theta Eridani

{{Starbox image

| image =

{{Location mark

| image=Eridanus constellation map.svg

| float=center | width=250 | position=right

| mark=Red circle.svg | mark_width=10 | mark_link=θ Eri

| x%=67.4 | y%=66.6

}}

| caption = Location of θ Eridani (circled)

}}

{{Starbox observe 2s

| component1 = θ¹ Eri

| constell = Eridanus

| epoch = J2000

| ra1 = {{RA|02|58|15.6764}}

| dec1 = {{DEC|−40|18|16.839}}

| appmag_v1 = 3.18

| component2 = θ² Eri

| ra2 = {{RA|02|58|16.4037}}

| dec2 = {{DEC|−40|18|16.906}}

| appmag_v2 = 4.11

}}

{{Starbox character

| component1 = θ¹ Eri

| class = A3IV-V

| b-v = {{val|+0.128|0.012}}

| u-b = +0.14

| component2 = θ² Eri

| class2 = A1V

| b-v2 = +0.08

| u-b2 =

| variable2 = suspected

}}

{{Starbox astrometry

| component1 = θ¹ Eri

| radial_v = {{val|+11.9|2.6}}

| prop_mo_ra = −57.132

| prop_mo_dec = +23.058

| parallax = 19.9047

| p_error = 0.2062

| parallax_footnote =

| absmag_v =

| component2 = θ² Eri

| prop_mo_ra2 = −50.502

| prop_mo_dec2 = +16.613

| parallax2 = 19.5270

| p_error2 = 0.1372

| parallax_footnote2 =

| absmag_v2 = −0.59 (combined)

}}

{{Starbox detail

| component1 = θ¹ Eri

| mass = 2.6

| radius ={{Solar radius calculator|type=LT|96|8200|decimals=2}}{{Efn|Retrieved from a luminosity of 96 {{Solar luminosity|link=y}} and a temperature of 8200 K|name=Temperature and luminosity}}

| luminosity = 96

| temperature = 8,200

| rotational_velocity = 65.1

| rotation =

| component2 = θ² Eri

| mass2 = 1.95

| radius2 = 2.7

| luminosity2 = 37

| temperature2 = 8,293

| gravity2 = 3.83

| metal2_fe = −0.197

| rotational_velocity2 = 102.5

}}

{{Starbox catalog

| names = {{odlist | B=Theta Eri, θ Eri | HIP=13847 | CCDM=J02583-4018 | CD=−40° 771 | SAO=216113 | WDS=02583-4018 }}

| component1=θ¹ Eri

| names1 = {{odlist | HD=18622 | HR=897 | name=Acamar}}

| component2=θ² Eri

| names2 = {{odlist | HD=18623 | HR=898 }}

}}

{{Starbox reference

| Simbad=HD+18622|sn=θ¹ Eri

| Simbad2=HD+18623|sn2=θ² Eri

}}

Theta Eridani, Latinized from θ Eridani, is a binary system in the constellation of Eridanus with a combined apparent magnitude of 2.88. Its two components are designated θ¹ Eridani, formally named Acamar {{IPAc-en|'|æ|k|@|m|ɑr}} (the traditional name of the system),{{cite journal

|title=Star Name Pronunciation

|last=Rumrill |first=H. B.

|journal=Publications of the Astronomical Society of the Pacific

|volume=48

|number=283

|date=June 1936

|page=139 |location = San Francisco, California

|doi=10.1086/124681

|bibcode=1936PASP...48..139R |s2cid=120743052 |doi-access=free

}}{{cite web | url=http://www.pas.rochester.edu/~emamajek/WGSN/IAU-CSN.txt | title=IAU Catalog of Star Names |access-date=28 July 2016}} and θ² Eridani. The system's distance from the Sun based on parallax measurements is approximately 165 light-years.

Nomenclature

Theta Eridani is the system's Bayer designation; θ¹ and θ² Eridani those of its two components.

The system bore the traditional name Acamar, derived from the Arabic آخِر النَّهْر {{citation needed|date=June 2013}} Ākhir an-nahr, which means "the end of the river", via a Roman-alphabet handwriting misread "rn" to "m". In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN){{cite web | url=https://www.iau.org/science/scientific_bodies/working_groups/280/ | title=IAU Working Group on Star Names (WGSN)|access-date=22 May 2016}} to catalog and standardize proper names for stars. The WGSN decided to attribute proper names to individual stars rather than entire multiple systems.{{cite web | url=https://www.iau.org/static/science/scientific_bodies/working_groups/280/wg-starnames-triennial-report-2015-2018.pdf | page=5 | title=WG Triennial Report (2015-2018) - Star Names |access-date=2018-07-14}} It approved the name "Acamar" for θ¹ Eridani on 20 July 2016 and it is now so entered in the IAU Catalog of Star Names.

