A star chart of the constellation of Boötes showing the position of Tau Boötis (circled)
Epoch J2000.0 Equinox J2000.0
|Right ascension||13h 47m 15.74s|
|Declination||+17° 27′ 24.9″|
|Apparent magnitude (V)||4.50|
|Spectral type||F6 IV|
|U−B color index||0.04|
|B−V color index||0.48|
|R−I color index||0.24|
|Variable type||Variable star|
|Radial velocity (Rv)||-15.6 km/s|
|Proper motion (μ)||RA: -479.53 ± 0.16 mas/yr
Dec.: 53.49 ± 0.13 mas/yr
|Parallax (π)||64.03 ± 0.19 mas|
|Distance||50.9 ± 0.2 ly
(15.62 ± 0.05 pc)
|Absolute magnitude (MV)||3.38|
|τ Boo A|
|Mass||1.3 M☉|
|Radius||1.331 ± 0,027 R☉|
|Surface gravity (log g)||4.30 cgs|
|Rotational velocity (v sin i)||±1.015.6 km/s|
|Age||1.6–2.3  Gyr|
|τ Boo B|
|Mass||0.4 M☉|
Bright Star Catalogue (5th rev. ed.)
Tau Boötis (τ Boo, τ Boötis) is an F-type main-sequence star approximately 51 light-years away in the constellation of Boötes. The system is also a binary star system, with the secondary star being a red dwarf. As of 1999, an extrasolar planet has been confirmed to be orbiting the primary star.
The system is a binary. The primary component is a yellow-white dwarf (spectral type F7 V) and secondary is a dim red dwarf (spectral type M2 V). The system is relatively nearby, distance being about 51 light years. The primary star should be easily visible to the unaided eye under dark skies.
The primary star, Tau Boötis A is a yellow-white dwarf. It is 20 percent more massive than the Sun and thus is somewhat brighter and hotter. It has a radius 1.9 times solar, and is probably about 1.3 billion years old. Since it is more massive than the Sun, its lifespan is shorter - less than 6 billion years. Tau Bootis is the first star apart from the sun to be observed changing the polarity of its magnetic field. It is also listed as a suspected variable star.
In 1996 a planet, designated as Tau Boötis b, was discovered orbiting the primary star. There are also some indications of another, more distant, planet orbiting the star. In an unusual case of role-reversal, it appears that Tau Boötis' rotation has been tidally locked to Tau Boötis b. The planet was discovered by a team of astronomers led by Geoff Marcy and R. Paul Butler.
(in order from star)
|b||6±0.28 MJ||0.0481 ± 0.028||3.312463 ± 0.000014||0.023 ± 0.015||44.5 ± 1.5°||—|
The planet and its host star was one of the planetary systems selected by the International Astronomical Union as part of their public process for giving proper names to exoplanets and their host star (where no proper name already exists). The process involved public nomination and voting for the new names, and the IAU announced the new names in mid-December 2015. However, the IAU annulled the vote for the system, as the winning names ("Shri Ram Matt" for the star and "Bhagavatidevi" for the planet) were judged not to conform with the IAU rules for naming exoplanets. The names garnered the majority of the votes cast for the system, and also making up a significant proportion of all votes cast as part of the contest.
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- Mallik, Sushma V. (December 1999), "Lithium abundance and mass", Astronomy and Astrophysics, 352: 495–507, Bibcode:1999A&A...352..495M
- Reiners, A. (January 2006), "Rotation- and temperature-dependence of stellar latitudinal differential rotation", Astronomy and Astrophysics, 446 (1): 267–277, arXiv: , Bibcode:2006A&A...446..267R, doi:10.1051/0004-6361:20053911.
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- Mamajek, Eric E.; Hillenbrand, Lynne A. (2008). "Improved Age Estimation for Solar-Type Dwarfs Using Activity-Rotation Diagnostics". The Astrophysical Journal. 687 (2): 1264–1293. arXiv: . Bibcode:2008ApJ...687.1264M. doi:10.1086/591785.
- Donati, J.-F.; et al. (2008). "Magnetic cycles of the planet-hosting star Tau Boötis". Monthly Notices of the Royal Astronomical Society. 385 (3): 1179–1185. arXiv: . Bibcode:2008MNRAS.385.1179D. doi:10.1111/j.1365-2966.2008.12946.x.
- Butler, R. Paul; et al. (1997). "Three New 51 Pegasi Type Planets". The Astrophysical Journal Letters. 474 (2): L115–L118. Bibcode:1997ApJ...474L.115B. doi:10.1086/310444.
- Walker, G. A. H.; et al. (2008). "MOST detects variability on tau Bootis possibly induced by its planetary companion". Astronomy and Astrophysics. 482 (2): 691–697. arXiv: . Bibcode:2008A&A...482..691W. doi:10.1051/0004-6361:20078952.
- Butler, R. P.; et al. (2006). "Catalog of Nearby Exoplanets". The Astrophysical Journal. 646 (1): 505–522. arXiv: . Bibcode:2006ApJ...646..505B. doi:10.1086/504701.
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- "The Process". NameExoWorlds. International Astronomical Union. 30 November 2015. Retrieved 8 January 2016.
- "The Statistics". NameExoWorlds. International Astronomical Union. n.d. Retrieved 8 January 2016.
- "Final Results of NameExoWorlds Public Vote Released". International Astronomical Union. 15 December 2015. Retrieved 8 January 2016.
- "VizieR: HR 5185". Centre de Données astronomiques de Strasbourg. Retrieved 2009-05-15.
- "VizieR: CCDM J13473+1727". Centre de Données astronomiques de Strasbourg. Retrieved 2009-05-15.
- "Aladin Previewer: Tau Boötis". Centre de Données astronomiques de Strasbourg. Retrieved 2009-05-15.
- Schirber, Michael (23 May 2005). "Role Reversal: Planet Controls a Star". SPACE.com. Retrieved 2008-06-25.
- "Notes for star Tau Boo". The Extrasolar Planets Encyclopaedia. Retrieved 2008-06-25.
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