# HD 117939

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Star in the constellation Centaurus

HD 117939 Observation data Epoch J2000 Equinox J2000 Constellation Centaurus[1] Right ascension 13h 34m 32.64979s[2] Declination −38° 54′ 25.9678″[2] Apparent magnitude (V) 7.29[1] Characteristics Evolutionary stage Main sequence[2] Spectral type G4V[3] B−V color index 0.669±0.006[1] Astrometry Radial velocity (Rv) +82.23±0.12[2] km/s Proper motion (μ) RA: +445.183[2] mas/yr Dec.: −393.880[2] mas/yr Parallax (π) 33.1088±0.0267 mas[2] Distance 98.51 ± 0.08 ly (30.20 ± 0.02 pc) Absolute magnitude (MV) 4.90[1] Details Mass 0.92[4] M☉ Radius 1.01±0.04[4] R☉ Luminosity 1.00[5] L☉ Surface gravity (log g) 4.43[5] cgs Temperature 5,690[5] K Metallicity [Fe/H] −0.22±0.07[4] dex Rotation 2.18 days[6] Rotational velocity (v sin i) 1.0±1.0[4] km/s Age 6.1[7] Gyr Other designations CD−38°8635, GJ 9450, HD 117939, HIP 66238, SAO 204606, LHS 2760[8] Database references SIMBAD data

**HD 117939** is a Sun-like star in the southern [constellation](/source/Constellation) of [Centaurus](/source/Centaurus). With an [apparent visual magnitude](/source/Apparent_visual_magnitude) of 7.29[1] it is too faint to be viewed with the naked eye, but is within the range of binoculars or a small telescope. It is located at a distance of 98.5 [light years](/source/Light_year) from the [Sun](/source/Sun) based on [parallax](/source/Stellar_parallax) measurements, and is drifting further away with a [radial velocity](/source/Radial_velocity) of +82 km/s. This is an intermediate disk[4] star with a high [proper motion](/source/Proper_motion), traversing the [celestial sphere](/source/Celestial_sphere) at an [angular rate](/source/Angular_rate) of 0.68 arcsec yr−1.[9]

An ordinary [G-type main-sequence star](/source/G-type_main-sequence_star) with a [stellar classification](/source/Stellar_classification) of G4V,[3] this star is an "excellent [photometric](/source/Photometry_(astronomy)) match for the Sun";[7] the atmospheric properties of the star make it a near [solar twin](/source/Solar_twin). It is older than the sun at 6.1 billion years, but is more [chromospherically active](/source/Magnetic_activity).[7]

To date no exact solar twin (precisely matching all important properties of the Sun) has been found. However, there are some stars that come very close to being identical to the Sun, and as such are dubbed [solar twins](/source/Solar_twin) by astronomers. An exact solar twin would be a 4.6 billion years old G2V star with a 5,772K temperature, the correct metallicity, and a 0.1% [solar luminosity](/source/Solar_luminosity) variation.[10] G2V stars with an age of 4.6 billion years or more have typically reached their most stable state. Proper metallicity and size are also important to low luminosity variation.[11][12]

## Sun comparison

Chart compares the sun to HD 117939.

Identifier Stellar Class Temperature (K) Metallicity (dex) Age (Gyr) Notes Sun G2V 5,778 +0.00 4.6 [13] HD 117939 G4V 5,765 −0.22 6.1 [7][4]

## See also

- [List of nearest stars](/source/List_of_nearest_stars)

## References

1. ^ [***a***](#cite_ref-Anderson_Francis_2012_1-0) [***b***](#cite_ref-Anderson_Francis_2012_1-1) [***c***](#cite_ref-Anderson_Francis_2012_1-2) [***d***](#cite_ref-Anderson_Francis_2012_1-3) [***e***](#cite_ref-Anderson_Francis_2012_1-4) 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=66238&-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%3D6161806515182527616%26-go+%25%23Sesame%23%25%26) at [VizieR](/source/VizieR).

1. ^ [***a***](#cite_ref-Gray_et_al_2006_3-0) [***b***](#cite_ref-Gray_et_al_2006_3-1) 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. ^ [***a***](#cite_ref-Fuhrmann_Chini_2019_4-0) [***b***](#cite_ref-Fuhrmann_Chini_2019_4-1) [***c***](#cite_ref-Fuhrmann_Chini_2019_4-2) [***d***](#cite_ref-Fuhrmann_Chini_2019_4-3) [***e***](#cite_ref-Fuhrmann_Chini_2019_4-4) [***f***](#cite_ref-Fuhrmann_Chini_2019_4-5) Fuhrmann, Klaus; Chini, Rolf (January 2019). ["On ancient solar-type stars"](https://doi.org/10.1093%2Fmnras%2Fsty2660). *Monthly Notices of the Royal Astronomical Society*. **482** (1): 471–489. [Bibcode](/source/Bibcode_(identifier)):[2019MNRAS.482..471F](https://ui.adsabs.harvard.edu/abs/2019MNRAS.482..471F). [doi](/source/Doi_(identifier)):[10.1093/mnras/sty2660](https://doi.org/10.1093%2Fmnras%2Fsty2660).

