Tau Draconis

Tau Draconis
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Draco
Right ascension 19h 15m 33.05868s[1]
Declination +73° 21′ 19.6769″[1]
Apparent magnitude (V) 4.45[2]
Characteristics
Spectral type K2 III:[3]
U−B color index +1.45[2]
B−V color index +1.25[2]
Astrometry
Radial velocity (Rv)−33.70[3] km/s
Proper motion (μ) RA: −115.29[1] mas/yr
Dec.: +103.23[1] mas/yr
Parallax (π)22.28 ± 0.50 mas[1]
Distance146 ± 3 ly
(45 ± 1 pc)
Absolute magnitude (MV)+1.19[4]
Details
Mass1.25[3] M☉
Luminosity48[3] L☉
Surface gravity (log g)2.00[5] cgs
Temperature4,413±77[3] K
Metallicity [Fe/H]0.17±0.06[6] dex
Rotational velocity (v sin i)8[7] km/s
Age6.48[3] Gyr
Other designations
τ Dra, 60 Dra, BD+73° 857, FK5 729, HD 181984, HIP 94648, HR 7352, SAO 9366[8]
Database references
SIMBADdata

Tau Draconis, Latinized from τ Draconis, is an astrometric binary[9] star system in the northern circumpolar constellation of Draco. The star is faintly visible to the naked eye, having an apparent visual magnitude of 4.45.[2] Based upon an annual parallax shift of 22.28 mas as measured from Earth,[1] it is located around 146 light years from the Sun. Its proper motion is propelling it across the sky at the rate of 0.176 arc seconds per year.[10]

This is a K-type giant star with a stellar classification of K2 III:,[3] where the semi-colon indicates some uncertainty about its spectral value. It is considered metal-rich[6] star and is past the first dredge-up phase of its post-main sequence evolution, although it shows under-abundances of carbon and oxygen in its spectrum.[5] The star has 1.25[3] times the mass of the Sun and is an estimated 6.48[3] billion years old. It is radiating 48[3] times the solar luminosity from its enlarged photosphere at an effective temperature of 4,413 K.[3]

  1. ^ a b c d e f Cite error: The named reference vanLeeuwen2007 was invoked but never defined (see the help page).
  2. ^ a b c d Cite error: The named reference Johnson1966 was invoked but never defined (see the help page).
  3. ^ a b c d e f g h i j k Cite error: The named reference Luck2015 was invoked but never defined (see the help page).
  4. ^ Cite error: The named reference Anderson2012 was invoked but never defined (see the help page).
  5. ^ a b Cite error: The named reference Mishenina1995 was invoked but never defined (see the help page).
  6. ^ a b Cite error: The named reference Taylor2002 was invoked but never defined (see the help page).
  7. ^ Cite error: The named reference Bernacca1970 was invoked but never defined (see the help page).
  8. ^ Cite error: The named reference SIMBAD was invoked but never defined (see the help page).
  9. ^ Cite error: The named reference Eggleton2008 was invoked but never defined (see the help page).
  10. ^ Cite error: The named reference Lepine2005 was invoked but never defined (see the help page).