Eta Piscium
{{short description|Binary star system in the constellation Pisces}}
{{Starbox begin
| name = Eta Piscium
}}
{{Starbox image
| image =
{{Location mark
| image=Pisces IAU.svg | alt= | float=center | width=250
| label= | position=right
| mark=Red circle.svg | mark_width=10 | mark_link=η Psc
| x=330 | y=375
}}
| caption=Location of η Piscium (circled)
}}
{{Starbox observe
| epoch = J2000.0
| constell = Pisces
| dec = {{DEC|+15|20|44.9685}}
| appmag_v = +3.611 {{nowrap|(3.83 + 7.51)}}
}}
{{Starbox character
| variable = γ Cas
}}
{{Starbox astrometry
| radial_v = {{Val|13.60|0.42}}
| parallax = 9.33
| p_error = 0.72
}}
{{Starbox orbit
| period = {{Val|850.5|66.5}}
| axis = {{Val|1.228|0.144}}
| eccentricity = {{Val|0.469|0.053}}
| inclination = {{Val|58.5|2.5}}
| node = {{Val|32.8|2.0 }}
| periastron = {{Val|2040.3|66.9}}
| periarg = {{Val|86.9|4.0}}
}}
{{Starbox detail
| component1 = η Psc A
| mass = {{Val|3.78|0.16}}
| radius = {{Val|26.48|2.15}}
| luminosity = 457
| gravity = {{Val|2.20|0.14}}
| temperature = {{Val|4937|40|fmt=commas}}
| metal_fe = {{Val|−0.13|0.06}}
| age_myr = {{Val|220|30}}
}}
{{Starbox catalog
| names = Alpherg, {{odlist | B=η Psc | F=99 Piscium | BD=+14°231 | FK5=50 | HD=9270 | HIP=7097 | HR=437 | SAO=92484 | WDS=J01315+1521AB }}
}}
{{Starbox reference
| Simbad = eta+Psc
}}
{{Starbox end}}
Eta Piscium (η Piscium, abbreviated Eta Psc, η Psc) is a binary star and the brightest star in the constellation of Pisces, with an apparent visual magnitude of +3.6. Based upon a measured annual parallax shift of 9.33 mas as seen from Earth, it is located roughly 350 light-years distant from the Sun in the thin disk population of the Milky Way.
The two components are designated Eta Piscium A (formally named Alpherg {{IPAc-en|'|æ|l|f|3r|g}}, the traditional name of the system){{cite web | url=https://www.iau.org/public/themes/naming_stars/ | title=Naming Stars |publisher=IAU.org |access-date=18 June 2018}} and B.
Nomenclature
η Piscium (Latinised to Eta Piscium) is the system's Bayer designation. The designations of the two constituents as Eta Piscium A and B derive from the convention used by the Washington Multiplicity Catalog (WMC) for multiple star systems, and adopted by the International Astronomical Union (IAU).{{cite arXiv |title=On the naming convention used for multiple star systems and extrasolar planets |date=2010 |eprint=1012.0707 |class=astro-ph.SR |last1= Hessman |first1=F. V. |last2= Dhillon |first2=V. S. |last3= Winget |first3=D. E. |last4= Schreiber |first4=M. R. |last5= Horne |first5=K. |last6= Marsh |first6=T. R. |last7= Guenther |first7=E. |last8= Schwope |first8=A. |last9= Heber |first9=U. }}
The system bore the traditional names Al Pherg (in this context meaning the emptying) and Kullat Nunu. At the time that the Sun at the March Equinox entered into Pisces having lay in Aries, the system was in the first ecliptic constellation of the Neo-Babylonians, Kullat Nūnu − Nūnu being Babylonian for fish and Kullat referring to either the bucket or the cord that binds the fish. In 2016, the IAU 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 Alpherg for the component Eta Piscium A on 1 June 2018 (for its official List).
In Chinese, {{lang|zh|右更}} ({{lang|zh-Latn|Yòu Gèng}}), meaning Official in Charge of the Pasturing, refers to an asterism consisting of Eta Piscium, Rho Piscium, Pi Piscium, Omicron Piscium and 104 Piscium. Consequently, the Chinese name for Eta Piscium itself is {{lang|zh|右更二}} ({{lang|zh-Latn|Yòu Gèng èr}}, {{langx|en|the Second Star of Official in Charge of the Pasturing}}.){{in lang|zh}} [http://aeea.nmns.edu.tw/2006/0605/ap060519.html AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 5 月 19 日] {{Webarchive|url=https://web.archive.org/web/20160303170659/http://aeea.nmns.edu.tw/2006/0605/ap060519.html |date=2016-03-03 }}
Properties
At its present distance, the visual magnitude of the system is diminished by an extinction factor of {{Val|0.09|0.06}} due to interstellar dust.
