12 Ophiuchi

{{Short description|Star in the constellation Ophiuchus}}

{{Starbox begin

| name=12 Ophiuchi

}}

{{Starbox observe

| epoch=J2000

| ra={{RA|16|36|21.44969}}

| dec={{DEC|-02|19|28.5130}}

| appmag_v=5.77

| constell=Ophiuchus

}}

{{Starbox character

| class=K1 V

| b-v=+.82

| u-b=+0.50

| variable=BY Draconis

}}

{{Starbox astrometry

| radial_v={{val|-13.11|0.12}}

| prop_mo_ra=+456.058

| prop_mo_dec=−309.224

| pm_footnote=

| parallax=101.0719

| p_error=0.0501

| parallax_footnote=

| absmag_v={{nowrap|5.57 ± 0.05}}

}}

{{Starbox detail

| mass=0.91

| radius={{val|0.84|0.03}}

| luminosity=0.39

| luminosity_bolometric=0.45

| gravity={{val|4.59|0.10}}

| temperature=5,300

| metal_fe={{val|+0.04|0.07}}

| metal=102% Sun

| rotation=21.3 days

| rotational_velocity={{val|2.4|1.0}}

| age_gyr=1.0–1.9

}}

{{Starbox catalog

| names={{odlist | F=12 Oph | V=V2133 Oph | BD=−01 3220, BD−02 4211 | FK5=1433 | GJ=631 | HD=149661 | HIP=81300 | HR=6171 | LHS=3224 | LTT=6632 | PLX=3773 | SAO=141269}}

}}

{{Starbox reference

| Simbad=HD+149661

| ARICNS=01317

}}

{{Starbox end}}

12 Ophiuchi is a variable star 32.3 light-years away in the constellation Ophiuchus. No companions have yet been detected in orbit around this star, and it remains uncertain whether or not it possesses a dust ring.{{cite journal | display-authors=6 | author=H. J. Habing | author2=P. Bouchet | author3=C. Dominik | author4=T. Encrenaz |author4-link=Thérèse Encrenaz| author5=A. Heske | author6=M. Jourdain de Muizon | author7=M. F. Kessler | author8=R. Laureijs| author9=K. Leech | author10=L. Metcalfe| author11=A. Salama | author12=R. Siebenmorgen| author13=N. Trams | author14=C. Waelkens| author15=L. B. F. M. Waters | title=First results from a photometric infrared survey for Vega-like disks around nearby main-sequence stars. | journal=Astronomy and Astrophysics | date=1996 | volume=315 | pages=L233–L236 | bibcode=1996A&A...315L.233H }}

This star is categorized as a BY Draconis variable, with variable star designation V2133. The variability is attributed to large-scale magnetic activity on the chromosphere (in the form of starspots) combined with a rotational period that moved the active regions into (and out of) the line of sight. This results in low amplitude variability of 12 Ophiuchi's luminosity. The star also appears to display rapid variation in luminosity, possibly due to changes in the starspots.{{cite journal | author=J. D. Dorren | author2=E. F. Guinan | author3= E. F. | title=Evidence for starspots on single solar-like stars | journal=Astronomical Journal | date=1982 | volume=87 | pages=1546–1557 | bibcode=1982AJ.....87.1546D | doi=10.1086/113245 }} Measurements of the long-term variability show two overlapping cycles of starspot activity (compared to the Sun's single, 11-year cycle.) The periods of these two cycles are 4.0 and 17.4 years.{{cite web|url=http://www.mtwilson.edu/hk/Cycles/ |title=H-K Project: Activity Cycles |publisher=Mount Wilson Observatory |accessdate=2006-12-04 |url-status=dead |archiveurl=https://web.archive.org/web/20070209092256/http://www.mtwilson.edu/hk/Cycles/ |archivedate=2007-02-09 }}

This star was among the top 100 target stars for NASA's canceled Terrestrial Planet Finder mission.

Its abundance of heavy elements (elements heavier than helium) is nearly identical to that of the Sun. The surface gravity is equal to $\backslash log(g)\; =\; 4.6$, which is somewhat higher than the Sun's. The space velocity is 30 km/s relative to the Solar System. The high rotation period and active chromosphere are indicative of a relatively young star.{{cite journal | author=H. J. Rocha-Pinto | author2=B. V. Castilho | author3=W. J. Maciel | title=Chromospherically young, kinematically old stars | journal=Astronomy & Astrophysics | date=2002 | volume=384 | issue=3 | pages=912–924 | url=http://www.aanda.org/index.php?option=com_base_ora&url=articles/aa/full/2002/12/aa1635/aa1635.right.html&access=standard&Itemid=81 | doi=10.1051/0004-6361:20011815 | bibcode=2002A&A...384..912R|arxiv = astro-ph/0112452 | s2cid=16982360 }}{{cite journal | author=G. F. Porto de Mello | author2=E. F. del Peloso | author3=L. Ghezzi | title=Astrobiologically interesting stars within 10 parsecs of the Sun | journal=Astrobiology | date=2006 | volume=6 | issue=2 | pages=308–331 | url=http://www.liebertonline.com/doi/abs/10.1089/ast.2006.6.308 | doi=10.1089/ast.2006.6.308 | pmid=16689649 | bibcode=2006AsBio...6..308P|arxiv = astro-ph/0511180 | s2cid=119459291 }}