Alpha Ophiuchi

α Ophiuchi
Location of α Ophiuchi (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Ophiuchus
Right ascension 17h 34m 56.06945s[1]
Declination +12° 33′ 36.1346″[1]
Apparent magnitude (V) 2.07[2]
Characteristics
Spectral type A5IVnn[3] / K5–7 V[4]
U−B color index +0.10[2]
B−V color index +0.15[2]
Astrometry
Radial velocity (Rv)+12.6[5] km/s
Proper motion (μ) RA: 108.07[1] mas/yr
Dec.: -221.57[1] mas/yr
Parallax (π)67.13 ± 1.06 mas[1]
Distance48.6 ± 0.8 ly
(14.9 ± 0.2 pc)
Absolute magnitude (MV)+1.248[6]
Orbit[4]
Period (P)3,148.4 days
Semi-major axis (a)427+20
−13 mas
Eccentricity (e)0.92±0.03
Inclination (i)125+6
−9°
Longitude of the node (Ω)232±9°
Periastron epoch (T)2,452,888±53 JD
Argument of periastron (ω)
(secondary)		162±14°
Details
α Oph A
Mass2.40+0.23
−0.37[4] M☉
Radius2.858±0.015 R☉ (equatorial)
2.388±0.013 (polar)[7] R☉
Luminosity31.3±0.96[7] L☉
Surface gravity (log g)3.91[8] cgs
Temperature7,569±124 K (equatorial)
9,384±154 (polar)[7] K
Rotation0.61[7] days
Rotational velocity (v sin i)239±12[7] km/s
Age0.77±0.03[9] Gyr
α Oph B
Mass0.85+0.06
−0.04[4] M☉
Other designations
Ras Alhague, Rasalhague, 55 Ophiuchi, BD+12° 3252, FK5 656, HD 159561, HIP 86032, HR 6556, SAO 102932.[10]
Database references
SIMBADdata

Alpha Ophiuchi (α Ophiuchi, abbreviated Alpha Oph, α Oph), also named Rasalhague /ˈræsəlheɪɡ/,[11][12] is a binary star and the brightest star in the constellation of Ophiuchus.

  1. ^ a b c d e Cite error: The named reference aaa474_2_653 was invoked but never defined (see the help page).
  2. ^ a b c Cite error: The named reference clpl4 was invoked but never defined (see the help page).
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  7. ^ a b c d e Cite error: The named reference monnier was invoked but never defined (see the help page).
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  11. ^ also /-ˈheɪɡjuː/ or /-ˈheɪɡwiː/.
    "Rasalhague". Merriam-Webster.com Dictionary. Merriam-Webster.
  12. ^ Kunitzsch, Paul; Smart, Tim (2006). A Dictionary of Modern star Names: A Short Guide to 254 Star Names and Their Derivations (2nd rev. ed.). Cambridge, Massachusetts: Sky Pub. ISBN 978-1-931559-44-7.