# Lambda Hydrae

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Star in the constellation Hydra

λ Hydrae Location of λ Hydrae (circled) Observation data Epoch J2000 Equinox J2000 Constellation Hydra Right ascension 10h 10m 35.27667s[1] Declination −12° 21′ 14.6938″[1] Apparent magnitude (V) 3.61[2] Characteristics Evolutionary stage red clump[3] Spectral type K0IIIbCN0.5[4] U−B color index +0.92[5] B−V color index +1.00[5] Astrometry Radial velocity (Rv) 19.4[6] km/s Proper motion (μ) RA: −201.27[1] mas/yr Dec.: −99.63[1] mas/yr Parallax (π) 30.0232±0.6973 mas[7] Distance 109 ± 3 ly (33.3 ± 0.8 pc) Absolute magnitude (MV) +0.92[8] Orbit[9] Period (P) 1585.8 days Semi-major axis (a) 16.79 mas Eccentricity (e) 0.138 Inclination (i) 79.49° Longitude of the node (Ω) 249.62° Periastron epoch (T) 2448664.3906 Argument of periastron (ω) (secondary) 238.9° Details λ Hya A Mass 1-2[10] M☉ Radius 8.62+0.22 −0.23[11] R☉ Luminosity 39.8[10] L☉ Surface gravity (log g) 2.64[10] cgs Temperature 4,656[10] K Metallicity [Fe/H] +0.25[12] dex Rotational velocity (v sin i) 1.9[13] km/s Other designations λ Hya, 41 Hydrae, BD−11°2820, HD 88284, HIP 49841, SAO 155785, HR 3994, GC 13982, TYC 5485-1310-1 Database references SIMBAD data

**λ Hydrae**, Latinised as **Lambda Hydrae**, is a [spectroscopic binary](/source/Spectroscopic_binary)[14] [star](/source/Star) in the [constellation](/source/Constellation) [Hydra](/source/Hydra_(constellation)). Its apparent magnitude is 3.61 Located around 33.3 parsecs (109 ly) distant. The [spiral galaxy](/source/Spiral_galaxy) [NGC 3145](https://en.wikipedia.org/w/index.php?title=NGC_3145&action=edit&redlink=1) is only 7.8[′](/source/Minute_of_arc) away to the southwest.

The primary is an [orange giant](/source/Orange_giant) of spectral type K0IIICN+1,[15] a star that has used up its core [hydrogen](/source/Hydrogen), left the [main sequence](/source/Main_sequence), and expanded into a [giant](/source/Giant_star). It is considered to be a [red clump](/source/Red_clump) giant, a cool [horizontal branch](/source/Horizontal_branch) star that is burning helium in its core.[3]

λ Hydrae has two visual companions, components B and C, 11th and 13th magnitude stars respectively 71[″](/source/Second_of_arc) and 111″ away.[16]

## References

1. ^ [***a***](#cite_ref-vanLeeuwen2007_1-0) [***b***](#cite_ref-vanLeeuwen2007_1-1) [***c***](#cite_ref-vanLeeuwen2007_1-2) [***d***](#cite_ref-vanLeeuwen2007_1-3) van Leeuwen, F. (November 2007). "Validation of the new Hipparcos reduction". *Astronomy and Astrophysics*. **474** (2): 653–664. [arXiv](/source/ArXiv_(identifier)):[0708.1752](https://arxiv.org/abs/0708.1752). [Bibcode](/source/Bibcode_(identifier)):[2007A&A...474..653V](https://ui.adsabs.harvard.edu/abs/2007A&A...474..653V). [doi](/source/Doi_(identifier)):[10.1051/0004-6361:20078357](https://doi.org/10.1051%2F0004-6361%3A20078357). [S2CID](/source/S2CID_(identifier)) [18759600](https://api.semanticscholar.org/CorpusID:18759600).

1. **[^](#cite_ref-Ducati2002_2-0)** Ducati, J. R. (2002). "VizieR Online Data Catalog: Catalogue of Stellar Photometry in Johnson's 11-color system". *CDS/ADC Collection of Electronic Catalogues*. **2237**: 0. [Bibcode](/source/Bibcode_(identifier)):[2002yCat.2237....0D](https://ui.adsabs.harvard.edu/abs/2002yCat.2237....0D).

