Tau1 Gruis

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Tau1 Gruis
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Grus
Right ascension 22h 53m 37.932s[1]
Declination –48° 35′ 53.83″[1]
Apparent magnitude (V) +6.02[2]
Spectral type G0 V[3]
U−B color index 0.17[2]
B−V color index 0.62[2]
Variable type None
Radial velocity (Rv) –1.1[4] km/s
Proper motion (μ) RA: 217.04±0.37[1] mas/yr
Dec.: −81.76±0.29[1] mas/yr
Parallax (π) 30.66 ± 0.39[1] mas
Distance 106 ± 1 ly
(32.6 ± 0.4 pc)
Absolute magnitude (MV) +3.46[5]
Mass 1.28±0.04[6] M
Radius 1.71±0.04[6] R
Luminosity 3.39±0.02[6] L
Surface gravity (log g) 4.07±0.03[6] cgs
Temperature 5,996±56[6] K
Metallicity [Fe/H] 0.27±0.02[7] dex
Rotational velocity (v sin i) 5.13[8] km/s
Age 4.2±0.6[6] Gyr
Other designations
τ1 Gru, CD−49° 13988, GJ 9802, HD 216435, HIP 113044, HR 8700, SAO 231343, GSC 09340-01818
Database references

Tau1 Gruis, Latinized from τ1 Gruis, and catalogued as HD 216435 and HR 8700, is a yellow-hued star approximately 106 light-years away[1] in the constellation of Grus (the Crane). The star is visible to the naked eye for some people, placing it in the Bright Star Catalogue. In 2002, one extrasolar planet was confirmed to orbit the star.


Tau1 Gruis is a G-type main-sequence star of spectral type G0 V. It is estimated that the star has about 1.28 times the mass of the Sun, 1.71 times the Sun's radius, and about 3.6 times the luminosity. Due to its unusual brightness, at least one source suspects that the star may be a highly evolved subgiant star.[9] It is thought that Tau1 Gruis is about 1.4 times more enriched with elements heavier than hydrogen, making a high abundance of iron likely. The Ca-II H line of the star suggests that it is chromospherically inactive, making it significantly older than previously predicted.

Planetary system[edit]

On September 17, 2002, a team of astronomers led by Geoffrey Marcy announced the discovery of a giant planet around Tau1 Gruis.[9] The radial velocity measurements suggest that the star has a companion with at least 1.23 times the mass of Jupiter. The planet's orbit stays inside the system's habitable zone for most of its revolution around the star, though at apoapsis, the planet falls outside of this zone.[citation needed]

The Tau1 Gruis planetary system[10]
(in order from star)
Mass Semimajor axis
Orbital period
Eccentricity Inclination Radius
b >1.26 ± 0.13 MJ 2.56 ± 0.17 1311 ± 49 0.070 ± 0.078

See also[edit]


  1. ^ a b c d e f van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653–664. arXiv:0708.1752Freely accessible. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. Vizier catalog entry
  2. ^ a b c Corben, P. M.; et al. (1972), "U, B, V photometry of 500 southern stars", Monthly Notes of the Astronomical Society of South Africa, 31: 7–22, Bibcode:1972MNSSA..31....8C. 
  3. ^ Gray, R. O.; et al. (July 2006), "Contributions to the Nearby Stars (NStars) Project: spectroscopy of stars earlier than M0 within 40 pc-The Southern Sample", The Astronomical Journal, 132 (1): 161–170, arXiv:astro-ph/0603770Freely accessible, Bibcode:2006AJ....132..161G, doi:10.1086/504637. 
  4. ^ Nordström, B.; et al. (May 2014), "The Geneva-Copenhagen survey of the Solar neighbourhood. Ages, metallicities, and kinematic properties of ~14000 F and G dwarfs", Astronomy and Astrophysics, 418 (3): 989–1019, arXiv:astro-ph/0405198Freely accessible, Bibcode:2004A&A...418..989N, doi:10.1051/0004-6361:20035959. 
  5. ^ Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters, 38 (5): 331, arXiv:1108.4971Freely accessible, Bibcode:2012AstL...38..331A, doi:10.1134/S1063773712050015. 
  6. ^ a b c d e f Bonfanti, A.; et al. (2015). "Revising the ages of planet-hosting stars". Astronomy and Astrophysics. 575: A18. arXiv:1411.4302Freely accessible. Bibcode:2015A&A...575A..18B. doi:10.1051/0004-6361/201424951. 
  7. ^ Tsantaki, M.; et al. (July 2013), "Deriving precise parameters for cool solar-type stars. Optimizing the iron line list", Astronomy & Astrophysics, 555: A150, arXiv:1304.6639Freely accessible, Bibcode:2013A&A...555A.150T, doi:10.1051/0004-6361/201321103. 
  8. ^ Delgado Mena, E.; et al. (April 2015), "Li abundances in F stars: planets, rotation, and Galactic evolution", Astronomy & Astrophysics, 576: 24, arXiv:1412.4618Freely accessible, Bibcode:2015A&A...576A..69D, doi:10.1051/0004-6361/201425433, A69. 
  9. ^ a b Jones, R. Paul; et al. (2003). "An exoplanet in orbit around τ1 Gruis". Monthly Notices of the Royal Astronomical Society. 341 (3): 948–952. arXiv:astro-ph/0209302Freely accessible. Bibcode:2003MNRAS.341..948J. doi:10.1046/j.1365-8711.2003.06481.x. 
  10. ^ Butler, R. P.; et al. (2006). "Catalog of Nearby Exoplanets". The Astrophysical Journal. 646 (1): 505–522. arXiv:astro-ph/0607493Freely accessible. Bibcode:2006ApJ...646..505B. doi:10.1086/504701. 

External links[edit]

Coordinates: Sky map 22h 53m 37.9315s, −48° 35′ 53.828″