Epoch J2000.0 Equinox J2000.0
|Right ascension||22h 53m 37.932s|
|Declination||–48° 35′ 53.83″|
|Apparent magnitude (V)||+6.03|
|U−B color index||0.19|
|B−V color index||0.62|
|Radial velocity (Rv)||–1.1 km/s|
|Proper motion (μ)||RA: 217.04 ± 0.37 mas/yr
Dec.: -81.76 ± 0.29 mas/yr
|Parallax (π)||30.66 ± 0.39 mas|
|Distance||106 ± 1 ly
(32.6 ± 0.4 pc)
|Absolute magnitude (MV)||+3.42|
|Radius||2 ± 0.7 R☉|
|Surface gravity (log g)||3.49 cgs|
Tau1 Gruis (τ1 Gru, τ1 Gruis), also catalogued as HD 216435 and HR 8700, is a yellow dwarf star approximately 106 light-years away 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. 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.
On September 17, 2002, a team of astronomers led by Geoffrey Marcy announced the discovery of a giant planet around Tau1 Gruis. 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.
(in order from star)
|b||>1.26 ± 0.13 MJ||2.56 ± 0.17||1311 ± 49||0.070 ± 0.078||—||—|
- van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653–664. arXiv: . Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357.Vizier catalog entry
- 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: . Bibcode:2003MNRAS.341..948J. doi:10.1046/j.1365-8711.2003.06481.x.
- 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.
- "Notes for star HD 216435". The Extrasolar Planets Encyclopaedia. Retrieved 2008-06-22.
- "Tau1 Gruis". Solstation. Retrieved 2008-06-22.