# 18 Sextantis

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K-type giant star in the constellation Sextans

18 Sextantis Location of 18 Sex on the map (circled) Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) Constellation Sextans Right ascension 10h 10m 55.86074s[1] Declination −08° 25′ 06.4527″[1] Apparent magnitude (V) 5.62±0.01[2] Characteristics Spectral type K2/3 III[3] U−B color index +1.42[4] B−V color index +1.30[4] Astrometry Radial velocity (Rv) 0.2±2.9[5] km/s Proper motion (μ) RA: −0.115 mas/yr[1] Dec.: −43.987 mas/yr[1] Parallax (π) 5.8416±0.0881 mas[1] Distance 558 ± 8 ly (171 ± 3 pc) Absolute magnitude (MV) −0.16[6] Details Radius 27.3±1.4[7] R☉ Luminosity 222±12[8] L☉ Surface gravity (log g) 1.72[9] cgs Temperature 4,410±122[10] K Metallicity [Fe/H] −0.31+0.01 −0.00[11] dex Rotational velocity (v sin i) <1.0[12] km/s Other designations 18 Sex, 32 G. Sextantis[13], BD−07°2977, GC 13990, HD 88333, HIP 49865, HR 3996, SAO 137395, TIC 26206896[14] Database references SIMBAD data

**18 Sextantis** (**HD 88333; HR 3996; 32 G. Sextantis**), or simply **18 Sex**, is a solitary [star](/source/Star)[15] located in the southern [constellation](/source/Constellation) [Sextans](/source/Sextans). It is faintly visible to the [naked eye](/source/Naked_eye) as an orange-hued point of light with an [apparent magnitude](/source/Apparent_magnitude) of 5.62.[2] [Gaia DR3](/source/Gaia_DR3) [parallax](/source/Parallax) measurements imply a distance of 558 [light-years](/source/Light-year)[1] and it is slowly receding with a poorly constrained heliocentric [radial velocity](/source/Radial_velocity) of approximately 0.2 [km/s](/source/Metre_per_second).[5] At its current distance, 18 Sex's brightness is diminished with an [interstellar extinction](/source/Interstellar_extinction) of two-tenths of a [magnitude](/source/Magnitude_(astronomy))[16] and it has an [absolute magnitude](/source/Absolute_magnitude) of −0.16.[6]

18 Sex has a [stellar classification](/source/Stellar_classification) of K2/3 III,[3] indicating that it is an [evolved](/source/Stellar_evolution) star with the characteristics of a K2 and K3 [giant star](/source/Giant_star). At present, it has exhausted [hydrogen](/source/Hydrogen) at its [core](/source/Stellar_core) and it has expanded to 27.3 times the [radius of the Sun](/source/Radius_of_the_Sun).[7] It radiates 222 times the [luminosity of the Sun](/source/Luminosity_of_the_Sun)[8] from its enlarged [photosphere](/source/Photosphere) at an [effective temperature](/source/Effective_temperature) of 4,410 [K](/source/Kelvin).[10] Gaia DR3 models it to be a larger and brighter [red giant branch](/source/Red_giant_branch) star with a radius of 35.27 [*R*☉](/source/Solar_radius) and a [luminosity](/source/Luminosity) of 384 [L☉](/source/Solar_luminosity).[1] 18 Sex is metal deficient with an [iron](/source/Iron) abundance of [Fe/H] = −0.31 or 49% of the [Sun](/source/Sun)'s[11] and it spins too slowly for its [projected rotational velocity](/source/Projected_rotational_velocity) to be measured accurately, having a velocity lower than 1.0 [km/s](/source/Metre_per_second).[12]

## See also

- [17 Sextantis](https://en.wikipedia.org/w/index.php?title=17_Sextantis&action=edit&redlink=1), an [A-type main-sequence star](/source/A-type_main-sequence_star) located 12' away.

## References

1. ^ [***a***](#cite_ref-GaiaDR3_1-0) [***b***](#cite_ref-GaiaDR3_1-1) [***c***](#cite_ref-GaiaDR3_1-2) [***d***](#cite_ref-GaiaDR3_1-3) [***e***](#cite_ref-GaiaDR3_1-4) [***f***](#cite_ref-GaiaDR3_1-5) 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%3D3771960229193854080%26-go+%25%23Sesame%23%25%26) at [VizieR](/source/VizieR).

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1. **[^](#cite_ref-SIMBAD_14-0)** ["* 18 Sex"](http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=%2A+18+Sex). *[SIMBAD](/source/SIMBAD)*. [Centre de données astronomiques de Strasbourg](/source/Centre_de_donn%C3%A9es_astronomiques_de_Strasbourg).

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v t e Constellation of Sextans COSMOS field List of stars in Sextans Sextans in Chinese astronomy Stars Bayer α β γ δ ε Flamsteed 7 18 19 23 24 25 35 41 Variable Y UY HR 3879 3915 4092 4233 HD 86081 (Bibhā) 92788 93396 Other BD−08°2823 Gliese 393 K2-239 LHS 292 PSR J0952−0607 TOI-561 WASP-43 (Gnomon) WASP-127 Exoplanets BD−08°2823 b c HD 86081 b (Santamasa) HD 92788 b KELT-11b TOI-561 b WASP-43b (Astrolábos) Galaxies NGC 2967 2974 2980 3007 3015 3018 3044 3110 3115 3156 3166 3169 3326 3341 3423 Other 3MM-1 AzTECC71 Baby Boom Galaxy CAPERS-LRD-z9 CID-42 CID-346 Cosmos Redshift 7 HD1 Infinity Galaxy J1000+0221 J1010+0612 J10405643–0103584 LAE J095950.99+021219.1 LBQS 1009−0252 MoM-z14 PG 1011−040 PG 1012+008 PGC 29820 PGC 3092152 PMN J0948+0022 REBELS-25 Sextans A Sextans B Sextans Dwarf Spheroidal Zhúlóng Galaxy clusters Abell 907 CL J1001+0220 Hyperion proto-supercluster Astronomical events AT 2018hyz SN 1000+0216 Category

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Adapted from the Wikipedia article [18 Sextantis](https://en.wikipedia.org/wiki/18_Sextantis) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/18_Sextantis?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.