Tau Geminorum

Tau Geminorum
Location of τ Geminorum (circled)
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Gemini
Right ascension 07h 11m 08.3703s[1]
Declination +30° 14′ 42.590″[1]
Apparent magnitude (V) +4.42[2]
Characteristics
Spectral type K2 III[3]
U−B color index +1.41[2]
B−V color index +1.261[3]
Astrometry
Radial velocity (Rv)+22.02±0.07[3] km/s
Proper motion (μ) RA: −30.725(167) mas/yr[1]
Dec.: −48.515(166) mas/yr[1]
Parallax (π)8.3261 ± 0.1591 mas[1]
Distance392 ± 7 ly
(120 ± 2 pc)
Absolute magnitude (MV)−0.56±0.05[3]
Details
Mass2.3±0.3[3] M☉
Radius30.27+1.08
−1.09[4] R☉
Luminosity364±14[4] L☉
Surface gravity (log g)1.96±0.08[3] cgs
Temperature4,583±70[4] K
Metallicity [Fe/H]0.14±0.10[3] dex
Rotational velocity (v sin i)5.8[5] km/s
Age1.22±0.76[3] Gyr
Other designations
τ Gem, 46 Gem, BD+30 1439, HD 54719, HIP 34693, HR 2697, SAO 59858
Database references
SIMBADdata

Tau Geminorum, Latinized from τ Geminorum, is a star in the northern zodiac constellation of Gemini. It has the apparent visual magnitude of +4.42,[2] making it visible to the naked eye under suitably good seeing conditions. This star is close enough to the Earth that its distance can be measured using the parallax technique, which yields a value of roughly 392 light-years (120 parsecs).[1]

Artist's illustration of the giant star Tau Geminorum (left) and its brown dwarf companion—the dark disk at right.

It is an evolved giant star of the spectral type K2 III. It has double[6] the mass of the Sun and has expanded to 30 times the Sun's radius. Tau Geminorum is radiating 364[4] times as much radiation as the Sun from its expanded outer atmosphere at an effective temperature of 4,583 K,[4] giving it the characteristic orange-hued glow of a K-type star. It appears to be rotating slowly with a projected rotational velocity of 5.8 km/s.[5]

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  2. ^ a b c Cite error: The named reference clpl4_99 was invoked but never defined (see the help page).
  3. ^ a b c d e f g h Cite error: The named reference Mitchell_et_al_2013 was invoked but never defined (see the help page).
  4. ^ a b c d e Cite error: The named reference npoi was invoked but never defined (see the help page).
  5. ^ a b Cite error: The named reference aj135_1_209 was invoked but never defined (see the help page).
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