1. ^ [***a***](#cite_ref-alves_3-0) [***b***](#cite_ref-alves_3-1) Alves, David R. (2000). ["K-Band Calibration of the Red Clump Luminosity"](https://doi.org/10.1086%2F309278). *The Astrophysical Journal*. **539** (2): 732–741. [arXiv](/source/ArXiv_(identifier)):[astro-ph/0003329](https://arxiv.org/abs/astro-ph/0003329). [Bibcode](/source/Bibcode_(identifier)):[2000ApJ...539..732A](https://ui.adsabs.harvard.edu/abs/2000ApJ...539..732A). [doi](/source/Doi_(identifier)):[10.1086/309278](https://doi.org/10.1086%2F309278).

1. **[^](#cite_ref-perkins_4-0)** Keenan, Philip C.; McNeil, Raymond C. (1989). "The Perkins Catalog of Revised MK Types for the Cooler Stars". *The Astrophysical Journal Supplement Series*. **71**: 245. [Bibcode](/source/Bibcode_(identifier)):[1989ApJS...71..245K](https://ui.adsabs.harvard.edu/abs/1989ApJS...71..245K). [doi](/source/Doi_(identifier)):[10.1086/191373](https://doi.org/10.1086%2F191373).

1. ^ [***a***](#cite_ref-UBV_5-0) [***b***](#cite_ref-UBV_5-1) Jennens, P. A. (1975). ["A new photometric metal abundance and luminosity calibration for field G and K giants"](https://doi.org/10.1093%2Fmnras%2F172.3.667). *Monthly Notices of the Royal Astronomical Society*. **172** (3): 667–679. [Bibcode](/source/Bibcode_(identifier)):[1975MNRAS.172..667J](https://ui.adsabs.harvard.edu/abs/1975MNRAS.172..667J). [doi](/source/Doi_(identifier)):[10.1093/mnras/172.3.667](https://doi.org/10.1093%2Fmnras%2F172.3.667).

1. **[^](#cite_ref-rv_6-0)** Wilson, Ralph Elmer (1953). "General catalogue of stellar radial velocities". *Carnegie Institute Washington D.C. Publication*: 0. [Bibcode](/source/Bibcode_(identifier)):[1953GCRV..C......0W](https://ui.adsabs.harvard.edu/abs/1953GCRV..C......0W).

1. **[^](#cite_ref-dr2_7-0)** [Brown, A. G. A.](/source/Anthony_Brown_(scientist)); et al. ([Gaia collaboration](/source/Data_Processing_and_Analysis_Consortium)) (August 2018). ["*Gaia* Data Release 2: Summary of the contents and survey properties"](https://doi.org/10.1051%2F0004-6361%2F201833051). *[Astronomy & Astrophysics](/source/Astronomy_%26_Astrophysics)*. **616**. A1. [arXiv](/source/ArXiv_(identifier)):[1804.09365](https://arxiv.org/abs/1804.09365). [Bibcode](/source/Bibcode_(identifier)):[2018A&A...616A...1G](https://ui.adsabs.harvard.edu/abs/2018A&A...616A...1G). [doi](/source/Doi_(identifier)):[10.1051/0004-6361/201833051](https://doi.org/10.1051%2F0004-6361%2F201833051). [Gaia DR2 record for this source](https://vizier.u-strasbg.fr/viz-bin/VizieR-S?Gaia%20DR2%203765867289804452608) at [VizieR](/source/VizieR).

1. **[^](#cite_ref-Anderson2012_8-0)** Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", *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), [S2CID](/source/S2CID_(identifier)) [119257644](https://api.semanticscholar.org/CorpusID:119257644).

1. **[^](#cite_ref-9)** ESA (1997). "The Hipparcos and Tycho Catalogues". *VizieR On-line Data Catalog*. [Bibcode](/source/Bibcode_(identifier)):[1997yCat.1239....0E](https://ui.adsabs.harvard.edu/abs/1997yCat.1239....0E).

