Tau Boötis

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τ Boötis
File:Tau Bootis-starmap.png
Location of τ Boötis (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Boötes
Right ascension Template:RA[1]
Declination Template:DEC[1]
Apparent magnitude (V) 4.50[2] (Script error: No such module "val".)[3]
Characteristics
Evolutionary stage Main sequence
Spectral type F6V + M2[4]
B−V Template:Engvar 0.48[2]
Variable type Suspected[3]
Astrometry
Radial velocity (Rv)−16.03±0.15[5] km/s
Proper motion (μ) RA: Script error: No such module "val". mas/yr[1]
Dec.: Script error: No such module "val". mas/yr[1]
Parallax (π)64.0470±0.1093 mas[1]
DistanceTemplate:Rnd ± Template:Rnd ly
(Template:Rnd ± Template:Rnd pc)
Absolute magnitude (MV)3.38[6]
Orbit[4]
Primaryτ Boo A
Companionτ Boo B
Period (P)Script error: No such module "val". yr
Semi-major axis (a)Script error: No such module "val".″
Eccentricity (e)Script error: No such module "val".
Inclination (i)Script error: No such module "val".°
Longitude of the node (Ω)Script error: No such module "val".°
Argument of periastron (ω)
(secondary)		Script error: No such module "val".°
Details
τ Boo A
MassScript error: No such module "val".[4] Template:Solar mass
RadiusScript error: No such module "val".[4] Template:Solar radius
LuminosityScript error: No such module "val".[7] Template:Solar luminosity
Surface gravity (log g)Script error: No such module "val".[4] cgs
TemperatureScript error: No such module "val".[4] K
Metallicity [Fe/H]Script error: No such module "val".[4] dex
RotationScript error: No such module "val". days[4]
Rotational velocity (v sin i)Script error: No such module "val".[7] km/s
AgeScript error: No such module "val".[4] Gyr
τ Boo B
MassScript error: No such module "val".[4] Template:Solar mass
RadiusScript error: No such module "val".[4] Template:Solar radius
Surface gravity (log g)4.90[8] cgs
TemperatureScript error: No such module "val".[4] K
Metallicity [Fe/H]+0.21[8] dex
Rotational velocity (v sin i)5.0[8] km/s
Other designations
Template:Odlist[9]
Database references
SIMBADdata
A
B

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Tau Boötis is a wide binary star system in the northern constellation of Boötes. Its name is a Bayer designation that is Latinised from τ Boötis, and abbreviated Tau Boo or τ Boo. This system is visible to the naked eye at a point of light with a combined apparent visual magnitude of 4.50.[2] Based on parallax measurements,[1] It is located at a distance of approximately Script error: No such module "convert". from the Earth. This system is drifting closer to the Sun with a radial velocity of −16 km/s.[5]

The primary component is an ordinary F-type main-sequence star that is larger, brighter, and more massive than the Sun, while the secondary is a faint red dwarf. In 1999, an extrasolar planet was detected orbiting the primary star.

Stellar components

The primary component is a yellow-white F-type main-sequence star with a stellar classification of F6V. It is 35 percent more massive and 42 percent larger than the Sun. The star is radiating three[7] times the luminosity of the Sun from its photosphere at an effective temperature of 6,387 K.[4] It is about 1.3 billion years old, making it younger than the Sun.[4] Since it is more massive than the Sun, its lifespan is shorter—less than 6 billion years. This star is spinning with a projected rotational velocity of 14.3 km/s,[7] completing a rotation every three days.[4]

The primary is the first star apart from the Sun to be observed changing the polarity of its magnetic field.[10] It is listed as a suspected variable star. The magnetic activity cycle for this star shows a period of 122 days—much shorter than the solar cycle.[11]

The secondary companion is a dim, 11th magnitude red dwarf of spectral type M2.[4] It only about half the mass and radius of the Sun.[4] The stars orbit each other at a typical distance of about 220 AU (14 arcseconds) but come as close as about 28 AU during periapsis, giving its orbit a very high eccentricity of about 0.87. One orbit around the primary would take approximately 2,400 years to complete, although this period is poorly constrained.[4]

Planetary system

In 1996 the exoplanet Tau Boötis b was discovered orbiting the primary star by a team of astronomers led by R. Paul Butler.[12] It has six times the mass of Jupiter and is orbiting the star with a period of 3.3 days.[13] Tau Boötis and its planet appear to be tidally locked to each other.[14] In 2014, water vapor was discovered in the atmosphere of this hot Jupiter.[15]

There are indications of a second planet orbiting the star with a period of roughly 5,000 days; however, this could be due to an instrumental effect or a stellar magnetic activity cycle.[16] Because this is a highly eccentric binary star system, the maximum exoplanetary orbit around the primary that is dynamically stable for long periods has a semimajor axis of Script error: No such module "val"..[17]

Template:OrbitboxPlanet begin Template:OrbitboxPlanet

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Naming controversy

The planet and its host star was one of the planetary systems selected by the International Astronomical Union as part of NameExoWorlds, their public process for giving proper names to exoplanets and their host star (where no proper name already exists).[18][19] The process involved public nomination and voting for the new names, and the IAU announced the new names in mid-December 2015.[20]

However, the IAU annulled the vote for the system, as the winning names ("Shri Ram Matt" for the star and "Bhagavatidevi" for the planet)[19] were judged not to conform with the IAU rules for naming exoplanets due to the political activities of the namesake people.[21] The names garnered the majority of the votes cast for the system, and made up a significant proportion of all votes cast as part of the contest.[19]

See also

References

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  1. ↑ a b c d e Template:Cite Gaia DR3
  2. ↑ a b c Script error: No such module "Citation/CS1".
  3. ↑ a b Script error: No such module "Citation/CS1". Search for: NSV 6444.
  4. ↑ a b c d e f g h i j k l m n o p q r Script error: No such module "Citation/CS1".
  5. ↑ a b Script error: No such module "Citation/CS1".
  6. ↑ Script error: No such module "Citation/CS1".
  7. ↑ a b c d Script error: No such module "Citation/CS1".
  8. ↑ a b c Script error: No such module "Citation/CS1".
  9. ↑ Template:Cite simbad
  10. ↑ Script error: No such module "Citation/CS1".
  11. ↑ Script error: No such module "Citation/CS1".
  12. ↑ Script error: No such module "Citation/CS1".
  13. ↑ Script error: No such module "Citation/CS1".
  14. ↑ Script error: No such module "Citation/CS1".
  15. ↑ Script error: No such module "Citation/CS1".
  16. ↑ Script error: No such module "Citation/CS1".
  17. ↑ Script error: No such module "Citation/CS1".
  18. ↑ Script error: No such module "citation/CS1".
  19. ↑ a b c Script error: No such module "citation/CS1".
  20. ↑ Script error: No such module "citation/CS1".
  21. ↑ Script error: No such module "citation/CS1".

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External links

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Template:Sky

Template:Stars of Boötes

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