This system's binary nature was discovered in 1878 by an amateur astronomer, S. W. Burnham. It has an orbital period of roughly 850 years, a semimajor axis of 1.2 arc seconds, and an eccentricity of 0.47.
The primary, component A, is an evolved, magnitude 3.83 G-type giant star with a stellar classification of G7 IIIa. It has a weak magnetic field with a strength of {{Val|0.4|0.2|ul=G}}, and is a Gamma Cassiopeiae variable. The companion, component B, is a magnitude 7.51 star.
References
{{reflist|refs=
| title=Validation of the new Hipparcos reduction
| last1=van Leeuwen | first1=F.
| journal=Astronomy and Astrophysics
| volume=474 | issue=2 | pages=653–664 | date=2007
| arxiv=0708.1752 | bibcode=2007A&A...474..653V
| doi=10.1051/0004-6361:20078357 | s2cid=18759600 | postscript=. }}
| 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=. }}
| title=Eight new and three recalculated orbits for binaries
| last1=Cvetković | first1=Z. | last2=Novaković | first2=B.
| journal=Astronomische Nachrichten | date=March 2010
| volume=331 | issue=3 | page=304 | postscript=.
| doi=10.1002/asna.200911250 | bibcode=2010AN....331..304C }}
| 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
| volume=389 | issue=2 | pages=869–879 | date=September 2008
| doi=10.1111/j.1365-2966.2008.13596.x | doi-access=free | bibcode=2008MNRAS.389..869E
| arxiv=0806.2878 | s2cid=14878976 | postscript=.}}
| title=The magnetic fields at the surface of active single G-K giants
| last1=Aurière | first1=M. | last2=Konstantinova-Antova | first2=R.
| last3=Charbonnel | first3=C. | last4=Wade | first4=G. A.
| last5=Tsvetkova | first5=S. | last6=Petit | first6=P.
| last7=Dintrans | first7=B. | last8=Drake | first8=N. A.
| last9=Decressin | first9=T. | last10=Lagarde | first10=N.
| last11=Donati | first11=J. F. | last12=Roudier | first12=T.
| last13=Lignières | first13=F. | last14=Schröder | first14=K. P.
| last15=Landstreet | first15=J. D. | last16=Lèbre | first16=A.
| last17=Weiss | first17=W. W. | last18=Zahn | first18=J. P.
| journal=Astronomy & Astrophysics | arxiv=1411.6230
| volume=574 | id=A90 | pages=30 | date=February 2015 | postscript=.
| doi=10.1051/0004-6361/201424579 | bibcode=2015A&A...574A..90A | s2cid=118504829 }}
| display-authors=1 | last1=Maldonado | first1=J.
| last2=Villaver | first2=E. | last3=Eiroa | first3=C.
| title=The metallicity signature of evolved stars with planets
| journal=Astronomy & Astrophysics
| volume=554 | id=A84 | pages=18 | date=June 2013
| doi=10.1051/0004-6361/201321082 | bibcode=2013A&A...554A..84M
| arxiv=1303.3418 | s2cid=119289111 | postscript=. }}
| title=UBV photometry of stars whose positions are accurately known. II
| last1=Oja | first1=T.
| journal=Astronomy and Astrophysics Supplement Series
| volume=59 | pages=461–464 | date=March 1985
| bibcode=1985A&AS...59..461O | postscript=. }}
| title=The Perkins catalog of revised MK types for the cooler stars
| journal=Astrophysical Journal Supplement Series
| volume=71 | pages=245 | year=1989 | postscript=.
| last1=Keenan | first1=Philip C. | last2=McNeil | first2=Raymond C.
| bibcode=1989ApJS...71..245K | doi=10.1086/191373 }}
| title=eta Psc | access-date=2017-07-30 }}
| last1=Allen
| first1=Richard Hinckley
| author1-link=Richard Hinckley Allen
| title=Star Names: Their Lore and Meaning
| edition=rep.
| year=1963
| orig-year=1899
| publisher=Dover Publications Inc.
| url=https://archive.org/details/starnamestheirlo00alle/page/328
| isbn=0-486-21079-0
| pages=[https://archive.org/details/starnamestheirlo00alle/page/328 328–29]
| url-access=registration
}}
}}
External links
- {{citation
| first1=James B. | last1=Kaler | work=Stars
| title=KULLAT NUNU (Eta Piscium) | publisher=University of Illinois
| url=http://stars.astro.illinois.edu/sow/kullatnunu.html
| access-date=2017-07-30 | postscript=. }}
{{Stars of Pisces|state=collapsed}}
{{DEFAULTSORT:Eta Piscium}}
Category:Gamma Cassiopeiae variable stars
Category:Pisces (constellation)