1. ^ [***a***](#cite_ref-cruzabeles_10-0) [***b***](#cite_ref-cruzabeles_10-1) [***c***](#cite_ref-cruzabeles_10-2) [***d***](#cite_ref-cruzabeles_10-3) Cruzalèbes, P.; Rabbia, Y.; Jorissen, A.; Spang, A.; Sacuto, S.; Pasquato, E.; Chiavassa, A.; Chesneau, O.; Fréville, P. (2013). ["SPIDAST: A new modular software to process spectrointerferometric measurements"](https://doi.org/10.1093%2Fmnras%2Fstt593). *Monthly Notices of the Royal Astronomical Society*. **432** (2): 1658. [arXiv](/source/ArXiv_(identifier)):[1304.1666](https://arxiv.org/abs/1304.1666). [Bibcode](/source/Bibcode_(identifier)):[2013MNRAS.432.1658C](https://ui.adsabs.harvard.edu/abs/2013MNRAS.432.1658C). [doi](/source/Doi_(identifier)):[10.1093/mnras/stt593](https://doi.org/10.1093%2Fmnras%2Fstt593).

1. **[^](#cite_ref-Baines2025_11-0)** Baines, Ellyn K.; Clark, James H.; Kingsley, Bradley I.; Schmitt, Henrique R.; Stone, Jordan M. (2025-05-07). ["Vintage NPOI: New and Updated Angular Diameters for 145 Stars"](https://doi.org/10.3847%2F1538-3881%2Fadc930). *The Astronomical Journal*. **169** (6): 293. [arXiv](/source/ArXiv_(identifier)):[2506.02912](https://arxiv.org/abs/2506.02912). [Bibcode](/source/Bibcode_(identifier)):[2025AJ....169..293B](https://ui.adsabs.harvard.edu/abs/2025AJ....169..293B). [doi](/source/Doi_(identifier)):[10.3847/1538-3881/adc930](https://doi.org/10.3847%2F1538-3881%2Fadc930). [ISSN](/source/ISSN_(identifier)) [1538-3881](https://search.worldcat.org/issn/1538-3881).

1. **[^](#cite_ref-hypatia_12-0)** Hinkel, Natalie R.; Timmes, F. X.; Young, Patrick A.; Pagano, Michael D.; Turnbull, Margaret C. (2014). "Stellar Abundances in the Solar Neighborhood: The Hypatia Catalog". *The Astronomical Journal*. **148** (3): 54. [arXiv](/source/ArXiv_(identifier)):[1405.6719](https://arxiv.org/abs/1405.6719). [Bibcode](/source/Bibcode_(identifier)):[2014AJ....148...54H](https://ui.adsabs.harvard.edu/abs/2014AJ....148...54H). [doi](/source/Doi_(identifier)):[10.1088/0004-6256/148/3/54](https://doi.org/10.1088%2F0004-6256%2F148%2F3%2F54). [S2CID](/source/S2CID_(identifier)) [119221402](https://api.semanticscholar.org/CorpusID:119221402).

1. **[^](#cite_ref-13)** De Medeiros, J. R.; Da Silva, J. R. P.; Maia, M. R. G. (2002). ["The Rotation of Binary Systems with Evolved Components"](https://doi.org/10.1086%2F342613). *The Astrophysical Journal*. **578** (2): 943–950. [arXiv](/source/ArXiv_(identifier)):[astro-ph/0207288](https://arxiv.org/abs/astro-ph/0207288). [Bibcode](/source/Bibcode_(identifier)):[2002ApJ...578..943D](https://ui.adsabs.harvard.edu/abs/2002ApJ...578..943D). [doi](/source/Doi_(identifier)):[10.1086/342613](https://doi.org/10.1086%2F342613).

1. **[^](#cite_ref-Eggleton2008_14-0)** Eggleton, P. P.; Tokovinin, A. A. (September 2008). ["A catalogue of multiplicity among bright stellar systems"](https://doi.org/10.1111%2Fj.1365-2966.2008.13596.x). *[Monthly Notices of the Royal Astronomical Society](/source/Monthly_Notices_of_the_Royal_Astronomical_Society)*. **389** (2): 869–879. [arXiv](/source/ArXiv_(identifier)):[0806.2878](https://arxiv.org/abs/0806.2878). [Bibcode](/source/Bibcode_(identifier)):[2008MNRAS.389..869E](https://ui.adsabs.harvard.edu/abs/2008MNRAS.389..869E). [doi](/source/Doi_(identifier)):[10.1111/j.1365-2966.2008.13596.x](https://doi.org/10.1111%2Fj.1365-2966.2008.13596.x). [S2CID](/source/S2CID_(identifier)) [14878976](https://api.semanticscholar.org/CorpusID:14878976).

