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 36.78s[2]
Declination +29° 01′ 17.4″[2]
Apparent magnitude (V) 6.13
Spectral type G8V[3]
U−B color index +0.33
B−V color index +0.75
Variable type BY Draconis variable [4]
Radial velocity (Rv) -8.2 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)
Mass 0.889[3] M
Radius 0.9172 ± 0.0090[3] R
Luminosity 0.6078 ± 0.0099[3] L
Temperature 5327 ± 39[3] K
Metallicity [Fe/H] 0.08[3] dex
Rotation 6.23 ± 0.01 days[5]
Age 9.6[3] Gyr
Other designations
HR 8, BD+28°4704, SAO 73743, HIP 544, GC 95, GSC 01735-02532, GSC 01735-00927, Gliese (Gl) 5, 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,[4] with a variation in brightness smaller than 0.2 magnitude. It is a dwarf star like our Sun, yet cooler and dimmer, having a stellar classification of spectral type G8V and a surface temperature of 5,327 kelvin.[3] It is within one degree of the star Alpha Andromedae.[6]

It is located at celestial (X,Y,Z) coordinates of 39.1, 1.13, 21.7 galactic (X,Y,Z) coordinates in ly: -14.1, 34.9, -24.1 and is found at right ascension and declination 0h6m36.75s, +29°1'17.6".

The star has a proper motion of 0.422 arcsecond per year (114.1° from north). It has an estimated visual luminosity of 61% of Sol. It has a diameter that is about 0.91 x Sol and has a radial velocity of -5.5 km/s. It is estimated to be about 200 million years old based on its chromospheric activity.[7] X-ray emission has been detected from this star, with an estimated luminosity of 8.5 × 1028 erg s−1.[8]

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.[9]

The habitable zone for an Earth-like planet would be about 0.77 AU from the star.


  1. ^ "Simbad Query Result". Simbad. 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. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. Vizier catalog entry
  3. ^ a b c d e f g h 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, arXiv:1306.2974, Bibcode:2013ApJ...771...40B, doi:10.1088/0004-637X/771/1/40. 
  4. ^ 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. 
  5. ^ 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. 
  6. ^ Autostar Suite Astronomer Edition. CD-ROM. Meade, April 2006.
  7. ^ 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. arXiv:0807.1686. Bibcode:2008ApJ...687.1264M. doi:10.1086/591785. 
  8. ^ 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 
  9. ^ Eiroa, C. et al. (July 2013). "DUst around NEarby Stars. The survey observational results". Astronomy & Astrophysics 555: A11. arXiv:1305.0155. Bibcode:2013A&A...555A..11E. doi:10.1051/0004-6361/201321050. 

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