The term "Ākhir an-nahr", or "Achr al Nahr", appeared in the catalogue of stars in the Calendarium of Al Achsasi Al Mouakket, which was translated into Latin as Postrema Fluminis.{{cite journal

| last=Knobel | first=E. B.

| title=Al Achsasi Al Mouakket, on a catalogue of stars in the Calendarium of Mohammad Al Achsasi Al Mouakket

| journal=Monthly Notices of the Royal Astronomical Society

| volume=55 | page=429 |date=June 1895

| bibcode=1895MNRAS..55..429K | doi=10.1093/mnras/55.8.429| doi-access=free}}

Historically, Acamar represented the end of the constellation Eridanus.{{cite journal | author=Rogers, J. H. | title=Origins of the ancient constellations: II. The Mediterranean traditions | journal=Journal of the British Astronomical Association| date=1998 | volume=108| issue = 2 | pages=79–89 | bibcode=1998JBAA..108...79R}} Now that distinction is held by the star Achernar, which shares the same Arabic etymology. Achernar is not visible from the Greek isles (latitudes > 33° North),{{cite web |title=Achernar: End of the River |publisher=EarthSky Tonight Post 06-29-2009 |author=Larry Sessions |url=http://www.earthsky.org/tonightpost/brightest-stars/bright-achernar-ends-the-southern-river |access-date=2010-02-26}} hence the choice of Acamar as the river's end during the time of Hipparchus and, later, Ptolemy.

In Chinese, {{lang|zh|天園}} ({{lang|zh-Latn|Tiān Yuán}}), meaning Celestial Orchard, refers to an asterism consisting of Theta Eridani, Chi Eridani, Phi Eridani, Kappa Eridani, HD 16754, HD 23319, HD 24072, HD 24160, Upsilon⁴ Eridani, Upsilon³ Eridani, Upsilon² Eridani and Upsilon¹ Eridani.{{in lang|zh}} 中國星座神話, written by 陳久金. Published by 台灣書房出版有限公司, 2005, {{ISBN|978-986-7332-25-7}}. Consequently, the Chinese name for Theta Eridani itself is {{lang|zh|天園六}} ({{lang|zh-Latn|Tiān Yuán liù}}, {{langx|en|the Sixth Star of Celestial Orchard}}).{{in lang|zh}} [http://www.lcsd.gov.hk/CE/Museum/Space/Research/StarName/c_research_chinengstars_a_al.htm 香港太空館 - 研究資源 - 亮星中英對照表] {{webarchive|url=https://web.archive.org/web/20100903162121/http://www.lcsd.gov.hk/CE/Museum/Space/Research/StarName/c_research_chinengstars_a_al.htm |date=2010-09-03 }}, Hong Kong Space Museum. Accessed on line November 23, 2010.

Stellar system

Theta Eridani is a binary system with some evidence suggesting it is part of a multiple star system.NSV 01002, database entry, [http://www.sai.msu.su/groups/cluster/gcvs/gcvs/nsv/nsv.dat New Catalogue of Suspected Variable Stars, the improved version], Sternberg Astronomical Institute, Moscow, Russia. Accessed on line February 26, 2010.{{cite web |url=http://www.alcyone.de/SIT/mainstars/SIT000436.htm#Cat6 | title=Acamar | publisher=Alcyone Bright Star Catalogue | access-date=2010-02-26 }} The main star, θ¹ Eridani, is of spectral class A4 with a +3.2 apparent magnitude. Its companion star, θ² Eridani, is of spectral class A1 with an apparent magnitude of +4.1. The angular separation of the two stars is equal to 8.3 arcseconds.

Notes

References

{{reflist|30em|refs=

{{cite journal |last1=Anders |first1=F. |last2=Khalatyan |first2=A. |last3=Chiappini |first3=C. |last4=Queiroz |first4=A. B. |last5=Santiago |first5=B. X. |last6=Jordi |first6=C. |last7=Girardi |first7=L. |last8=Brown |first8=A. G. A. |last9=Matijevič |first9=G. |last10=Monari |first10=G. |last11=Cantat-Gaudin |first11=T. |last12=Weiler |first12=M. |last13=Khan |first13=S. |last14=Miglio |first14=A. |last15=Carrillo |first15=I. |last16=Romero-Gómez |first16=M. |last17=Minchev |first17=I. |last18=de Jong |first18=R. S. |last19=Antoja |first19=T. |last20=Ramos |first20=P. |last21=Steinmetz |first21=M. |last22=Enke |first22=H. |title=Photo-astrometric distances, extinctions, and astrophysical parameters for Gaia DR2 stars brighter than G = 18 |journal=Astronomy & Astrophysics |date=August 2019 |volume=628 |pages=A94 |doi=10.1051/0004-6361/201935765 |issn=0004-6361 |bibcode=2019A&A...628A..94A |arxiv=1904.11302 |doi-access=free}}