1. ^ [***a***](#cite_ref-tic_5-0) [***b***](#cite_ref-tic_5-1) [***c***](#cite_ref-tic_5-2) Stassun, Keivan G.; et al. (2019). ["The Revised TESS Input Catalog and Candidate Target List"](https://doi.org/10.3847%2F1538-3881%2Fab3467). *The Astronomical Journal*. **158** (4): 138. [arXiv](/source/ArXiv_(identifier)):[1905.10694](https://arxiv.org/abs/1905.10694). [Bibcode](/source/Bibcode_(identifier)):[2019AJ....158..138S](https://ui.adsabs.harvard.edu/abs/2019AJ....158..138S). [doi](/source/Doi_(identifier)):[10.3847/1538-3881/ab3467](https://doi.org/10.3847%2F1538-3881%2Fab3467).

1. **[^](#cite_ref-oelkers2018_6-0)** Oelkers, Ryan J.; Rodriguez, Joseph E.; Stassun, Keivan G.; Pepper, Joshua; Somers, Garrett; Kafka, Stella; Stevens, Daniel J.; Beatty, Thomas G.; Siverd, Robert J.; Lund, Michael B.; Kuhn, Rudolf B.; James, David; Gaudi, B. Scott (2018). ["Variability Properties of Four Million Sources in the TESS Input Catalog Observed with the Kilodegree Extremely Little Telescope Survey"](https://doi.org/10.3847%2F1538-3881%2Faa9bf4). *The Astronomical Journal*. **155** (1): 39. [arXiv](/source/ArXiv_(identifier)):[1711.03608](https://arxiv.org/abs/1711.03608). [Bibcode](/source/Bibcode_(identifier)):[2018AJ....155...39O](https://ui.adsabs.harvard.edu/abs/2018AJ....155...39O). [doi](/source/Doi_(identifier)):[10.3847/1538-3881/aa9bf4](https://doi.org/10.3847%2F1538-3881%2Faa9bf4).

1. ^ [***a***](#cite_ref-Porto_de_Mello_et_al_2014_7-0) [***b***](#cite_ref-Porto_de_Mello_et_al_2014_7-1) [***c***](#cite_ref-Porto_de_Mello_et_al_2014_7-2) [***d***](#cite_ref-Porto_de_Mello_et_al_2014_7-3) Porto de Mello, G. F.; et al. (March 2014). "A photometric and spectroscopic survey of solar twin stars within 50 parsecs of the Sun. I. Atmospheric parameters and color similarity to the Sun". *Astronomy & Astrophysics*. **563**: 25. [arXiv](/source/ArXiv_(identifier)):[1312.7571](https://arxiv.org/abs/1312.7571). [Bibcode](/source/Bibcode_(identifier)):[2014A&A...563A..52P](https://ui.adsabs.harvard.edu/abs/2014A&A...563A..52P). [doi](/source/Doi_(identifier)):[10.1051/0004-6361/201322277](https://doi.org/10.1051%2F0004-6361%2F201322277). [S2CID](/source/S2CID_(identifier)) [119111150](https://api.semanticscholar.org/CorpusID:119111150). A52.

1. **[^](#cite_ref-SIMBAD_8-0)** ["HD 117939"](http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=HD+117939). *[SIMBAD](/source/SIMBAD)*. [Centre de données astronomiques de Strasbourg](/source/Centre_de_donn%C3%A9es_astronomiques_de_Strasbourg). Retrieved 2016-09-26.

1. **[^](#cite_ref-Bakos_et_al_2002_9-0)** Bakos, Gáspár Á.; et al. (July 2002). "Revised Coordinates and Proper Motions of the Stars in the Luyten Half-Second Catalog". *The Astrophysical Journal Supplement Series*. **141** (1): 187–193. [arXiv](/source/ArXiv_(identifier)):[astro-ph/0202164](https://arxiv.org/abs/astro-ph/0202164). [Bibcode](/source/Bibcode_(identifier)):[2002ApJS..141..187B](https://ui.adsabs.harvard.edu/abs/2002ApJS..141..187B). [doi](/source/Doi_(identifier)):[10.1086/340115](https://doi.org/10.1086%2F340115). [S2CID](/source/S2CID_(identifier)) [36667868](https://api.semanticscholar.org/CorpusID:36667868).

1. **[^](#cite_ref-NASA_2013_10-0)** ["Solar Variability and Terrestrial Climate"](https://science.nasa.gov/science-news/science-at-nasa/2013/08jan_sunclimate/). *Science News*. NASA. January 8, 2013.

1. **[^](#cite_ref-UNL_11-0)** ["Stellar Luminosity Calculator"](http://astro.unl.edu/classaction/animations/stellarprops/stellarlum.html). University of Nebraska-Lincoln astronomy education group.

1. **[^](#cite_ref-NAP_12-0)** ["The Effects of Solar Variability on Earth's Climate, 2012 Report"](http://www.nap.edu/catalog/13519/the-effects-of-solar-variability-on-earths-climate-a-workshop). National Center for Atmospheric Research.

1. **[^](#cite_ref-nssdc_13-0)** Williams, D. R. (2004). ["Sun Fact Sheet"](https://nssdc.gsfc.nasa.gov/planetary/factsheet/sunfact.html). [NASA](/source/NASA). Retrieved 2009-06-23.

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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Adapted from the Wikipedia article [HD 117939](https://en.wikipedia.org/wiki/HD_117939) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/HD_117939?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.