{{Short description|Star in the constellation Taurus}} {{about|the star system|the Marvel Comics alien species|Chitauri|fraternities|Chi Tau|and|Chi Tau (local)}} {{Starbox begin}} {{Starbox image | image = {{Location mark | image=Taurus IAU.svg | float=center | width=250 | position=right | mark=Red circle.svg | mark_width=10 | mark_link=χ Tau | x%=59.2 | y%=27.8 }} | caption=Location of χ Tauri (circled) }} {{Starbox observe 2s |epoch=J2000 |constell=Taurus |component1=χ Tau A |ra1={{RA|04|22|34.944}}<ref name=dr2a/> |dec1={{DEC|+25|37|45.53}}<ref name=dr2a/> |appmag_v1=5.378<ref name=TYC2>{{cite journal|title=The Tycho-2 catalogue of the 2.5 million brightest stars|author=Høg, E.|display-authors=etal|date=2000|journal=Astronomy and Astrophysics|volume=355|pages=L27–L30|bibcode=2000A&A...355L..27H}}</ref> |component2=χ Tau B |ra2={{RA|04|22|35.550}}<ref name=dr2b/> |dec2={{DEC|+25|38|03.22}}<ref name=dr2b/> |appmag_v2=8.423<ref name=Torres/> }} {{Starbox character |component1=χ Tau A |class=B9V<ref name=Torres>{{cite journal|bibcode=2006AJ....131.1702T|arxiv=astro-ph/0512254|doi=10.1086/500355|title=The Multiple System HD 27638|journal=The Astronomical Journal|volume=131|issue=3|pages=1702–1711|year=2006|last1=Torres|first1=Guillermo|s2cid=119106287}}</ref> |b-v=-0.04<ref name=EgUBV>{{cite journal|author1=Mermilliod, J.-C.|title=Compilation of Eggen's UBV data, transformed to UBV (unpublished)|journal=Catalogue of Eggen's UBV Data|url=http://cdsads.u-strasbg.fr/cgi-bin/nph-bib_query?1986EgUBV........0M&db_key=AST&nosetcookie=1|date=1986|bibcode= 1986EgUBV........0M}}</ref> |u-b=-0.12<ref name=EgUBV/> |variable= |component2=χ Tau B |class2=F8 + G6 + K4 + K4<ref name=Torres/> |b-v2=+0.63<ref name=EgUBV/> |u-b2=+0.10<ref name=EgUBV/> |variable2= }} {{Starbox astrometry |component1=χ Tau A |radial_v={{val|+15.3|3.4}}<ref name=Torres/> |prop_mo_ra=+20.953<ref name=dr2a/> |prop_mo_dec=−16.495<ref name=dr2a/> |parallax=11.0472 |p_error=0.1599 |parallax_footnote=<ref name=dr2a>{{cite DR2|150461092453366528}}</ref> |absmag_v={{val|+0.82|0.18}}<ref name=Torres/> |component2=χ Tau B |radial_v2={{val|+14.694|0.081}}<ref name=Torres/> |prop_mo_ra2=15.766<ref name=dr2b/> |prop_mo_dec2=−20.396<ref name=dr2b/> |parallax2=11.5348 |p_error2=0.0857 |parallax_footnote2=<ref name=dr2b>{{cite DR2|150461092453290240}}</ref> |absmag_v2={{nowrap|'''Combined''': {{val|+3.85|0.18}}}}<br/>{{nowrap|'''Ba''': {{val|4.20|0.18}}}}<br/>{{nowrap|'''Bb''': {{val|5.27|0.18}}}}<br/>{{nowrap|'''Bc''': 7.87 / 