{{citation

| title=Contributions to the Nearby Stars (NStars) Project: Spectroscopy of Stars Earlier than M0 within 40 pc-The Southern Sample

| last1=Gray | first1=R. O. | last2=Corbally | first2=C. J.

| last3=Garrison | first3=R. F. | last4=McFadden | first4=M. T.

| last5=Bubar | first5=E. J. | last6=McGahee | first6=C. E.

| last7=O'Donoghue | first7=A. A. | last8=Knox | first8=E. R.

| display-authors=1 | postscript=.

| journal=The Astronomical Journal

| volume=132 | issue=1 | pages=161–170 | year=2006

| doi=10.1086/504637 | arxiv=astro-ph/0603770

| bibcode=2006AJ....132..161G | s2cid=119476992 }}

{{citation

| title=XHIP: An extended hipparcos compilation

| last1=Anderson | first1=E. | last2=Francis | first2=Ch.

| journal=Astronomy Letters

| volume=38 | issue=5 | pages=331 | year=2012

| bibcode=2012AstL...38..331A | doi=10.1134/S1063773712050015

| arxiv=1108.4971 | s2cid=119257644 | postscript=. }}

{{cite web

| title=Bright Star Catalogue

| edition=5th Revised

| author=Hoffleit

| display-authors=etal

| date=1991

| work=VizieR

| publisher=Centre de Données astronomiques de Strasbourg

| url=http://vizier.u-strasbg.fr/viz-bin/VizieR-S?HR%20897

| access-date=2010-02-24 }}

{{cite web

| title=ACAMAR (Theta Eridani)

| publisher=University of Illinois | work=Stars

| first1=James B. | last1=Kaler

| url=http://stars.astro.illinois.edu/sow/acamar.html

| access-date=2010-02-24 }}

{{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=De Lee|first6=Nathan|last7=Collins|first7=Kevin|last8=Latham|first8=David W.|last9=Muirhead|first9=Philip S.|last10=Chittidi|first10=Jay|last11=Rojas-Ayala|first11=Bárbara|date=2019-10-01|title=The Revised TESS Input Catalog and Candidate Target List|bibcode=2019AJ....158..138S|journal=The Astronomical Journal|volume=158|issue=4|pages=138|doi=10.3847/1538-3881/ab3467|arxiv=1905.10694 |hdl=1721.1/124721|s2cid=166227927|issn=0004-6256|hdl-access=free |doi-access=free }}

{{cite journal

| display-authors=1

| last1=Díaz | first1=C. G. | last2=González | first2=J. F.

| last3=Levato | first3=H. | last4=Grosso | first4=M.

| title=Accurate stellar rotational velocities using the Fourier transform of the cross correlation maximum

| journal=Astronomy & Astrophysics

| volume=531 | page=A143 |date=July 2011

| doi=10.1051/0004-6361/201016386 | bibcode=2011A&A...531A.143D

| arxiv=1012.4858 | s2cid=119286673 }}

{{cite journal |last1=Ammler-von Eiff |first1=M. |last2=Reiners |first2=A. |title=New measurements of rotation and differential rotation in A-F stars: are there two populations of differentially rotating stars? |journal=Astronomy & Astrophysics |date=June 2012 |volume=542 |pages=A116 |doi=10.1051/0004-6361/201118724 |issn=0004-6361 |bibcode=2012A&A...542A.116A |arxiv=1204.2459 |doi-access=free}}

{{cite journal |last1=Fabricius |first1=C. |last2=Høg |first2=E. |last3=Makarov |first3=V. V. |last4=Mason |first4=B. D. |last5=Wycoff |first5=G. L. |last6=Urban |first6=S. E. |title=The Tycho double star catalogue |journal=Astronomy and Astrophysics |date=1 March 2002 |volume=384 |pages=180–189 |doi=10.1051/0004-6361:20011822 |bibcode=2002A&A...384..180F |issn=0004-6361 |doi-access=free }}

}}

Category:A-type main-sequence stars

Category:Eridanus (constellation)