It is best visible in the northern summer and located opposite Orion in the sky. Ophiuchus is depicted as a man grasping a serpent; the interposition of his body divides the snake constellation Serpens into two parts, Serpens Caput and Serpens Cauda, which are nonetheless counted as one constellation.
RS Ophiuchi is part of a class called recurrent novae, whose brightness increase at irregular intervals by hundreds of times in a period of just a few days. It is thought to be at the brink of becoming a type-1a supernova.
Barnard's Star, one of the nearest stars to the Solar System (the only stars closer are the Alpha Centauri binary star system and Proxima Centauri), lies in Ophiuchus. (It is located to the left of β and just north of the V-shaped group of stars in an area that was once occupied by the now-obsolete constellation of Taurus Poniatovii, Poniatowski's Bull.)
The most recent interpretation is that the figure represents the healer Asclepius, who learned the secrets of keeping death at bay after observing one serpent bringing another healing herbs. To prevent the entire human race from becoming immortal under Asclepius' care, Zeus killed him with a bolt of lightning, but later placed his image in the heavens to honor his good works. It has also been noted that the constellation Ophiuchus is in close proximity in the sky to that of Sagittarius, which has at times been believed to represent Chiron (the mentor of Asclepius and many other Greek demigods), though Chiron was originally associated with the constellation Centaurus.
Another possibility is that the figure represents the Trojan priest Laocoön, who was killed by a pair of sea serpents sent by the gods after he warned the Trojans not to accept the Trojan Horse. This event was also memorialized by the sculptors Agesander, Athenodoros, and Polydorus in the famous marble sculpture Laocoön and his Sons, which stands in the Vatican Museums.
This constellation, known from antiquity, is one of the 48 constellations described by Ptolemy. It has also been known as Serpentarius, a Latin form of its name.
The most important event in Ophiuchus' history was the Supernova of 1604, which was first observed on October 9, 1604, near θ Ophiuchi. Johannes Kepler saw it first on October 16 and studied it so extensively that the supernova was subsequently called Kepler's Supernova. He published his findings in a book titled De stella nova in pede Serpentarii (On the New Star in Ophiuchus's Foot). Galileo used its brief appearance to counter the Aristotelian dogma that the heavens are changeless.
It occurred only 32 years after another supernova in Cassiopeia that had been observed by Tycho Brahe; the last supernova before then had occurred in 1054 (see Crab Nebula), and after Kepler's, no further naked-eye supernovae were observed until 1987 (see Supernova 1987a.)