1. **[^](#cite_ref-Gray2006_15-0)** 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](/source/The_Astronomical_Journal)*. **132** (1): 161–170. [arXiv](/source/ArXiv_(identifier)):[astro-ph/0603770](https://arxiv.org/abs/astro-ph/0603770). [Bibcode](/source/Bibcode_(identifier)):[2006AJ....132..161G](https://ui.adsabs.harvard.edu/abs/2006AJ....132..161G). [doi](/source/Doi_(identifier)):[10.1086/504637](https://doi.org/10.1086%2F504637). [S2CID](/source/S2CID_(identifier)) [119476992](https://api.semanticscholar.org/CorpusID:119476992).

1. **[^](#cite_ref-wds_16-0)** Mason, Brian D.; Wycoff, Gary L.; Hartkopf, William I.; Douglass, Geoffrey G.; Worley, Charles E. (2001). ["The 2001 US Naval Observatory Double Star CD-ROM. I. The Washington Double Star Catalog"](https://doi.org/10.1086%2F323920). *The Astronomical Journal*. **122** (6): 3466. [Bibcode](/source/Bibcode_(identifier)):[2001AJ....122.3466M](https://ui.adsabs.harvard.edu/abs/2001AJ....122.3466M). [doi](/source/Doi_(identifier)):[10.1086/323920](https://doi.org/10.1086%2F323920).

v t e Constellation of Hydra List of stars in Hydra Hydra in Chinese astronomy Stars Bayer α (Alphard) β γ (Naga) δ ε (Ashlesha) ζ η θ ι (Ukdah) κ λ μ ν ξ ο π ρ σ (Minchir) τ1 τ2 υ1 (Zhang) υ2 φ1 φ2 φ3 χ1 χ2 ψ ω b1 b3 C F Flamsteed 1 2 3 6 (a) 9 10 12 (D) 14 15 17 19 20 21 23 24 25 26 27 (P) 28 29 33 (A) 34 37 44 47 48 50 51 (k) 52 (l) 54 (m) 55 56 57 58 (Solitaire) 59 60 10 Crt 17 Crt 20 Crt 2 Sex Variable R U V W TW EX HS KU LQ V361 V419 V421 V478 V484 HR 3378 3538 3749 (G) 3750 3858 (I) 3862 3919 3923 (Felis) 4162 4328 4339 (β Ant) 4445 5265 HD 72659 74156 82943 86226 86264 90156 (γ Ant) Other 2MASS 1114−2618 ESO 439-26 Gliese 328 Gliese 357 Gliese 433 Gliese 453 GJ 3634 HAT-P-30 HE 1256−2738 HE 1327−2326 LHS 2065 LHS 3003 LTT 3780 SDSS J090745.0+024507 WASP-25 WASP-36 WASP-84 WASP-166 (Filetdor) WISE 0855−0714 WISEA J1141−3326 Exoplanets Gliese 357 d HD 72659 b HD 74156 b c HD 82943 b c HD 86226 b HD 86264 b TW Hydrae b (unconfirmed) WASP-193b Star clusters Messier 48 Messier 68 NGC 5694 Price-Whelan 1 Nebulae Abell 33 Abell 35 NGC 3242 Southern Owl Nebula Galaxies Messier 83 NGC 2617 2642 2697 2708 2758 2835 2848 2865 2890 2935 2936 2937 2960 2962 2986 2992 3030 3052 3054 3081 3109 3124 3200 3285 3285B 3290 3305 3307 3308 3309 3311 3312 3313 3314 3315 3316 3336 3369 3383 3393 3402 3463 3464 3585 3621 3673 3717 3904 3923 3936 4980 4993 5042 5061 5078 5085 5101 5135 5260 5264 5495 5626 Other 3C 196.1 AM 1316−241 Arp 7 CTQ 327 ESO 510-G13 GAMA202627 GLEAM J0917−0012 Hydra A IC 535 MRC 1138−262 Peekaboo Galaxy PKS 1151−348 RX J0911.4+0551 SDSS J0841+0101 TN J0924−2201 Tololo 1247−232 ZwCl 1693 BCG Galaxy clusters Abell 754 Abell 3411 Abell 3412 Bullet Group Hickson 40 Astronomical events GW170817 Category

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Adapted from the Wikipedia article [Lambda Hydrae](https://en.wikipedia.org/wiki/Lambda_Hydrae) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Lambda_Hydrae?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.