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Ras Alhague, Alpha Ophiuchi, 55 Ophiuchi

Proper NamesRasalhague, Ras Alhague
Bayer DesignationAlpha Ophiuchi
Flamsteed Number55 Ophiuchi
HR (BSC)6556
Right Ascension17h 34m 56s
Declination+12° 33' 36"
Distance49 light years
15 parsecs
MagnitudeApparent: +2.1
Absolute: +1.2
Spectral ClassA5III white giant
Optimum VisibilityJune / July
NotesRasalhague is a binary star with a very close companion. The main white giant is orbited by a dwarf star with only about an eighth the mass of its primary, at a distance of about 7 AU (closer than Saturn is to the Sun). The dwarf companion completes each orbit of the primary star over a period of a little under nine years.
Relative Galactic Position of Rasalhague

The Galactic position and direction of Rasalhague relative to Earth's Sun. Note that, at this extreme scale, the two stars are effectively in the same place.

This white star is the brightest in the constellation of Ophiuchus, the Serpent Holder, and its name means 'Head of the Serpent Holder'. Its variable brightness and peculiarities in its spectrum suggest that it may be surrounded by a dense cloud of material.


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