HD 218566

From Wikipedia, the free encyclopedia
Jump to: navigation, search
HD 218566
Observation data
Epoch J2000      Equinox J2000
Constellation Pisces
Right ascension 23h 09m 10.72771s[1]
Declination −02° 15′ 38.6775″[1]
Apparent magnitude (V) 8.628[2]
Spectral type K3 V[3]
B−V color index 1.014[3]
Proper motion (μ) RA: +632.56[1] mas/yr
Dec.: –97.02[1] mas/yr
Parallax (π) 35.02 ± 1.14[1] mas
Distance 93 ± 3 ly
(28.6 ± 0.9 pc)
Absolute magnitude (MV) 6.187[3]
Mass 0.81 ± 0.06[4] M
Radius 0.86 ± 0.08[2] R
Luminosity 0.353 ± 0.032[2] L
Surface gravity (log g) 4.48 ± 0.04[4] cgs
Temperature 4,849 ± 42[4] K
Metallicity [Fe/H] 0.38[3] dex
Rotational velocity (v sin i) 0.0[2] km/s
Age 8.5[2] to 11.5[4] Gyr
Other designations
BD-03 5577, HD 218566, HIP 114322, SAO 146533.

HD 218566 is a star in the equatorial zodiac constellation of Pisces. With an apparent visual magnitude of 8.6,[2] this ninth magnitude star can not be viewed with the naked eye. However, it can be readily seen even with a small telescope.[5]

HD 218566 is a smaller star than the Sun, with about 81%[4] of the Sun's mass and 86% of the radius of the Sun.[2] It is a K-type main sequence star with a stellar classification of K3 V[3] that is generating energy by the nuclear fusion of hydrogen at its core. HD 218556 is radiating around 35% of the luminosity of the Sun from its outer envelope at an effective temperature of 4,849 K.[4] This heat gives the star the characteristic orange-hued glow of a K-type star.[6]

Compared to the Sun, this star has an unusually high abundance of elements other than hydrogen and helium, what astronomers term the metallicity. Based upon the abundance of iron, the metallicity is 2.4 times as high as in the Sun.[2] It is much older than the Sun, with estimates of its age ranging from 8.5[2] to 11.5[4] billion years. It appears to have a negligible rate of spin as its projected rotational velocity is too small to measure.[2]

This star belongs to the thick disk population of the Milky Way. In the galactic coordinate system, it has space velocity components of [U, V, W] = [77, –61, –8] km s−1. HD 218556 is following an orbit through the galaxy with an eccentricity of 0.36 ± 0.01 that carries it as close as 14.3 kly (4.4 kpc) and as far as 30.3 kly (9.3 kpc) from the Galactic Center. The orbital tilt carries this star as much as 0.6 kly (0.18 kpc) from the galactic plane.[4]

Based upon high resolution measurements performed at the W. M. Keck Observatory, HD 218566 shows cyclical variations in radial velocity that suggest gravitational perturbation by orbiting companion. This candidate object is estimated to be orbiting the parent star with a period of 225.7 ± 0.4 days at an eccentricity of 0.3 ± 0.1. The semi-major axis for this Keplerian orbit is an estimated 0.6873 Astronomical Units. Because the inclination of the orbit remains unknown, the mass of this companion has not been determined. However, it can be constrained to have a mass of at least 21% the mass of Jupiter. There is no evidence of additional companions in the system.[2]


  1. ^ a b c d e 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 e f g h i j k Meschiari, Stefano; et al. (February 2011), "The Lick-Carnegie Survey: Four New Exoplanet Candidates", The Astrophysical Journal, 727 (2): 117, arXiv:1011.4068Freely accessible, Bibcode:2011ApJ...727..117M, doi:10.1088/0004-637X/727/2/117 
  3. ^ a b c d e Soubiran, C.; et al. (2008), "Vertical distribution of Galactic disk stars. IV. AMR and AVR from clump giants", Astronomy and Astrophysics, 480 (1): 91–101, arXiv:0712.1370Freely accessible, Bibcode:2008A&A...480...91S, doi:10.1051/0004-6361:20078788 
  4. ^ a b c d e f g h Trevisan, M.; et al. (November 2011), "Analysis of old very metal rich stars in the solar neighbourhood", Astronomy & Astrophysics, 535: A42, arXiv:1109.6304Freely accessible, Bibcode:2011A&A...535A..42T, doi:10.1051/0004-6361/201016056 . See table 13.
  5. ^ Sherrod, P. Clay; Koed, Thomas L. (2003), A Complete Manual of Amateur Astronomy: Tools and Techniques for Astronomical Observations, Astronomy Series, Courier Dover Publications, p. 9, ISBN 0-486-42820-6 
  6. ^ "The Colour of Stars", Australia Telescope, Outreach and Education, Commonwealth Scientific and Industrial Research Organisation, December 21, 2004, retrieved 2012-01-16