Xi Boötis

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Xi Boötis A/B
Diagram showing star positions and boundaries of the Boötes constellation and its surroundings
Diagram showing star positions and boundaries of the Boötes constellation and its surroundings
Location of ξ Boötis (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Boötes
Right ascension  14h 51m 23.37993s[1]
Declination +19° 06′ 01.6994″[1]
Apparent magnitude (V) 4.70/6.97
Spectral type G8 Ve + K4 Ve
U−B color index 0.24/1.15
B−V color index 0.73/1.15
R−I color index 0.43 / 0.28
Variable type BY Draconis/None
flare star
Radial velocity (Rv)+3.0[2] km/s
Proper motion (μ) RA: 154.98[1] mas/yr
Dec.: -66.43[1] mas/yr
Parallax (π)148.98 ± 0.48[1] mas
Distance21.89 ± 0.07 ly
(6.71 ± 0.02 pc)
Absolute magnitude (MV)5.54±0.007[3]
CompanionXi Boötis B
Period (P)151.505 ± 0.170 yr
Semi-major axis (a)4.9044 ± 0.0027
Eccentricity (e)0.5117 ± 0.0006
Inclination (i)140.037 ± 0.095°
Longitude of the node (Ω)168.100 ± 0.164°
Periastron epoch (T)1909.361 ± 0.024
Argument of periastron (ω)
23.917 ± 0.214°
ξ Boo A
Mass0.90 ± 0.04[5] M
Radius0.83[6] R
Luminosity (visual, LV)0.6041 ± 0.0040[7] L
Temperature5551 ± 20[5] K
Metallicity [Fe/H]–0.21 ± 0.08[5] dex
Age200[8] Myr
ξ Boo B
Mass0.66 ± 0.07[5] M
Radius0.61[6] R
Luminosity (visual, LV)0.061 L
Temperature4350 ± 150[5] K
Other designations
37 Boötis, BD +19°2870, GCTP 3360.00, Gl 566, HD 131156, HIP 72659, HR 5544, SAO 101250.
Database references

Xi Boötis (ξ Boo, ξ Boötis) is a binary star[5] system 22 light years away from Earth. It is the nearest visible star in the constellation Boötes; the brighter, primary component of the pair has a visual magnitude of 4.70, making it visible to the naked eye.


The primary star in this system is a BY Draconis variable with an apparent magnitude that varies from +4.52 to +4.67 with a period just over 10 days long, and is classified as a G-type main sequence star. It has 90% of the mass and 83% of the radius of the Sun, but shines with just 60% the Sun's luminosity; the secondary component is a K-type star, with just 66% of the Sun's mass and 61% of the Sun's radius.

The pair follow a wide, highly elliptical orbit around their common barycenter, completing an orbit every 151.5 years. Radial velocities taken of the primary as part of an extrasolar planet search show a linear trend in the velocities which is likely due to the secondary star;[9] the pair can be resolved even through smaller telescopes. The binary system contains some of the closest young solar-type stars to the Sun, with a system age of about 200 million years old.[8]

The primary star (A) has been identified as a candidate for possessing a Kuiper-like belt,[10] based on infrared observations; the estimated minimum mass of this dust disk is 2.4 times the mass of the Earth's Moon. (Compare to the value of 8.2 lunar masses for the Kuiper belt.)[11]

A necessary condition for the existence of a planet in this system are stable zones where the object can remain in orbit for long intervals. For hypothetical planets in a circular orbit around the individual members of this star system, this maximum orbital radius is computed to be 3.8 AU for the primary and 3.5 AU for the secondary. A planet orbiting outside of both stars would need to be at least 108 AU distant.[12]


  1. ^ a b c d e van Leeuwen, Floor (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752v1, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357 Note: see VizieR catalogue I/311.
  2. ^ Evans, D. S. (June 20–24, 1966), "The Revision of the General Catalogue of Radial Velocities", in Batten, Alan Henry; Heard, John Frederick (eds.), Determination of Radial Velocities and their Applications, Proceedings from IAU Symposium no. 30, University of Toronto: International Astronomical Union, Bibcode:1967IAUS...30...57E
  3. ^ Park, Sunkyung; et al. (2013), "Wilson-Bappu Effect: Extended to Surface Gravity", The Astronomical Journal, 146 (4): 73, arXiv:1307.0592, Bibcode:2013AJ....146...73P, doi:10.1088/0004-6256/146/4/73.
  4. ^ Wielen, R. (November 1962), "Automatic orbit computation for visual binaries", Astronomical Journal, 67: 599–607, Bibcode:1962AJ.....67..599W, doi:10.1086/108791 The data is from Orbit #3; the solution used by the 6th Washington Double Star catalogue for WDS 14514+1906.
  5. ^ a b c d e f Fernandes, J.; et al. (October 1998), "Fundamental stellar parameters for nearby visual binary stars: eta Cas, XI Boo, 70 OPH and 85 Peg. Helium abundance, age and mixing length parameter for low mass stars", Astronomy and Astrophysics, 338: 455–464, Bibcode:1998A&A...338..455F
  6. ^ a b c d Wood, Brian E.; Linsky, Jeffrey L. (July 2010), "Resolving the ξ Boo Binary with Chandra, and Revealing the Spectral Type Dependence of the Coronal "FIP Effect"", The Astrophysical Journal, 717 (2): 1279–1290, arXiv:1005.3281, Bibcode:2010ApJ...717.1279W, doi:10.1088/0004-637X/717/2/1279
  7. ^ 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): 31, arXiv:1306.2974, Bibcode:2013ApJ...771...40B, doi:10.1088/0004-637X/771/1/40, 40. See Table 3.
  8. ^ a b 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
  9. ^ Howard, Andrew W.; Fulton, Benjamin J. (2016). "Limits on Planetary Companions from Doppler Surveys of Nearby Stars". Publications of the Astronomical Society of the Pacific. 128 (969). 114401. arXiv:1606.03134. Bibcode:2016PASP..128k4401H. doi:10.1088/1538-3873/128/969/114401.
  10. ^ Hinshaw, Gary (February 3, 1997), Science Requirements Document (PDF), NASA JPL, archived from the original (PDF) on 2006-05-29, retrieved 2006-08-10
  11. ^ Holmes, E. K.; et al. (2003), "A Survey of Nearby Main-Sequence Stars for Submillimeter Emission", The Astronomical Journal, 125 (6): 3334–3343, Bibcode:2003AJ....125.3334H, doi:10.1086/375202
  12. ^ Jaime, Luisa G.; et al. (December 2012), "Regions of dynamical stability for discs and planets in binary stars of the solar neighbourhood", Monthly Notices of the Royal Astronomical Society, 427 (4): 2723–2733, arXiv:1208.2051, Bibcode:2012MNRAS.427.2723J, doi:10.1111/j.1365-2966.2012.21839.x.

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