Rho Andromedae

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Rho Andromedae
Diagram showing star positions and boundaries of the Andromeda constellation and its surroundings
Cercle rouge 100%.svg

Location of ρ Andromedae (circled)
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Andromeda
Right ascension 00h 21m 07.26951s[1]
Declination +37° 58′ 06.9804″[1]
Apparent magnitude (V) +5.19[2]
Spectral type F5 III[3]
U−B color index +0.039[2]
B−V color index +0.424[2]
Radial velocity (Rv) +8.2[4] km/s
Proper motion (μ) RA: +58.93[1] mas/yr
Dec.: -38.56[1] mas/yr
Parallax (π) 20.60 ± 0.21[1] mas
Distance 158 ± 2 ly
(48.5 ± 0.5 pc)
Absolute magnitude (MV) +1.73[4]
Radius 3.3[5] R
Luminosity 20[6] L
Surface gravity (log g) 3.84[7] cgs
Temperature 6,471[7] K
Metallicity [Fe/H] –0.09[7] dex
Rotational velocity (v sin i) 44[7] km/s
Age 1.3[4] Gyr
Other designations
27 Andromedae, BD+37 45, FK5 1009, HD 1671, HIP 1686, HR 82, SAO 53828.[3]
Database references

Rho Andromedae (ρ And, ρ Andromedae) is the Bayer designation for a star in the northern constellation of Andromeda. It has an apparent visual magnitude of +5.19,[2] which, according to the Bortle Dark-Sky Scale, is bright enough to be seen with the naked eye from dark suburban skies. Based upon parallax measurements, this star is at a distance of approximately 158 light-years (48 parsecs) from Earth.[1]

The stellar classification of this star is F5 III,[3] indicating that it is in the giant stage of its stellar evolution. However, some sources list a classification of F5 IV,[3][6] suggesting that it may still be in the subgiant stage. The interferometry-measured angular diameter of this star is 0.626 mas,[6] which, at its estimated distance, equates to a physical radius of around 3.3 times the radius of the Sun.[5] The outer envelope is radiating around 20[6] times the luminosity of the Sun into space at an effective temperature of 6,471 K,[7] giving it the yellow-white hue of an F-type star.[8] It is about 1.3 billion years old.[4]

X-ray emissions were detected from this star during the EXOSAT mission.[9]


In Chinese, 天廄 (Tiān Jiù), meaning Celestial Stable, refers to an asterism consisting of ρ Andromedae, θ Andromedae and σ Andromedae. Consequently, ρ Andromedae itself is known as 天廄二 (Tiān Jiù èr, English: the Second Star of Celestial Stable.)[10]


  1. ^ a b c d e f van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752Freely accessible, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357. 
  2. ^ a b c d Breger, M. (March 1968), "UBV and narrow-band UVBY photometry of bright stars", Astronomical Journal, 73: 84–85, Bibcode:1968AJ.....73...84B, doi:10.1086/110602. 
  3. ^ a b c d "rho And -- Star", SIMBAD Astronomical Object Database, Centre de Données astronomiques de Strasbourg, retrieved 2012-06-24. 
  4. ^ a b c d Nordström, B.; et al. (May 2004), "The Geneva-Copenhagen survey of the Solar neighbourhood. Ages, metallicities, and kinematic properties of ˜14 000 F and G dwarfs", Astronomy and Astrophysics, 418: 989–1019, arXiv:astro-ph/0405198Freely accessible, Bibcode:2004A&A...418..989N, doi:10.1051/0004-6361:20035959. 
  5. ^ a b Lang, Kenneth R. (2006), Astrophysical formulae, Astronomy and astrophysics library, 1 (3rd ed.), Birkhäuser, ISBN 3-540-29692-1.  The radius (R*) is given by:
  6. ^ a b c d van Belle, G. T.; et al. (May 2008), "The Palomar Testbed Interferometer Calibrator Catalog", The Astrophysical Journal Supplement Series, 176 (1): 276–292, arXiv:0711.4194Freely accessible, Bibcode:2008ApJS..176..276V, doi:10.1086/526548. 
  7. ^ a b c d e Balachandran, Suchitra (May 1, 1990). "Lithium depletion and rotation in main-sequence stars". Astrophysical Journal, Part 1. 354: 310–332. Bibcode:1990ApJ...354..310B. doi:10.1086/168691. 
  8. ^ "The Colour of Stars", Australia Telescope, Outreach and Education, Commonwealth Scientific and Industrial Research Organisation, December 21, 2004, retrieved 2012-01-16. 
  9. ^ Gondoin, P.; Mangeney, A.; Praderie, F. (March 1987), "Solar-type giants - New X-ray detections from EXOSAT observations", Astronomy and Astrophysics, 174 (1-2): 187–196, Bibcode:1987A&A...174..187G. 
  10. ^ (Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 5 月 18 日

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