7.87}}<ref name=Torres/> }} {{Starbox orbit |reference=<ref name=Torres/> |primary=χ Tau Ba |name=χ Tau Bb |period_unitless=17.602309 ± 0.000036 d |k1={{val|41.287|0.080}} |k2={{val|48.133|0.080}} |eccentricity={{val|0.2938|0.0013}} |periarg={{val|249.43|0.33}} |periastron={{val|fmt=commas|2,448,891.649|0.014}} |inclination={{val|53.3|0.5}} }} {{Starbox orbit |reference=<ref name=Torres/> |primary=χ Tau Bab |name=χ Tau Bc |period_unitless={{val|fmt=commas|3,450.6|6.1|u=d}} |k1={{val|8.625|0.067}} |eccentricity={{val|0.3560|0.0068}} |periarg={{val|250.3|1.5}} |periastron={{val|fmt=commas|2,447,546.5|9.7}} |inclination={{val|73|6}} }} {{Starbox detail |age_myr={{val|200|50}}<ref name=Torres/> |component2=χ Tau A |mass2={{val|2.60|0.05}}<ref name=Torres/> |temperature2={{val|fmt=commas|10,300|300}}<ref name=Torres/> |radius2=2.15<ref name=CADARS>{{cite journal|display-authors=1|author1=Pasinetti Fracassini, L. E.|author2=Pastori, L.|author3=Covino, S.|author4=Pozzi, A.|title=Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS) - Third edition - Comments and statistics|journal=Astronomy & Astrophysics|volume=367|issue=2|pages=521–24|date=2001|bibcode=2001A&A...367..521P|doi=10.1051/0004-6361:20000451|arxiv=astro-ph/0012289|s2cid=425754}}</ref> |gravity2=4.15 ± 0.14<ref name=David>{{cite journal|bibcode=2015ApJ...804..146D|doi=10.1088/0004-637X/804/2/146|arxiv=1501.03154|title=The Ages of Early-Type Stars: Strömgren Photometric Methods Calibrated, Validated, Tested, and Applied to Hosts and Prospective Hosts of Directly Imaged Exoplanets|journal=The Astrophysical Journal|volume=804|issue=2|pages=146|year=2015|last1=David|first1=Trevor J.|last2=Hillenbrand|first2=Lynne A.|s2cid=33401607}}</ref> |rotational_velocity2=263<ref name=David/> }} {{Starbox detail|no_heading=y |component1=χ Tau Ba |mass=1.19<ref name=Torres/> |gravity=4.5<ref name=Torres/> |rotational_velocity={{val|1|3}}<ref name=Torres/> |temperature={{val|fmt=commas|6,180|150}}<ref name=Torres/> |component2=χ Tau Bb |mass2=1.02<ref name=Torres/> |gravity2=4.5<ref name=Torres/> |rotational_velocity2={{val|1|3}}<ref name=Torres/> |temperature2={{val|fmt=commas|5,620|150}}<ref name=Torres/> }} {{Starbox detail|no_heading=y |component1=χ Tau Bc |mass=~0.70 / 0.70<ref name=Torres/> }} {{Starbox catalog |names={{odlist|B=χ Tau|F=59 Tau|ADS=3161&nbsp;AB|CCDM=J04226+2538AB|BD=+25°707|HD=27638|HIP=20430|HR=1369|SAO=76573}} }} {{Starbox reference |Simbad=*+chi+Tau|sn=χ Tau A |Simbad2=*+chi+Tau+B|sn2=χ Tau B }} {{Starbox end}}

