18 Sextantis

{{Short description|K-type giant star in the constellation Sextans}} {{Starbox begin | name = [[Flamsteed designation|18 Sextantis]] }} {{Starbox image | image = {{Location mark | image = Sextans constellation map.svg | float = center | width = 260 | position = right | mark = Red circle.svg | mark_width = 6 | mark_link = 18 Sextantis | x = 508 | y = 850 }} | caption = Location of 18 Sex on the map (circled) }} {{Starbox observe | epoch = [[J2000.0]] ([[International Celestial Reference System|ICRS]]) | constell = [[Sextans]] | ra = {{RA|10|10|55.86074}}<ref name = GaiaDR3/> | dec = {{DEC|−08|25|06.4527}}<ref name = GaiaDR3/> | appmag_v = 5.62{{±|0.01}}<ref name = Tycho2000/> }} {{Starbox character | class = K2/3 III<ref name = Houk1999/> | b-v = +1.30<ref name = Johnson1966/> | u-b = +1.42<ref name = Johnson1966/> }} {{Starbox astrometry | radial_v = 0.2{{±|2.9}}<ref name = Gontcharov2006/> | parallax = 5.8416 | p_error = 0.0881 | parallax_footnote = <ref name = GaiaDR3/> | prop_mo_ra = −0.115 | prop_mo_dec = −43.987 | pm_footnote = <ref name = GaiaDR3/> | absmag_v = −0.16<ref name = Anderson2012/> }} {{Starbox detail | mass = | radius = 27.3{{±|1.4}}<ref name = Kervella2004/> | luminosity = 222{{±|12}}<ref name = GaiaDR2/> | gravity = 1.72<ref name = McDonald2017/> | temperature = 4,410{{±|122}}<ref name = Stassun2019/> | metal_fe = −0.31{{±|0.01|0.00}}<ref name = Poggio2022/> | rotational_velocity = <1.0<ref name = "De Medeiros2014"/> | age_gyr = }} {{Starbox catalog | names = {{odlist|F = 18 Sex|Gould = 32 G. Sextantis<ref name = Gould1879/>|BD = −07°2977|GC = 13990|HD = 88333|HIP = 49865|HR = 3996|SAO = 137395|TIC = 26206896}}<ref name = SIMBAD/> }} {{Starbox reference | Simbad = *18+Sex }} {{Starbox end}}

'''18 Sextantis''' ('''HD 88333; HR 3996; 32 G. Sextantis'''), or simply '''18 Sex''', is a solitary [[star]]<ref name = Eggleton2008/> located in the southern [[constellation]] [[Sextans]]. It is faintly visible to the [[naked eye]] as an orange-hued point of light with an [[apparent magnitude]] of 5.62.<ref name = Tycho2000/> [[Gaia DR3]] [[parallax]] measurements imply a distance of 558 [[light-year]]s<ref name = GaiaDR3/> and it is slowly receding with a poorly constrained heliocentric [[radial velocity]] of approximately {{val|0.2|ul=km/s}}.<ref name = Gontcharov2006/> At its current distance, 18 Sex's brightness is diminished with an [[interstellar extinction]] of two-tenths of a [[magnitude (astronomy)|magnitude]]<ref name = Gontcharov2017/> and it has an [[absolute magnitude]] of −0.16.<ref name = Anderson2012/>

18 Sex has a [[stellar classification]] of K2/3 III,<ref name = Houk1999/> indicating that it is an [[stellar evolution|evolved]] star with the characteristics of a K2 and K3 [[giant star]]. At present, it has exhausted [[hydrogen]] at its [[stellar core|core]] and it has expanded to 27.3 times the [[radius of the Sun]].<ref name = Kervella2004/> It radiates 222 times the [[luminosity of the Sun]]<ref name = GaiaDR2/> from its enlarged [[photosphere]] at an [[effective temperature]] of {{val|4410|ul=K|fmt=commas}}.<ref name = Stassun2019/> Gaia DR3 models it to be a larger and brighter [[red giant branch]] star with a radius of {{solar radius|35.27|link=y}} and a [[luminosity]] of {{solar luminosity|384|link=y}}.<ref name = GaiaDR3/> 18 Sex is metal deficient with an [[iron]] abundance of [Fe/H] = −0.31 or 49% of the [[Sun]]'s<ref name = Poggio2022/> and it spins too slowly for its [[projected rotational velocity]] to be measured accurately, having a velocity lower than {{val|1.0|ul=km/s}}.<ref name = "De Medeiros2014"/>

==See also== *[[17 Sextantis]], an [[A-type main-sequence star]] located 12' away.

