Rho Boötis

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ρ Boötis
Observation data
Epoch J2000      Equinox J2000
Constellation Boötes
Right ascension 14h 31m 49.7899s
Declination +30° 22′ 17.174″
Apparent magnitude (V) 3.583
Spectral type K3 III
U−B color index 1.44
B−V color index 1.3
R−I color index 0.65
Radial velocity (Rv) –13.7 km/s
Proper motion (μ) RA: –100.44 mas/yr
Dec.: +120.22 mas/yr
Parallax (π) 21.92 ± 0.81 mas
Distance 149 ± 5 ly
(46 ± 2 pc)
Mass 1.0–1.4[1] M
Radius 21.57 ± 0.25[1] R
Luminosity 131.9 ± 6.8[1] L
Temperature 4,298 ± 56[1] K
Other designations
25 Boötis, BD+31° 2628, FK5 534, HD 127665, HIP 71053, HR 5429, SAO 64202.
Database references

Rho Boötis (ρ Boo, ρ Boötis) is a star in the northern constellation Boötes. Based upon parallax measurements, it is located at a distance of approximately 149 light-years (46 parsecs) from Earth.

This is an orange K-type giant with an apparent magnitude of +3.57. Since 1943, the spectrum of this star has served as one of the stable anchor points by which other stars are classified.[2] There is an optical companion, an eleventh magnitude star, located 42 arcseconds away.

In Chinese, 梗河 (Gěng Hé), meaning Celestial Lance, refers to an asterism consisting of ρ Boötis, ε Boötis and σ Boötis.[3] Consequently, ρ Boötis itself is known as 梗河三 (Gěng Hé sān, English: the Third Star of Celestial Lance.)[4]


  1. ^ a b c d Berio, P.; et al. (November 2011), "Chromosphere of K giant stars. Geometrical extent and spatial structure detection", Astronomy & Astrophysics, 535: A59, arXiv:1109.5476Freely accessible, Bibcode:2011A&A...535A..59B, doi:10.1051/0004-6361/201117479 
  2. ^ Garrison, R. F. (December 1993), "Anchor Points for the MK System of Spectral Classification", Bulletin of the American Astronomical Society, 25: 1319, Bibcode:1993AAS...183.1710G, retrieved 2012-02-04 
  3. ^ (Chinese) 中國星座神話, written by 陳久金. Published by 台灣書房出版有限公司, 2005, ISBN 978-986-7332-25-7.
  4. ^ (Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 6 月 29 日