'''Chi Tauri''', Latinised from '''χ&nbsp;Tauri''', is a star system in the constellation of Taurus. Parallax measurements made by the ''Hipparcos'' spacecraft put it at a distance of about {{Convert|291|ly|pc|abbr=off|lk=on}} from Earth. The primary component has an apparent magnitude of about 5.4,<ref name=TYC2/> meaning it is visible with the naked eye.

The main component of the system is Chi Tauri A. It is a B-type main-sequence star. Its mass is 2.6 times that of the Sun and its surface glows with an effective temperature of {{Val|10300|fmt=commas|ul=K}}. It may be a binary star itself, as suggested from astrometric data from ''Hipparcos'', although no orbit could be derived.<ref name=Torres/>

The secondary component of the system is Chi Tauri B, separated about 19″<ref name=Torres/> from Chi Tauri A. It was thought to be a post-T Tauri star from its unusual spectrum,<ref>{{cite journal|title=A study of visual double stars with early-type primaries. V - Post-T Tauri secondaries|author=Lindroos, K. P.|journal=Astronomy and Astrophysics|volume=156|number=1–2|pages=223–233|date=1986|bibcode=1986A&A...156..223L}}</ref> but later studies ruled this out.<ref name=Torres/> It is a double-lined spectroscopic binary—the two stars are not resolved but their spectra have periodic Doppler shifts indicating orbital motion. The two stars are an F-type star and a G-type star, respectively, and are designated Ba and Bb.<ref name=Torres/>

The radial velocity of Chi Tauri B has a slow drift indicating the presence of another star in the system. Designated Chi Tauri Bc, this massive object is too dim to be detected, but it appears in Chi Tauri B's spectrum as an infrared excess. Because of this infrared excess, this unseen component is thought to be a pair of K-type main-sequence stars both with masses 70% of the Sun's. The stars within the system appear to be dynamically interacting.<ref name=Torres/>

==Naming== *With φ, κ<sup>1</sup>, κ<sup>2</sup> and υ, it composed the Arabic were the Arabs' ''Al Kalbain'', the Two Dogs.<ref name="allen1899">{{cite book | title=Star-Names and Their Meanings | url=https://archive.org/details/in.ernet.dli.2015.42847 | last=Allen | first=Richard Hinckley | author-link=Richard Hinckley Allen | date=1899 | publisher=G. E. Stechert | publication-place=New York | page=413 }}</ref> According to the catalogue of stars in the ''Technical Memorandum 33-507 - A Reduced Star Catalog Containing 537 Named Stars'', ''Al Kalbain'' were the title for five stars: φ as ''Alkalbain I'', this star (χ) as ''Alkalbain II'', κ<sup>1</sup> as ''Alkalbain III'', κ<sup>2</sup> as ''Alkalbain IV'' and υ as ''Alkalbain V''.<ref name=rhoads1971>{{cite journal | url=https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19720005197_1972005197.pdf | first1=Jack W. | last1=Rhoads | title=Technical Memorandum 33-507-A Reduced Star Catalog Containing 537 Named Stars | publisher=Jet Propulsion Laboratory, California Institute of Technology | date=November 15, 1971 }}</ref>{{clarify|this whole note seems to be badly machine-translated|date=June 2020}} *In Chinese, {{lang|zh|礪石}} ({{lang|zh-Latn|Lì Dàn}}), meaning ''Whetstone'', refers to an asterism consisting of χ Tauri, ψ Tauri, 44 Tauri and φ Tauri. Consequently, the Chinese name for χ Tauri itself is {{lang|zh|礪石三}} ({{lang|zh-Latn|Lì Dàn sān}}, {{langx|en|the Third Star of Whetstone}}).<ref>{{cite web |url=http://aeea.nmns.edu.tw/2006/0605/ap060522.html |trans-title=AEEA (Activities of Exhibition and Education in Astronomy) |title=天文教育資訊網 |date=2006-05-22 |language=zh |accessdate=2019-06-20 |archive-date=2011-09-28 |archive-url=https://web.archive.org/web/20110928011211/http://aeea.nmns.edu.tw/2006/0605/ap060522.html |url-status=dead }}</ref>

==References== {{reflist}}

{{Stars of Taurus}}

<!-- Properties --> Category:B-type main-sequence stars Category:F-type main-sequence stars Category:Spectroscopic binaries 5 <!-- Other --> Category:Taurus (constellation) Tauri, Chi BD+25 707 Tauri, 059 027638 020430 1369