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Rasalhague (Alpha Ophiuchi)

The brightest star in the constellation Ophiuchus; its name, which refers to the whole constellation, comes from an Arabic phrase meaning "the Head of the Serpent Collector." Rasalhague is a giant A star that has probably recently exhausted its core hydrogen reserves. It has a faint, very close companion only 0.5" away, equivalent to 7 AU in real terms, that orbits with a period of 8.7 years.

visual magnitude 2.08
absolute magnitude 1.30
spectral type A5III
surface temperature 8,500 K
luminosity 25 Lsun
mass 2 to 4 Msun
distance 47 light-years
position R.A. 17h 34m 56.1s,
Dec. +12 33' 36"

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