==References== {{reflist||refs=

<ref name = Tycho2000>{{cite journal | last1 = Høg | first1 = E. | last2 = Fabricius | first2 = C. | last3 = Makarov | first3 = V. V. | last4 = Urban | first4 = S. | last5 = Corbin | first5 = T. | last6 = Wycoff | first6 = G. | last7 = Bastian | first7 = U. | last8 = Schwekendiek | first8 = P. | last9 = Wicenec | first9 = A. | title = The Tycho-2 catalogue of the 2.5 million brightest stars | journal = Astronomy and Astrophysics | date = March 2000 | volume = 355 | pages = L27–L30 | s2cid = 17128864 | bibcode = 2000A&A...355L..27H | issn = 0004-6361}}</ref>

<ref name = Houk1999>{{cite book | last1 = Houk | first1 = Nancy | last2 = Swift | first2 = Carrie | title = Michigan catalogue of two-dimensional spectral types for the HD Stars; vol. 5 | year = 1999 | bibcode = 1999mctd.book.....H}}</ref>

<ref name = Johnson1966>{{cite journal | last1 = Johnson | first1 = H. L. | last2 = Mitchell | first2 = R. I. | last3 = Iriarte | first3 = B. | last4 = Wisniewski | first4 = W. Z. | title = UBVRIJKL Photometry of the Bright Stars | journal = Communications of the Lunar and Planetary Laboratory | year = 1966 | volume = 4 | pages = 99–110 | bibcode = 1966CoLPL...4...99J}}</ref>

<ref name = Gontcharov2006>{{cite journal | last1 = Gontcharov | first1 = G. A. | title = Pulkovo Compilation of Radial Velocities for 35,495 Hipparcos stars in a common system | journal = Astronomy Letters | date = November 2006 | volume = 32 | issue = 11 | pages = 759–771 | issn = 1063-7737 | eissn = 1562-6873 | doi = 10.1134/S1063773706110065 | pmid = | bibcode = 2006AstL...32..759G | arxiv = 1606.08053 | s2cid = 119231169 }}</ref>

<ref name = "De Medeiros2014">{{cite journal | last1 = De Medeiros | first1 = J. R. | last2 = Alves | first2 = S. | last3 = Udry | first3 = S. | last4 = Andersen | first4 = J. | last5 = Nordström | first5 = B. | last6 = Mayor | first6 = M. | title = A catalog of rotational and radial velocities for evolved stars V: Southern stars * | journal = Astronomy & Astrophysics | date = January 2014 | volume = 561 | page = A126 | issn = 0004-6361 | eissn = 1432-0746 | doi = 10.1051/0004-6361/201220762 | bibcode = 2014A&A...561A.126D | arxiv = 1312.3474 | doi-access = free | s2cid = 54046583}}</ref>

<ref name = Kervella2004>{{cite journal | last1 = Kervella | first1 = P. | last2 = Thévenin | first2 = F. | last3 = Di Folco | first3 = E. | last4 = Ségransan | first4 = D. | title = The angular sizes of dwarf stars and subgiants: Surface brightness relations calibrated by interferometry | journal = Astronomy & Astrophysics | date = April 8, 2004 | volume = 426 | issue = 1 | pages = 297–307 | issn = 0004-6361 | eissn = 1432-0746 | doi = 10.1051/0004-6361:20035930 | s2cid = 6077801 | bibcode = 2004A&A...426..297K | arxiv = astro-ph/0404180 | doi-access = free}}</ref>

<ref name = Stassun2019>{{cite journal | display-authors = 1 | last1 = Stassun | first1 = Keivan G. | last2 = Oelkers | first2 = Ryan J. | last3 = Paegert | first3 = Martin | last4 = Torres | first4 = Guillermo | last5 = Pepper | first5 = Joshua | last6 = Lee | first6 = Nathan De | last7 = Collins | first7 = Kevin | last8 = Latham | first8 = David W. | last9 = Muirhead | first9 = Philip S. | last10 = Chittidi | first10 = Jay | last11 = Rojas-Ayala | first11 = Bárbara | last12 = Fleming | first12 = Scott W. | last13 = Rose | first13 = Mark E. | last14 = Tenenbaum | first14 = Peter | last15 = Ting | first15 = Eric B. | last16 = Kane | first16 = Stephen R. | last17 = Barclay | first17 = Thomas | last18 = Bean | first18 = Jacob L. | last19 = Brassuer | first19 = C. E. | last20 = Charbonneau | first20 = David | last21 = Ge | first21 = Jian | last22 = Lissauer | first22 = Jack J. | last23 = Mann | first23 = Andrew W. | last24 = McLean | first24 = Brian | last25 = Mullally | first25 = Susan | last26 = Narita | first26 = Norio | last27 = Plavchan | first27 = Peter | last28 = Ricker | first28 = George R. | last29 = Sasselov | first29 = Dimitar | last30 = Seager | first30 = S. | last31 = Sharma | first31 = Sanjib | last32 = Shiao | first32 = Bernie | last33 = Sozzetti | first33 = Alessandro | last34 = Stello | first34 = Dennis | last35 = Vanderspek | first35 = Roland | last36 = Wallace | first36 = Geoff | last37 = Winn | first37 = Joshua N. | title = The Revised ''TESS'' Input Catalog and Candidate Target List | journal = The Astronomical Journal | date = 9 September 2019 | volume = 158 | issue = 4 | page = 138 | eissn = 1538-3881 | doi = 10.3847/1538-3881/ab3467 | bibcode = 2019AJ....158..138S | arxiv = 1905.10694 | s2cid = 166227927 | hdl = 1721.1/124721 | hdl-access = free | doi-access = free}}</ref>

