Ras Alhague is Alpha Ophiuchi, apparent magnitude 2.08, at roughly 48 light years. It is a white giant or bright subgiant of type A5, with a much fainter companion in a close orbit whose gravity has measurably distorted the primary. It marks the head of Ophiuchus, the serpent-bearer, the large constellation that the ecliptic actually crosses, so that the Sun passes through Ophiuchus for part of November, the fact behind the recurring popular claim of a thirteenth zodiac sign. The Arabic name, ras al-hawwa, means the head of the serpent-charmer.
The close companion distorting Ras Alhague's shape orbits in only about eight years, unusually tight for a pair involving a giant star, and the gravitational interaction between the two is thought to be slowly affecting both components' rotation, a genuinely active dynamical system rather than a simple, static double. No specific classical source beyond the general compiling tradition is known for Ras Alhague's delineation, and the star's confident modern personality reading, like so many others gathered here, is a comparatively late addition to a very old name. Its bright, central position within an otherwise sprawling and faint constellation makes Ras Alhague one of the more useful naked-eye landmarks of the summer sky.
Sources AstronomyAndrew Fraknoi, David Morrison, and Sidney C. Wolff (OpenStax) with Almagest (Mathematike Syntaxis)Claudius Ptolemy