View source for 70 Ophiuchi

{{Short description|Star in the constellation Ophiuchus}}
{{about-distinguish|p Ophiuchi|Rho Ophiuchi{{!}}ρ (Rho) Ophiuchi}}
{{Starbox begin
| name=70 Ophiuchi
}}
{{Starbox image
|image={{Location mark
|image=Ophiuchus_constellation_map.svg
|alt=
|float=center
|width=280
|label=
|position=right
|mark=Red circle.svg
|mark_width=11
|x=254
|y=329
}}
|alt=70 Ophiuchi is located in the constellation Ophiuchus
|caption=Location of 70 Ophiuchi in the constellation [[Ophiuchus]]
}}
{{Starbox observe 3s
| epoch = J2000
| equinox = <!--Equinox of coordinates (defaults to epoch)-->
| constell = [[Ophiuchus]]
| component1 = 70 Ophiuchi
| ra1 = {{RA|18|05|27.285}}<ref name=aaa474_2_653/>
| dec1 = {{DEC|+02|29|00.36}}<ref name=aaa474_2_653/>
| appmag_v1 = 4.00 - 4.03<ref name=vsx/>
| component2 = A
| ra2 = {{RA|18|05|27.248}}<ref name=GaiaDR3a/>
| dec2 = {{DEC|+02|30|00.53}}<ref name=GaiaDR3a/>
| appmag_v2 = 4.13<ref name=tycho/>
| component3 = B
| ra3 = {{RA|18|05|27.463}}<ref name=GaiaDR3b/>
| dec3 = {{DEC|+02|29|56.21}}<ref name=GaiaDR3b/>
| appmag_v3 = 6.07<ref name=tycho/>
}}
{{Starbox character
| class=K0V + K4V<ref name=mk/>
| appmag_1_passband = B
| appmag_1 = 4.97/7.26<ref name=tycho/>
| appmag_3_passband = R
| appmag_3 = 3.6/5.6<ref name=tycho/>
| b-v= +0.82/+1.15<ref name=Piccotti2020/>
| u-b=+0.69<ref name=ubv/>
| variable= [[BY Draconis variable|BY Dra]]<ref name=gcvs/> or [[RS Canum Venaticorum variable|RS CVn]]<ref name=vsx/>
}}
{{Starbox astrometry
| component1             = 70 Oph A
| radial_v               = {{val|-5.73|0.18}}<ref name=GaiaDR3a/>
| prop_mo_ra             = {{val|206.525}}
| prop_mo_dec            = {{val|-1107.492|fmt=none}}
| pm_footnote            = <ref name=GaiaDR3a/>
| parallax               = 195.5674
| p_error                = 0.1964
| parallax_footnote      = <ref name=GaiaDR3a/>
| absmag_v               = +5.627<ref name=Piccotti2020/>
| component2             = 70 Oph B
| radial_v2              = {{val|-9.47|0.22}}<ref name=GaiaDR3b/>
| prop_mo_ra2            = {{val|333.292}}
| prop_mo_dec2           = {{val|-1068.354|fmt=none}}
| pm_footnote2           = <ref name=GaiaDR3b/>
| parallax2              = 195.2166
| p_error2               = 0.1012
| parallax_footnote2     = <ref name=dr2/>
