{{Short description|Variable star in the constellation Hercules}} {{Starbox begin | name = o Herculis }} {{Starbox image | image= {{Location mark |image=Hercules constellation map.svg|alt=|float=center|width=260 |label=|position=right |mark=Red circle.svg|mark_width=10|mark_link=o Herculis |x=328|y=576 }} |caption=Location of o Herculis (circled) }} {{Starbox observe | epoch = J2000 | ra = {{RA|18|07|32.55073}}<ref name=aaa474_2_653/> | dec = {{DEC|+28|45|44.9679}}<ref name=aaa474_2_653/> | appmag_v = 3.83<ref name=clpl4_99/> | constell = Hercules }} {{Starbox character | class = B9.5III<ref name=Slettebak1982/> | r-i = | v-r = | b-v = −0.02<ref name=clpl4_99/> | u-b = −0.07<ref name=clpl4_99/> | variable = γ Cas<ref name=Samus2017/> }} {{Starbox astrometry | radial_v = −29.5<ref name=gcsrv/> | prop_mo_ra = −0.02<ref name=aaa474_2_653/> | prop_mo_dec = +8.55<ref name=aaa474_2_653/> | parallax = 9.65 | p_error = 0.16 | parallax_footnote = <ref name=aaa474_2_653/> | absmag_v = −1.24<ref name=Anderson2012/> }} {{Starbox detail | source = | mass = {{Val|3.49|0.04}}<ref name=Zorec2012/> | radius = 6.3<ref name=ticv8/> | luminosity = 355 | temperature = 9,484<ref name=ticv8/> | metal_fe = −0.06<ref name=Anderson2012/> | gravity = 2.86<ref name=starhorse/> | rotational_velocity = 194<ref name=aaa463_2_671/> | age_gyr = }} {{Starbox catalog | names = o&nbsp;Her, 103 Herculis, BD+28 2925, FK5 681, HD 166014, HIP 88794, HR 6779, SAO 85750 }} {{Starbox reference |Simbad=omi+Her }} {{Starbox end}} '''Omicron Herculis''', Latinized from o Herculis, is a star in the constellation Hercules.

== Nomenclature == This star used to be called Masym (from Arabic for "the wrist"), but this name was transferred to Lambda Herculis.<ref name=kaler/><ref name=allen1899/>

In Chinese astronomy, this is the fourth star of the asterism ''Tiān Shì Zuǒ Yuán'' ({{lang|zh|天市左垣}}, Left Wall of Heavenly Market Enclosure), representing the state Zhongshan ({{lang|zh|中山}}).<ref name=AEEA/> In R. H. Allen's book ''Star Names'' this name, transliterated as ''Chung Shan'' with the meaning "the Middle Mountain", was instead attributed to ν Her, ξ Her, and 99 (b) Her.<ref name=allen1899/>

== Properties == Omicron Herculis is a B9.5III star approximately 106 pc from the Earth. It has an apparent magnitude of 3.83. The star radiates with a bluish-white hue, and has a luminosity approximately 355 times as bright as the Sun. Omicron Herculis is 3.49 solar masses.<ref name=Zorec2012/> Stellar evolutionary caclulations show that it has just left the main sequence.<ref name=Zorec2012/>

Omicron Herculis is an eruptive variable of the Gamma Cassiopeiae class,<ref name=Samus2017/> which are rapidly rotating B-class stars with mass outflow. It has a projected rotational velocity of 194&nbsp;km/s.<ref name=aaa463_2_671/>

Some sources list Omicron Herculis as being both spectroscopic and an interferometric binary star with a separation of about 60 milliarcseconds, although the companion star has not been confirmed.<ref name=Hutter/>

Omicron Hercules is notable for residing close to the coordinates of the solar apex, the direction towards which the Sun is moving. This was first noticed by William Herschel in 1783,<ref name=lankford97/> although in his first calculation he identified this point with Lambda Herculis.<ref name=herschel/> It will eventually become the brightest star in the night sky in approximately 3.47 million years from today, at –0.63,<ref name=tomkin1998 /> slightly less bright than Canopus today.<ref name=tomkin1998/>

== References == <references> <ref name=kaler>{{cite web |title=Omicron Herculis |first=Jim|last=Kaler |url=http://stars.astro.illinois.edu/sow/omiher.html |access-date=2016-05-13}}</ref>

<ref name=tomkin1998>{{cite journal|last=Tomkin|first=Jocelyn|date=April 1998|title=Once and Future Celestial Kings|journal=Sky and Telescope|volume=95|issue=4|pages=59–63|bibcode=1998S&T....95d..59T}} – based on computations from HIPPARCOS data. (The calculations exclude stars whose distance or proper motion is uncertain.) [ftp://tlgleonid.asuscomm.com/HITACHI/BOOK_ASTRO/S&T/SkyandTelescope_1998%20-%20astronomy/04/199804059063.pdf PDF]{{dead link|date=May 2025|bot=medic}}{{cbignore|bot=medic}}</ref>

<ref name=herschel>{{cite journal |jstor=106492 |last1=Herschel |first1=William |author-link=William Herschel |date=1783 |title=On the Proper Motion of the Sun and Solar System; With an Account of Several Changes That Have Happened among the Fixed Stars since the Time of Mr. Flamstead [sic] |journal=Philosophical Transactions of the Royal Society of London |volume=73 |pages=247–83 |doi=10.1098/rstl.1783.0017 |s2cid=186213288 }}</ref>

