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Alpha Ophiuchi
Ophiuchus constellation map.png
Ras Alhague is the α star in the constellation of Ophiuchus.
Observation data
Epoch J2000      Equinox J2000
Constellation Ophiuchus
Right ascension 17h 34m 56.1s
Declination +12° 33′ 36″
Apparent magnitude (V) 2.08
Spectral type A5 III
U-B color index 0.11
B-V color index 0.15
Variable type ?
Radial velocity (Rv) +12.6 km/s
Proper motion (μ) RA: 110.08 mas/yr
Dec.: -222.61 mas/yr
Parallax (π) 69.84 ± 0.88 mas
Distance 46.7 ± 0.6 ly
(14.3 ± 0.2 pc)
Absolute magnitude (MV) 1.30
Mass 2–4 M
Radius 2.5 R
Luminosity 29.19 L
Temperature 8,500 K
Metallicity ?
Rotation ?
Age ? years
Other designations
Ras Alhague, Rasalhague, 55 Ophiuchi, Gl 681, HR 6556, BD +12° 3252, HD 159561, GCTP 4000.00, SAO 102932, FK5 656, HIP 86032.

Alpha Ophiuchi (α Oph / α Ophiuchi) is the brightest star in the constellation Ophiuchus. It has the traditional name Ras Alhague.

Ras Alhague has an apparent magnitude of +2.08, belongs to the spectral classification A5, and is about 47 light years distant from Earth.

The name Ras Alhague is from the Arabic رأس الحية (raʾs al-ḥayyah), meaning "the Head of the Serpent-charmer."



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