| absmag_v2              = +7.427<ref name=Piccotti2020/>
}}
{{Starbox visbin
| reference              = <ref name=Eggenberger2008/>
| period                 = {{val|88.435|0.017}}
| axis_unitless          = {{val|4.526|0.007|ul="}}<ref name=Eggenberger2008/><br>({{val|23.6|0.5|ul=AU}}<ref name=Piccotti2020/>)
| eccentricity           = {{val|0.5005|0.0006}}
| inclination            = {{val|121.1|0.1}}
| periarg                = {{val|193.4|0.3}}
| periastron             = {{val|45809|14|fmt=commas}}
| node                   = {{val|121.7|0.2}} 
| k1                     = {{Val|3.51|0.04}}
| k2                     = {{val|4.25|0.05}}
}}
{{Starbox detail
| component1             = 70 Oph A
| mass                   = {{val|0.834|0.055}}<ref name=Piccotti2020/>
| radius                 = {{val|0.831|0.004}}<ref name=Boyajian/>
| metal_fe               = {{val|0.04|0.05}}<ref name=Eggenberger2008/>
| gravity                = 4.5<ref name="aaa259"/>
| rotation               = 19.7<ref name=aaa521_A12/> days
| luminosity_bolometric  = {{val|0.51|0.01}}<ref name=Piccotti2020/>
| habitable_inner        = 0.623<ref name=Boyajian/> AU
| habitable_outer        = 1.242<ref name=Boyajian/> AU
| temperature            = 5,282<ref name=Piccotti2020/>
| age_gyr                = {{Val|6.2|1.0}}<ref name=Eggenberger2008/>
| component2             = 70 Oph B
| mass2                  = {{val|0.782|0.064}}<ref name=Piccotti2020/>
| radius2                = {{val|0.670|0.009}}<ref name=Boyajian/>
| habitable_inner2       = 0.359<ref name=Boyajian/> AU
| habitable_outer2       = 0.712<ref name=Boyajian/> AU
| luminosity_bolometric2 = {{val|0.15|0.02}}<ref name=Eggenberger2008/>
| temperature2           = 4,623<ref name=Piccotti2020/>
| metal2_fe              = {{val|0.04|0.05}}<ref name=Eggenberger2008/>
| age_gyr2               = {{Val|6.2|1.0}}<ref name=Eggenberger2008/>
}}
{{Starbox catalog
| names = {{odlist | B=p Oph | F=70 Oph | V=V2391 Oph | BD=+02 3482 | GJ=702 | HD=165341 | HIP=88601 | HR=6752 | PLX=4137 | SAO=123107}}
| component1 = 70 Oph A
| names1 = {{odlist | LHS=458}}
| component2 = 70 Oph B
| names2 = {{odlist | LHS=459}}
}}
{{Starbox reference
| Simbad = V2391+Oph|sn=The system
| Simbad2 = TYC+434-5213-1|sn2=A
| Simbad3 = TYC+434-5212-1|sn3=B
| NSTED = HD-165341
| ARICNS = 01463
}}
{{Starbox end}}

