Alpha Serpentis
{{Short description|Double star in the constellation Serpens}}
{{Sky|15|44|16.07431|+|06|25|32.2633}}
{{Starbox begin
| name=α Serpentis
}}
{{Starbox image
| image =
{{Location mark
| image=Serpens Caput IAU.svg
| float=center | width=250 | position=right
| mark=Red circle.svg | mark_width=10 | mark_link=π Sco
| x%=47.2 | y%=52.6
}}
| caption=Location of α Serpentis (circled)
}}
{{Starbox observe
| epoch = J2000
| dec = {{DEC|+06|25|32.2633}}
| constell = Serpens
}}
{{Starbox character
| class = {{nowrap|K2 IIIb CN1}}
| variable =
|type=Horizontal branch}}
{{Starbox astrometry
| parallax = 44.10
| p_error = 0.19
| absmag_v = {{val|+0.88|0.03}}
}}
{{Starbox detail
| temperature = {{val|4687|59|fmt=commas}}
}}
{{Starbox catalog
| names = {{odlist | name=Unukalhai | name2=Cor Serpentis | B=Alpha Ser, α Ser | F=24 Serpentis | HR=5854 | HD=140573 | SAO=121157 | HIP=77070 | BD=+06°3088 | ADS=9765 | CCDM=15442+0626 }}
}}
{{Starbox reference
|Simbad=alf+Ser
}}
{{Starbox end}}
Alpha Serpentis or α Serpentis, formally named Unukalhai ({{IPAc-en|,|juː|n|@|k|.|æ|l|'|h|ei}}),{{cite book
|last1=Kunitzsch |first1=Paul
|last2=Smart |first2=Tim
|date = 2006 |edition = 2nd rev.
|title = A Dictionary of Modern star Names: A Short Guide to 254 Star Names and Their Derivations
|publisher = Sky Pub |location = Cambridge, Massachusetts
|isbn = 978-1-931559-44-7
}}{{cite web | url=http://www.pas.rochester.edu/~emamajek/WGSN/IAU-CSN.txt | title=IAU Catalog of Star Names |access-date=28 July 2016}} is a double star in the head (Serpens Caput) of the equatorial constellation of Serpens. With an apparent visual magnitude of 2.6, this star is the brightest in the constellation and it can be viewed with the naked eye from most of the Earth. Parallax measurements yield an estimated distance of about {{Convert|74|ly|pc|abbr=off|lk=on}} from the Sun.
Properties
Alpha Serpentis is a giant star with a stellar classification of K2IIIbCN1, having consumed the hydrogen at its core and evolved away from the main sequence. It has 1.6 times the mass and 13.5 times the radius of the Sun. It is most likely a horizontal branch or red clump star, fusing helium into carbon and heavier elements within its core. The effective temperature of the outer envelope is 4,687 K, giving it an orange hue that is characteristic of a K-type star. It has been classified as a strong CN star, showing a higher than expected strength in the cyanogen bands.
This star is radiating about 30 times the luminosity of the Sun, while a further 32 times the Sun's luminosity is being emitted in the infrared, for 70-fold total. A magnitude +11.8 companion is at an angular separation of 58 arcseconds from Alpha Serpentis, while a 13th magnitude star lies 2.3 arcminutes distant.
Nomenclature
α Serpentis (Latinised to Alpha Serpentis) is the system's Bayer designation.
It bore the traditional names Unukalhai (alternatively spelt Unuk al Hay or Unuk Elhaija) from the Arabic عنق الحيّة ʽunuq al-ḥayyah "the serpent's neck", and Cor Serpentis from the Latin "the Heart of the Serpent". In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN){{citation
| url=https://www.iau.org/science/scientific_bodies/working_groups/280/
| title=IAU Working Group on Star Names (WGSN)
| publisher=International Astronomical Union
| access-date=22 May 2016 | postscript=. }} to catalogue and standardize proper names for stars. The WGSN approved the name Unukalhai for this star on 21 August 2016 and it is now so entered in the IAU Catalog of Star Names.
