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Rasalhague

Ras Alhague, Alpha Ophiuchi, 55 Ophiuchi

White Star in Ophiuchus

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Proper Names	Rasalhague, Ras Alhague
Bayer Designation	Alpha Ophiuchi
Flamsteed Number	55 Ophiuchi
HR (BSC)	6556
HD	159561
Constellation	Ophiuchus
Right Ascension	17h 34m 56s
Declination	+12° 33' 36"
Distance	49 light years 15 parsecs
Magnitude	Apparent: +2.1 Absolute: +1.2
Spectral Class	A5III white giant
Optimum Visibility	June / July
Notes	Rasalhague 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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