'''70 Ophiuchi''' ('''p Ophiuchi''')<ref name="Gore1888"/> is a [[binary star|binary]] [[star system]] located 16.7 [[light-year]]s away from the [[Earth]].  It is in the [[constellation]] [[Ophiuchus]]. At [[apparent magnitude|magnitude 4]] it appears as a dim star visible to the unaided eye away from city lights.

==History==
In [[Ptolemy]]'s 2nd-century [[Almagest]] star catalogue this star system is listed as a 4th magnitude star, the ''28th'' (or ''4th outside the constellation figure'') in ''Ophiuchus''. It is star ''No. 261'' in this catalogue.<ref name=vizier/>

This star system was first catalogued as a binary star by [[William Herschel]] in the late 18th century in his study of binary stars. Herschel proved that this system is a gravitationally bound [[Binary star|binary]] system where the two stars orbit around a common [[center of mass]]. This was an important contribution to the proof that [[Newton's law of universal gravitation]] applied to objects beyond the [[Solar System]]. 

This star was once considered part of the obsolete constellation [[Taurus Poniatovii]], but after the [[International Astronomical Union]] officially recognized constellations, it was placed in Ophiuchus.<ref name=ridpath/>

==Variability==
[[File:V2391OphLightCurve.png|thumb|left|A [[light curve]] for V2391 Ophiuchi, plotted from ''[[Hipparcos]]'' data<ref name="CDS"/>]]
70 Ophiuchi is a variable star with a magnitude range for the two stars combined of 4.00 to 4.03.<ref name=vsx/>  The type of variability is uncertain and it is not clear which of the two components causes the variations.  It has been suspected of being either a [[BY Draconis variable]]<ref name=gcvs/> or an [[RS Canum Venaticorum variable]], and a period of 1.92396 days has been measured.<ref name=vsx/>

==Binary star==
The primary star is a yellow-orange [[main sequence]] dwarf of [[spectral type]] K0, while the secondary is an orange dwarf of [[spectral type]] K4.<ref name=mk/>  The two stars orbit each other at an average distance of 23.2 [[Astronomical unit|AU]]. But since the orbit is highly elliptical (at ''e''=0.499), the separation between the two varies from 11.4 to 34.8 AU,<ref name=solstation/> with one orbit taking 88.38 years to complete.<ref name=pourbaix/>

==Claims of a planetary system==
In 1855, [[William Stephen Jacob]] of the [[Madras Observatory]] claimed that the orbit of the binary showed an anomaly, and it was  "highly probable" that there was a "planetary body in connection with this system".<ref name=Jacob/> This is the first known attempt to use [[astrometry|astrometric]] methods to detect an [[exoplanet]], although [[Friedrich Bessel]] had applied similar methods 10 years earlier to deduce the existence of [[Sirius#Discovery of Sirius B|Sirius B]].<ref name="Kipping"/>

[[Thomas Jefferson Jackson See|T. J. J. See]] made a stronger claim for the existence of a dark companion in this system in 1899,<ref name="See"/> but [[Forest Ray Moulton]] soon published a paper proving that a three-body system with the specified orbital parameters would be highly unstable.<ref name=JHA/> The claims by Jacob and See have both been shown to be erroneous.<ref name="heintz1988"/>

Discovery of a "third dark companion" was announced by [[Louis Berman]] in 1932. This "dark body" around 70 Oph A was thought to have an 18-year period and a mass of 0.1 to 0.2 the [[Sun]]'s mass.<ref name=LOB/> A claim of a planetary system was again made, this time by [[Dirk Reuyl]] and [[Erik Holberg]] in 1943. The companion was estimated to have a mass 0.008 to 0.012 that of the [[Sun]] and a 17-year period.<ref name=OETCS70O/> This caused quite a sensation at the time but later observations have gradually discredited this claim.<ref name="heintz1988"/><ref name=SNT5P/><ref name=POMBS70O/>

The negative results of past studies does not completely rule out the possibility of planets. In 2006 a [[McDonald Observatory]] team set limits to the presence of one or more planets around 70 Ophiuchi with masses between 0.46 and 12.8 [[Jupiter masses]] and average separations spanning between 0.05 and 5.2 [[Astronomical Units|AU]].<ref name=search/>

==See also==
* [[61 Cygni]]
* [[Barnard's Star]]
* [[List of nearest stars]]
* [[List of nearest stars by spectral type#List of nearest K-type stars|List of nearest K-type stars]]

==References==
{{Reflist|refs=

<ref name=GaiaDR3a>{{Cite Gaia DR3|4468557611984384512}}</ref>

<ref name=GaiaDR3b>{{Cite Gaia DR3|4468557611977674496}}</ref>

<ref name=ridpath>{{cite web |url=http://www.ianridpath.com/startales/poniatowski.html |title=Taurus Poniatovii |author=Ian Ridpath |website=Star Tales |access-date=2023-11-01 }}</ref>

<ref name=Boyajian>{{Cite journal |last1=Boyajian |first1=Tabetha S. |last2=von Braun |first2=Kaspar |last3=van Belle |first3=Gerard |last4=McAlister |first4=Harold A. |last5=Brummelaar |first5=Theo A. ten |last6=Kane |first6=Stephen R. |last7=Muirhead |first7=Phil |last8=Jones |first8=Jeremy |last9=White |first9=Russel |last10=Schaefer |first10=Gail |last11=Ciardi |first11=David |last12=Henry |first12=Todd |last13=López-Morales |first13=Mercedes |last14=Ridgway |first14=Stephen |last15=Gies |first15=Douglas |date=2012-10-01 |title=Stellar Diameters and Temperatures II. Main Sequence K & M Stars |arxiv=1208.2431 |journal=The Astrophysical Journal |volume=757 |issue=2 |pages=112 |doi=10.1088/0004-637X/757/2/112 |bibcode=2012ApJ...757..112B |issn=0004-637X}}</ref>

