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) +6.03
Spectral type G0V
U−B color index 0.19
B−V color index 0.62
Variable type None
Radial velocity (Rv) –1.1 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) +3.42
Mass 1.25 M
Radius 2 ± 0.7 R
Luminosity 3.95 L
Surface gravity (log g) 3.49 cgs
Temperature 5767 K
Metallicity 0.15 (141%)
Age 5.27×109 years
Other designations
CD –49° 13988, GSC 09340-01818, GJ 9802, HR 8700, HD 216435, HIP 113044, SAO 231343
Database references

Tau1 Gruis1 Gru, τ1 Gruis), also catalogued as HD 216435 and HR 8700, is a yellow dwarf 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 yellow dwarf star of the possible spectral type of G0-3 V-IV. It is thought that the star has about 1.25 times more mass than the Sun, a probable large radius, and about 3.6 times more luminosity. Due to its unusual brightness, at least one source suspects that the star may be a highly evolved subgiant star.[2] 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.[2] 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[3]
(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]


External links[edit]

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