_2018_15-0)** Martinache, Frantz; Ireland, Michael J. (2018). "Kernel-nulling for a robust direct interferometric detection of extrasolar planets". *Astronomy & Astrophysics*. **619**: A87. [arXiv](/source/ArXiv_(identifier)):[1802.06252](https://arxiv.org/abs/1802.06252). [Bibcode](/source/Bibcode_(identifier)):[2018A&A...619A..87M](https://ui.adsabs.harvard.edu/abs/2018A&A...619A..87M). [doi](/source/Doi_(identifier)):[10.1051/0004-6361/201832847](https://doi.org/10.1051%2F0004-6361%2F201832847). [S2CID](/source/S2CID_(identifier)) [118882482](https://api.semanticscholar.org/CorpusID:118882482).

v t e Constellation of Centaurus List of stars in Centaurus Centaurus in Chinese astronomy Stars Bayer α A (Rigil Kentaurus) B (Toliman) C (Proxima Centauri) β (Hadar) γ δ ε ζ (Leepwal) η θ (Menkent) ι (Kulou) κ λ μ ν (Heng) ξ1 ξ2 ο1 ο2 π ρ σ τ υ1 υ2 φ χ ψ x1 x2 C3 D E F G H J K M N Q Flamsteed 1 (i) 2 (g) 3 (k) 4 (h) Variable R T V Y RR SV SX BV DY UY V346 V553 V744 V752 V761 (a) V763 (C1) V766 V779 (Krzemiński's star) V803 V810 V816 (Przybylski's Star) V831 V842 V885 V886 V863 V1032 V1369 V1400 V1935 HR 4460 (A) 4466 (C2) 4499 4522 4523 4537 (j) 4546 (B) 4721 4748 (u) 4796 4817 (l) 4831 (w) 4874 (p) 4888 (e) 4889 (n) 4940 (f) 4979 4989 5006 (r) 5041 (m) 5089 (d) 5174 (z) 5222 (y) 5224 5241 5297 5358 (v) 5371 5471 (b) 5485 (c1) 5489 (c2) HD 97413 98176 100453 101581 101930 102117 (Uklun) 103197 107914 108236 109749 110113 113538 113766 114386 114729 115600 116434 (Matza) 117207 117618 (Dofida) 117939 120411 121228 121504 124448 (Popper's Star) 125072 125595 131399 Other 2MASS J1126−5003 2M1207 Gaia BH2 HD 131399 Ab PSR B1259−63 PSR J1311−3430 TOI-763 WASP-15 (Nyamien) WASP-41 WASP-42 WASP-167/KELT-13 Exoplanets 2M1207b b Centauri b HD 101930 b HD 102117 b (Leklsullun) HD 103197 b HD 109749 b HD 113538 b c HD 114386 b HD 114729 b HD 117207 b HD 117618 b (Noifasui) HD 121504 b HIP 65426 b (Najsakopajk) HIP 67522 b NGTS-13b Proxima Centauri b c d WASP-15b (Asye) Star clusters NGC 3766 4230 4507 5281 5286 5316 5460 5617 5662 Other IC 2944 ω Centauri Scorpius–Centaurus association Stock 16 Nebulae NGC 3918 5307 Other Boomerang Nebula Fleming 1 G292.0+1.8 G306.3-0.9 Gum 41 IC 2944 IRAS 13208−6020 RCW 79 RCW 86 Southern Crab Nebula SuWt 2 Galaxies NGC 3557 3568 3749 3783 4444 4603 4622 4650A 4683 4696 4706 4709 4729 4730 4743 4744 4909 4930 4945 4976 5011 A 5026 5064 5082 5090 5091 5102 5114 5121 5128 (Centaurus A) 5161 5206 5253 5266 5291 5398 5408 5419 5483 5516 Other ESO 269-57 ESO 325-4 ESO 383-76 ESO 444-46 Fourcade-Figueroa Object IC 3370 IC 4214 IC 4329A IRAS 13224−3809 J1144−4308 LEDA 677373 PKS 1144−379 PKS 1353−341 PKS 1424−418 Galaxy clusters Abell S740 Centaurus Cluster Shapley Supercluster Astronomical events GW190521 SN 185 SN 1895B (Z) SN 1972E SN 1986G J1407b SN 2019so Category

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