<ref name=search>{{cite journal| title=Detection Limits from the McDonald Observatory Planet Search Program | date= 7 April 2006| author=Wittenmyer | journal=[[The Astronomical Journal]]| volume= 132| issue= 1| pages= 177–188| doi= 10.1086/504942| last2=Endl| first2=Michael| last3=Cochran| first3=William D.| last4=Hatzes| first4=Artie P.| last5=Walker| first5=G. A. H.| last6=Yang| first6=S. L. S.| last7=Paulson| first7=Diane B. | bibcode=2006AJ....132..177W|arxiv = astro-ph/0604171 | s2cid= 16755455}}</ref>

<ref name=POMBS70O>{{cite journal
| title=Parallax, orbit, and mass of the binary star 70 Ophiuchi
| author=Worth, M.D.
| journal=Astrophysical Journal
| volume=193
| pages=647–650
| date=November 1974 
| doi=10.1086/153202
| bibcode=1974ApJ...193..647W 
| doi-access=free
}}</ref>

<ref name=Eggenberger2008>{{Cite journal |last1=Eggenberger |first1=P. |last2=Miglio |first2=A. |last3=Carrier |first3=F. |last4=Fernandes |first4=J. |last5=Santos |first5=N. C. |date=2008-05-01 |title=Analysis of 70 Ophiuchi AB including seismic constraints |journal=Astronomy & Astrophysics |language=en |volume=482 |issue=2 |pages=631–638 |doi=10.1051/0004-6361:20078624 |issn=0004-6361|arxiv=0802.3576 |bibcode=2008A&A...482..631E }}</ref>

<ref name=OETCS70O>{{cite journal
| title= On the Existence of a Third Component in the System 70 Ophiuchi
| author=Reuyl, Dirk
| author2=Holmberg, Erik
| journal=The Astrophysical Journal
| volume=97 | pages=41–46 |date=January 1943 | doi=10.1086/144489
| bibcode=1943ApJ....97...41R }}</ref>

<ref name="SNT5P">{{cite journal
| title=Stars Nearer than Five Parsecs
| author=van de Kamp, Peter
| journal=Publications of the Astronomical Society of the Pacific
| volume=57
| number=334
| pages=34–41 (38*)
| date=February 1945 
| doi=10.1086/125679
| bibcode=1945PASP...57...34V 
| doi-access=free
}}</ref>

<ref name=LOB>{{cite journal
| title= 70 Ophiuchi as a Triple System
| author=Berman, Louis
| journal=Lick Observatory Bulletin
| number=443 | pages=24–30 |date=1932 | volume=16
| doi= 10.5479/ADS/bib/1932LicOB.16.24B
| bibcode= 1932LicOB..16...24B | doi-access=free}}</ref>

<ref name="heintz1988">{{cite journal |last=Heintz |first=W.D. |date=June 1988 |title=The Binary Star 70 Ophiuchi Revisited |journal=Journal of the Royal Astronomical Society of Canada |volume=82 |issue=3 |page=140 |bibcode=1988JRASC..82..140H }}</ref>

<ref name=JHA>{{cite journal |journal=Journal for the History of Astronomy |title=A Career of controversy: the anomaly OF T. J. J. See |last=Sherrill |first=Thomas J. |date=1999 |volume=30 |doi=10.1177/002182869903000102 | pages=25–50|bibcode=1999JHA....30...25S|s2cid=117727302}}</ref>

