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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