<ref name=Hutter>{{cite journal | title=Surveying the Bright Stars by Optical Interferometry. III. A Magnitude-limited Multiplicity Survey of Classical Be Stars | year=2021 | last1=Hutter | first1=D. J. | last2=Tycner | first2=C. | last3=Zavala | first3=R. T. | last4=Benson | first4=J. A. | last5=Hummel | first5=C. A. | last6=Zirm | first6=H. | journal=The Astrophysical Journal Supplement Series | volume=257 | issue=2 | page=69 | doi=10.3847/1538-4365/ac23cb | arxiv=2109.06839 | bibcode=2021ApJS..257...69H | s2cid=237503492 | doi-access=free }}</ref>

<ref name=starhorse>{{cite journal |display-authors=1 |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}}</ref>

<ref name=ticv8>{{citation |postscript=.|author=Stassun K.G.|s2cid=166227927|display-authors=etal|date=October 2019|title=The revised TESS Input Catalog and Candidate Target List|journal=The Astronomical Journal|volume=158|issue=4|page=138|arxiv=1905.10694|bibcode=2019AJ....158..138S|doi=10.3847/1538-3881/ab3467 |doi-access=free }}</ref>

<ref name=aaa474_2_653>{{citation | last1=van Leeuwen | first1=F. | title=Validation of the new Hipparcos reduction | journal=Astronomy and Astrophysics | volume=474 | issue=2 |date=November 2007 | pages=653–664 | doi=10.1051/0004-6361:20078357 | bibcode=2007A&A...474..653V | arxiv=0708.1752 | s2cid=18759600 | postscript=. }}</ref>

<ref name=Slettebak1982>{{citation | last1=Slettebak | first1=A. | title=Spectral types and rotational velocities of the brighter Be stars and A-F type shell stars | journal=Astrophysical Journal Supplement Series | volume=50 | pages=55 | year=1982 | postscript=. | bibcode=1982ApJS...50...55S | doi=10.1086/190820 | doi-access=free }}</ref>

<ref name=Anderson2012>{{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=. }}</ref>

<ref name=Zorec2012>{{citation | last1=Zorec | first1=J. | last2=Royer | first2=F. | title=Rotational velocities of A-type stars. IV. Evolution of rotational velocities | journal=Astronomy & Astrophysics | volume=537 | pages=A120 | year=2012 | bibcode=2012A&A...537A.120Z | doi=10.1051/0004-6361/201117691 | arxiv=1201.2052 | s2cid=55586789 | postscript=. }}</ref>

<ref name=Samus2017>{{citation | display-authors=1 | last1=Samus | first1=N. N. | last2=Kazarovets | first2=E. V. | last3=Durlevich | first3=O. V. | last4=Kireeva | first4=N. N. | last5=Pastukhova | first5=E. N. | title=General Catalogue of Variable Stars | version=GCVS 5.1 | journal=Astronomy Reports | year=2017 | volume=61 | issue=1 | pages=80–88 | bibcode=2017ARep...61...80S | postscript=. |doi = 10.1134/S1063772917010085 | s2cid=125853869 }}</ref>

<ref name=gcsrv>{{citation | last=Wilson | first=Ralph Elmer | year=1953 | title=General Catalogue of Stellar Radial Velocities | journal=Carnegie Institute Washington D.C. Publication | publisher=Carnegie Institution of Washington | location=Washington | bibcode=1953GCRV..C......0W | postscript=. }}</ref>

<ref name=aaa463_2_671>{{citation | last1=Royer | first1=F. | last2=Zorec | first2=J. | last3=Gómez | first3=A. E. | title=Rotational velocities of A-type stars. III. Velocity distributions | journal=Astronomy and Astrophysics | volume=463 | issue=2 | pages=671–682 |date=February 2007 | doi=10.1051/0004-6361:20065224 | bibcode=2007A&A...463..671R |arxiv = astro-ph/0610785 | s2cid=18475298 | postscript=. }}</ref>

<ref name=clpl4_99>{{citation | display-authors=1 | last1=Johnson | first1=H. L. | last2=Iriarte | first2=B. | last3=Mitchell | first3=R. I. | last4=Wisniewskj | first4=W. Z. | title=UBVRIJKL photometry of the bright stars | journal=Communications of the Lunar and Planetary Laboratory | volume=4 | issue=99 | year=1966 | page=99 | bibcode=1966CoLPL...4...99J | postscript=. }}</ref>

<ref name=lankford97>{{citation | postscript=. | first=John | last=Lankford | date=1997 | title=History of astronomy: an encyclopedia | page=[https://archive.org/details/historyofastrono00john/page/258 258] | volume=1 | series=Garland encyclopedias in the history of science | publisher=Taylor & Francis | isbn=0-8153-0322-X | url-access=registration | url=https://archive.org/details/historyofastrono00john/page/258 }}</ref>

<ref name=allen1899>{{citation | first1=R. H. | last1=Allen | title=Star Names: Their Lore and Meaning | date=1899 | url=https://penelope.uchicago.edu/Thayer/E/Gazetteer/Topics/astronomy/_Texts/secondary/ALLSTA/Hercules*.html | page=245 }}</ref>

<ref name=AEEA>{{cite web |title=AEEA 天文教育資訊網 |trans-title=Activities of Exhibition and Education in Astronomy |language=zh |url=http://aeea.nmns.edu.tw/2006/0606/ap060623.html |archive-url=https://web.archive.org/web/20210515003305/http://aeea.nmns.edu.tw/2006/0606/ap060623.html |archive-date=15 May 2021 |url-status=dead}}</ref> </references>

==External links== * http://www.alcyone.de/SIT/bsc/HR6779.html

{{Stars of Hercules}}

{{DEFAULTSORT:Omicron Herculis}} Category:Hercules (constellation) Herculis, Omicron Herculis, 103 Category:B-type giants 088794 6779 BD+28 2925 166014