# Rho Andromedae

Observation data Constellation Epoch J2000.0      Equinox J2000.0 Location of ρ Andromedae (circled) Andromeda 00h 21m 07.26951s[1] +37° 58′ 06.9804″[1] +5.19[2] F5 III[3] +0.039[2] +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 27 Andromedae, BD+37 45, FK5 1009, HD 1671, HIP 1686, HR 82, SAO 53828.[3]

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]

## Naming

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]

## References

1. van Leeuwen, F. (November 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.
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/0405198, 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:
\begin{align} 2\cdot R_* & = \frac{(48.5\cdot 0.626\cdot 10^{-3})\ \text{AU}}{0.0046491\ \text{AU}/R_{\bigodot}} \\ & \approx 6.5\cdot R_{\bigodot} \end{align}
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:0711.4194, Bibcode:2008ApJS..176..276V, doi:10.1086/526548.
7. 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. ^