HD 166

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HD 166 or ADS 69 A[1]
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Andromeda
Right ascension 00h 06m 36.78482s[2]
Declination +29° 01′ 17.4038″[2]
Apparent magnitude (V) 6.09[3]
Spectral type G8V[4]
U−B color index +0.30[3]
B−V color index +0.755[3]
Variable type BY Dra[5]
Radial velocity (Rv) −6.59[6] km/s
Proper motion (μ) RA: 380.98 ± 0.57[2] mas/yr
Dec.: −178.68 ± 0.29[2] mas/yr
Parallax (π) 73.15 ± 0.56[2] mas
Distance 44.6 ± 0.3 ly
(13.7 ± 0.1 pc)
Absolute magnitude (MV) 5.41[7]
Mass 0.889[4] M
Radius 0.9172 ± 0.0090[4] R
Luminosity 0.6078 ± 0.0099[4] L
Temperature 5,327 ± 39[4] K
Metallicity [Fe/H] 0.08[4] dex
Rotation 6.23 ± 0.01 days[8]
Age 9.6[4] Gyr
Other designations
BD+28°4704, GC 95, GSC 01735-02532, GSC 01735-00927, Gliese (Gl) 5, HD 166, HIP 544, HR 8, SAO 73743, New Suspected Variable (NSV) 33.
Database references

HD 166 or V439 Andromedae (ADS 69 A) is a 6th magnitude star in the constellation Andromeda, approximately 45 light years away from Earth. It is a variable star of the BY Draconis type,[5] with a variation in brightness smaller than 0.2 magnitude. This is a G-type main sequence star like the Sun, yet cooler and dimmer, having a stellar classification of G8V and an effective temperature of 5,327K.[4] It appears within one degree of the star Alpha Andromedae.[9]

The star has a proper motion of 0.422 arcseconds per year (114.1° from north). It has an estimated visual luminosity of 61% of the Sun. It has a diameter that is about 90% the size of the Sun and has a radial velocity of −6.6 km/s. Age estimates range from as low as 200 million years old based on its chromospheric activity,[10] up to 9.6[4] billion years. X-ray emission has been detected from this star, with an estimated luminosity of 8.5×1028 erg s−1.[11]

An infrared excess has been detected around this star, most likely indicating the presence of a circumstellar disk at a radius of 7.5 AU. The temperature of this dust is 90 K.[12]


  1. ^ "HD 166". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved October 12, 2007. 
  2. ^ a b c d e van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653–664. Bibcode:2007A&A...474..653V. arXiv:0708.1752Freely accessible. doi:10.1051/0004-6361:20078357. Vizier catalog entry
  3. ^ a b c Mermilliod, J.-C. (1986), "Compilation of Eggen's UBV data, transformed to UBV (unpublished)", Catalogue of Eggen's UBV data. SIMBAD, Bibcode:1986EgUBV........0M 
  4. ^ a b c d e f g h i Boyajian, Tabetha S.; et al. (July 2013), "Stellar Diameters and Temperatures. III. Main-sequence A, F, G, and K Stars: Additional High-precision Measurements and Empirical Relations", The Astrophysical Journal, 771 (1): 40, Bibcode:2013ApJ...771...40B, arXiv:1306.2974Freely accessible, doi:10.1088/0004-637X/771/1/40. 
  5. ^ a b Kazarovets; et al. (2006-08-08). "The 78th Name-List of Variable Stars". The Information Bulletin on Variable Stars Number 5721. Konkoly Observatory. Retrieved 2010-03-01. 
  6. ^ Nidever, David L.; et al. (August 2002), "Radial Velocities for 889 Late-Type Stars", The Astrophysical Journal Supplement Series, 141 (2): 503–522, Bibcode:2002ApJS..141..503N, arXiv:astro-ph/0112477Freely accessible, doi:10.1086/340570. 
  7. ^ Holmberg, J.; et al. (July 2009), "The Geneva-Copenhagen survey of the solar neighbourhood. III. Improved distances, ages, and kinematics", Astronomy and Astrophysics, 501 (3): 941–947, Bibcode:2009A&A...501..941H, arXiv:0811.3982Freely accessible, doi:10.1051/0004-6361/200811191. 
  8. ^ Gaidos; et al. (2000). "Spectroscopy and Photometry of Nearby Young Solar Analogs". The Astronomical Journal. 120 (2): 1006–1013. Bibcode:2000AJ....120.1006G. doi:10.1086/301488. 
  9. ^ Autostar Suite Astronomer Edition. CD-ROM. Meade, April 2006.
  10. ^ Mamajek, Eric E.; Hillenbrand, Lynne A. (November 2008). "Improved Age Estimation for Solar-Type Dwarfs Using Activity-Rotation Diagnostics". The Astrophysical Journal. 687 (2): 1264–1293. Bibcode:2008ApJ...687.1264M. arXiv:0807.1686Freely accessible. doi:10.1086/591785. 
  11. ^ Micela, G.; Favata, F.; Sciortino, S. (October 1997), "HIPPARCOS distances of X-ray selected stars: implications on their nature as stellar population", Astronomy and Astrophysics, 326: 221–227, Bibcode:1997A&A...326..221M 
  12. ^ Eiroa, C.; et al. (July 2013). "DUst around NEarby Stars. The survey observational results". Astronomy & Astrophysics. 555: A11. Bibcode:2013A&A...555A..11E. arXiv:1305.0155Freely accessible. doi:10.1051/0004-6361/201321050. 

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