<ref name="See">{{cite journal |last=See |first=Thomas Jefferson Jackson |author-link=Thomas Jefferson Jackson See |date=1896 |title=Researches on the Orbit of F.70 Ophiuchi, and on a Periodic Perturbation in the Motion of the System Arising from the Action of an Unseen Body |journal=The Astronomical Journal |volume=16 |page=17 |doi=10.1086/102368 |bibcode=1896AJ.....16...17S}}</ref>

<ref name="Kipping">{{cite web | url=https://www.youtube.com/watch?v=2hNWCI-9n8Q | title=The First Exoplanet Claim: Captain William S Jacob| website=[[YouTube]]| date=2 December 2016}}</ref>

<ref name=Jacob>{{cite journal |last=Jacob |first=W.S. |date=1855 |title=On Certain Anomalies presented by the Binary Star 70 Ophiuchi |journal=[[Monthly Notices of the Royal Astronomical Society]] |volume=15 |issue=9 |pages=228–230 |url=https://books.google.com/books?id=pQsAAAAAMAAJ&q=editions:0B0EaWqbmirpeTa2sds |bibcode = 1855MNRAS..15..228J | doi = 10.1093/mnras/15.9.228|doi-access=free }}</ref>

<ref name=solstation>[http://www.solstation.com/stars/70ophiu2.htm Solstation article giving details of orbital mechanics of the system]</ref>

<ref name=vizier>{{cite web|url=https://vizier.cfa.harvard.edu/viz-bin/VizieR-5?-ref=VIZ62270d2f2c9e&-out.add=.&-source=J/A%2bA/544/A31/ptolema&recno=261 |title=Star Catalogue of Ptolemaios |publisher=Vizier.cfa.harvard.edu |date=2016-01-16 |accessdate=2022-03-27}}</ref>

<ref name="CDS">{{cite web
 | url=https://cdsarc.cds.unistra.fr/viz-bin/ftp-index?/ftp/cats/more/HIP/cdroms/cats
 | website=Centre de Données astronomiques de Strasbourg | title=/ftp/cats/more/HIP/cdroms/cats
 | publisher=Strasbourg astronomical Data Center | access-date=15 October 2022}}</ref>

<ref name=Piccotti2020>{{Cite journal |last1=Piccotti |first1=Luca |last2=Docobo |first2=José Ángel |last3=Carini |first3=Roberta |last4=Tamazian |first4=Vakhtang S. |last5=Brocato |first5=Enzo |last6=Andrade |first6=Manuel |last7=Campo |first7=Pedro P. |date=2020-02-01 |title=A study of the physical properties of SB2s with both the visual and spectroscopic orbits |journal=Monthly Notices of the Royal Astronomical Society |volume=492 |issue=2 |pages=2709–2721 |doi=10.1093/mnras/stz3616 |doi-access=free |issn=0035-8711 |bibcode=2020MNRAS.492.2709P }} [https://vizier.cds.unistra.fr/viz-bin/VizieR?-source=J/MNRAS/492/2709&HD=165341 70 Ophiuchi's database entry] at [[VizieR]].</ref>

<ref name=aaa474_2_653>{{cite journal | 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 }}</ref>

<ref name="aaa259">{{cite journal | last1=Morell | first1=O. | last2=Kallander | first2=D. | last3=Butcher | first3=H. R. | title=The age of the Galaxy from thorium in G dwarfs, a re-analysis | journal=Astronomy and Astrophysics | date=1999 | volume=259 | issue=2 | pages=543–548 | bibcode=1992A&A...259..543M }}</ref>

<ref name=aaa521_A12>{{cite journal | display-authors=1 | last1=Maldonado | first1=J. | last2=Martínez-Arnáiz | first2=R. M. | last3=Eiroa | first3=C. | last4=Montes | first4=D. | last5=Montesinos | first5=B. | title=A spectroscopy study of nearby late-type stars, possible members of stellar kinematic groups | journal=Astronomy and Astrophysics | volume=521 | page=A12 |date=October 2010 | doi=10.1051/0004-6361/201014948 | bibcode=2010A&A...521A..12M |arxiv = 1007.1132 | s2cid=119209183 }}</ref>

