Rasalhague (Alpha Ophiuchi)

Rasalhague (Alpha Ophiuchi) is 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 astronomical units (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 RA 17h 34m 56.1s,
Dec +12° 33' 36"