Alpha Serpentis is a member of the indigenous Arabic asterism al-Nasaq al-Yamānī "the Southern Line" of al-Nasaqān "the Two Lines", along with Delta Serpentis, Epsilon Serpentis, Delta Ophiuchi, Epsilon Ophiuchi, Zeta Ophiuchi and Gamma Ophiuchi. According to a 1971 NASA catalogue, al-Nasaq al-Yamānī or Nasak Yamani was the name for two stars: Delta Serpentis as Nasak Yamani I and Epsilon Serpentis as Nasak Yamani II.[https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19720005197_1972005197.pdf Jack W. Rhoads - Technical Memorandum 33-507-A Reduced Star Catalog Containing 537 Named Stars, Jet Propulsion Laboratory, California Institute of Technology; November 15, 1971]
In Chinese, {{lang|zh|天市右垣}} ({{lang|zh-Latn|Tiān Shì Yòu Yuán}}), meaning Right Wall of Heavenly Market Enclosure, refers to an asterism which represents eleven old states in China and which is marking the right borderline of the enclosure, consisting of Alpha Serpentis, Beta Herculis, Gamma Herculis, Kappa Herculis, Gamma Serpentis, Beta Serpentis, Delta Serpentis, Epsilon Serpentis, Delta Ophiuchi, Epsilon Ophiuchi and Zeta Ophiuchi.{{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 Alpha Serpentis itself is {{lang|zh|天市右垣七}} ({{lang|zh-Latn|Tiān Shì Yòu Yuán qī}}, {{langx|en|the Seventh Star of Right Wall of Heavenly Market Enclosure}}), and represents the state Shu (蜀) (or Shuh){{in lang|zh}} [http://www.lcsd.gov.hk/CE/Museum/Space/Research/StarName/c_research_chinengstars_t_z.htm 香港太空館 - 研究資源 - 亮星中英對照表] {{webarchive|url=https://web.archive.org/web/20100819122914/http://www.lcsd.gov.hk/CE/Museum/Space/Research/StarName/c_research_chinengstars_t_z.htm |date=2010-08-19 }}, Hong Kong Space Museum. Accessed on line November 23, 2010.{{in lang|zh}} [http://www.lcsd.gov.hk/CE/Museum/Space/Research/StarName/e_research_chinengstarzone_b.htm#HeavenlyMarketEnclosure English-Chinese Glossary of Chinese Star Regions, Asterisms and Star Name] {{webarchive|url=https://web.archive.org/web/20080924022136/http://www.lcsd.gov.hk/CE/Museum/Space/Research/StarName/e_research_chinengstarzone_b.htm |date=2008-09-24 }}, Hong Kong Space Museum. Accessed on line November 23, 2010. (together with Lambda Serpentis in R.H.Allen's works).
References
{{Reflist|30em|refs=
| title=A Recipe for Finding Stellar Radii, Temperatures, Surface Gravities, Metallicities, and Masses Using Spectral Lines
| last1=Gray | first1=David F. | last2=Kaur | first2=Taranpreet
| journal=The Astrophysical Journal
| volume=882 | issue=2 | id=148 | pages=16 | date=September 2019
| doi=10.3847/1538-4357/ab2fce | bibcode=2019ApJ...882..148G | s2cid=203078143 | doi-access=free }}
| title=Recognition and classification of strong-CN giants
| display-authors=1 | last1=Keenan | first1=Philip C.
| last2=Yorka | first2=Sandra B. | last3=Wilson | first3=Olin C.
| journal=Publications of the Astronomical Society of the Pacific
| volume=99 | pages=629–636 | date=July 1987
| doi=10.1086/132025 | bibcode=1987PASP...99..629K | doi-access=free }}
| last1=Keenan | first1=Philip C. | last2=McNeil | first2=Raymond C.
| title=The Perkins catalog of revised MK types for the cooler stars
| journal=Astrophysical Journal Supplement Series
| volume=71 | pages=245 | year=1989
| bibcode=1989ApJS...71..245K | doi=10.1086/191373 }}
{{citation | title=UNUKALHAI -- Star in double system | work=SIMBAD | publisher=Centre de Données astronomiques de Strasbourg | url=http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=Beta+Pyx | access-date=2012-01-11 }}
{{citation | first1=James B. | last1=Kaler | title=UNUKALHAI (Alpha Serpentis) | work=Stars | publisher=University of Illinois | url=http://stars.astro.illinois.edu/sow/unukalhai.html | access-date=2012-01-11 }}
{{citation|title=The Colour of Stars |date=December 21, 2004 |work=Australia Telescope, Outreach and Education |publisher=Commonwealth Scientific and Industrial Research Organisation |url=http://outreach.atnf.csiro.au/education/senior/astrophysics/photometry_colour.html |access-date=2012-01-16 |url-status=dead |archive-url=https://web.archive.org/web/20120222183238/http://outreach.atnf.csiro.au/education/senior/astrophysics/photometry_colour.html |archive-date=February 22, 2012 }}
}}
{{Stars of Serpens}}
{{DEFAULTSORT:Alpha Serpentis}}