<ref name=gcvs>{{cite web
| url=http://www.sai.msu.su/groups/cluster/gcvs/cgi-bin/search.cgi?search=V2391+Oph
| work=[[General Catalog of Variable Stars]]
| publisher=[[Sternberg Astronomical Institute]], [[Moscow]], [[Russia]]
| title=GCVS Query= V2391 Oph
| access-date=2018-03-08
}}</ref>

<ref name=vsx>{{cite web
| url=https://www.aavso.org/vsx/index.php?view=detail.top&oid=22877
| work=International Variable Star Index
| publisher=[[AAVSO]]
| title=V2391 Oph
| access-date=2018-10-07
}}</ref>

<ref name=tycho>{{cite journal|bibcode=2002A&A...384..180F|title=The Tycho double star catalogue|journal=Astronomy and Astrophysics|volume=384|pages=180–189|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.|year=2002|doi=10.1051/0004-6361:20011822|doi-access=free}}</ref>

<ref name=dr2>{{cite DR2|4468557611977674496}}</ref>

<ref name=mk>{{cite journal|bibcode=1967AJ.....72.1334C|title=Spectral classification and photometry of high proper motion stars|journal=The Astronomical Journal|volume=72|page=1334|last1=Cowley|first1=A. P.|last2=Hiltner|first2=W. A.|last3=Witt|first3=A. N.|year=1967|doi=10.1086/110413|doi-access=free}}</ref>

<ref name=ubv>{{cite journal|bibcode=2002yCat.2237....0D|title=VizieR Online Data Catalog: Catalogue of Stellar Photometry in Johnson's 11-color system|journal=VizieR On-line Data Catalog|last1=Ducati|first1=J. R.|year=2002|volume=2237 }}</ref>

<ref name=pourbaix>{{cite journal|bibcode=2000A&AS..145..215P|doi=10.1051/aas:2000237|title=Resolved double-lined spectroscopic binaries: A neglected source of hypothesis-free parallaxes and stellar masses|journal=Astronomy and Astrophysics Supplement Series|volume=145|issue=2|pages=215–222|year=2000|last1=Pourbaix|first1=D.|doi-access=free}}</ref>

<ref name="Gore1888">{{cite journal |last1=Gore |first1=J. G. |date=March 1888 |title=On the Orbit of 70 (p) Ophiuchi |journal=[[Monthly Notices of the Royal Astronomical Society]] |volume=48 |issue= |page=257 |doi=10.1093/mnras/48.5.257 |doi-access=free |bibcode=1888MNRAS..48..257G}}</ref>

}}

==External links==
* {{cite web
| title=70 Ophiuchi
| work=SolStation
| url=http://www.solstation.com/stars/70ophiu2.htm
| access-date=October 24, 2005 }}
{{Sky|18|05|27.3|+|02|30|00|16.68}}
{{Nearest star systems|3}}
{{Stars of Ophiuchus}}

{{DEFAULTSORT:70 Ophiuchi}}
[[Category:Binary stars]]
[[Category:Flamsteed objects|Ophiuchi, 70]]
[[Category:Ophiuchus]]
[[Category:K-type main-sequence stars]]
[[Category:Solar analogs|Ophiuchi, 70]]
[[Category:Gliese and GJ objects|0702]]
[[Category:Objects with variable star designations|Ophiuchi, V2391]]
[[Category:Henry Draper Catalogue objects|165341]]
[[Category:Hipparcos objects|088601]]
[[Category:Bright Star Catalogue objects|6752]]
[[Category:Bayer objects|Ophiuchi, p]]
[[Category:Durchmusterung objects|BD+02 3482]]
[[Category:Hypothetical planetary systems]]