<ref name = Poggio2022>{{cite journal | last1 = Poggio | first1 = E. | last2 = Recio-Blanco | first2 = A. | last3 = Palicio | first3 = P. A. | last4 = Re Fiorentin | first4 = P. | last5 = de Laverny | first5 = P. | last6 = Drimmel | first6 = R. | last7 = Kordopatis | first7 = G. | last8 = Lattanzi | first8 = M. G. | last9 = Schultheis | first9 = M. | last10 = Spagna | first10 = A. | last11 = Spitoni | first11 = E. | title = The chemical signature of the Galactic spiral arms revealed by ''Gaia'' DR3 | journal = Astronomy & Astrophysics | date = 30 September 2022 | volume = 666 | page = L4 | issn = 0004-6361 | eissn = 1432-0746 | doi = 10.1051/0004-6361/202244361 | bibcode = 2022A&A...666L...4P | arxiv = 2206.14849 | doi-access = free}}</ref>

<ref name = Anderson2012>{{cite journal | last1 = Anderson | first1 = E. | last2 = Francis | first2 = Ch. | title = XHIP: An extended hipparcos compilation | journal = Astronomy Letters | date = May 2012 | volume = 38 | issue = 5 | pages = 331–346 | issn = 1063-7737 | eissn = 1562-6873 | doi = 10.1134/S1063773712050015 | bibcode = 2012AstL...38..331A | arxiv = 1108.4971| s2cid = 119257644}}</ref>

<ref name = Gould1879>{{cite journal | last = Gould | first = Benjamin Apthorp | title = Uranometria Argentina : brillantez y posicion de las estrellas fijas, hasta la septima magnitud, comprendidas dentro de cien grados del polo austral : con atlas | journal = Resultados del Observatorio Nacional Argentino | volume = 1 | bibcode = 1879RNAO....1.....G | year = 1878}}</ref>

<ref name = SIMBAD>{{Cite simbad|title = * 18 Sex|date= December 28, 2023}}</ref>

<ref name = McDonald2017>{{cite journal | last1 = McDonald | first1 = I. | last2 = Zijlstra | first2 = A. A. | last3 = Watson | first3 = R. A. | title = Fundamental parameters and infrared excesses of Tycho–Gaia stars | journal = Monthly Notices of the Royal Astronomical Society | date = 15 June 2017 | volume = 471 | issue = 1 | pages = 770–791 | issn = 0035-8711 | eissn = 1365-2966 | doi = 10.1093/mnras/stx1433 | bibcode = 2017MNRAS.471..770M | arxiv = 1706.02208 | s2cid = 73594365 | doi-access = free }}</ref>

<ref name = Gontcharov2017>{{cite journal | last1 = Gontcharov | first1 = George A. | last2 = Mosenkov | first2 = Aleksandr V. | title = Verifying reddening and extinction for Gaia DR1 TGAS main sequence stars | journal = Monthly Notices of the Royal Astronomical Society | date = 28 September 2017 | volume = 472 | issue = 4 | pages = 3805–3820 | issn = 0035-8711 | eissn = 1365-2966 | doi = 10.1093/mnras/stx2219 | bibcode = 2017MNRAS.472.3805G | arxiv = 1709.01160 | s2cid = 118879856 | doi-access = free}}</ref>

<ref name = Eggleton2008>{{cite journal | last1 = Eggleton | first1 = P. P. | last2 = Tokovinin | first2 = A. A. | title = A catalogue of multiplicity among bright stellar systems | journal = Monthly Notices of the Royal Astronomical Society | date = 11 September 2008 | volume = 389 | issue = 2 | pages = 869–879 | issn = 0035-8711 | eissn = 1365-2966 | doi = 10.1111/j.1365-2966.2008.13596.x | bibcode = 2008MNRAS.389..869E | arxiv = 0806.2878 | s2cid = 14878976 | doi-access = free }}</ref>

}} {{Stars of Sextans}}

[[Category:K-type giants]] [[Category:Sextans]] [[Category:Flamsteed objects|Sextantis, 18]] [[Category:Gould objects|Sextantis, 32]] [[Category:Durchmusterung objects|BD-07 02977]] [[Category:Henry Draper Catalogue objects|088333]] [[Category:Hipparcos objects|049865]] [[Category:Bright Star Catalogue objects|3996]]