Ophiuchus

Ophiuchus (the serpent bearer) is one of the 88 modern constellations, and was also one of the 48 listed by Ptolemy. Of the 13 modern zodiac (constellations of the ecliptic), Ophiuchus is the only one which is not counted as an astrological sign.

Ophiuchus is depicted as a man supporting a snake, Serpens; the interposition of his body divides the snake into two parts, Serpens Caput and Serpens Cauda, which are nonetheless counted as one constellation.

Notable features

The brightest stars in Ophiuchus include α Ophiuchi, called Rasalhague, at the figure's head; and λ Ophiuchi, a triple star, at his elbow.

RS Ophiuchi, a star too faint to interest amateur skywatchers, is part of a strange class called recurrent novas, whose brightness increases at irregular intervals by hundreds of times in the space of a few days.

Barnard's Star, the fifth-nearest star to the Solar System, lies in Ophiuchus.

Notable deep-sky objects

Ophiuchus contains several star clusters, such as IC 46645, NGC 6633, M9, M10, M12, M14, M19, M62, and M107, as well as the nebula IC 4603-4604. The unusual double galaxy NGC 6240 is also in Ophiuchus.

Mythology

The figure is supposed to represent the legendary physician Asclepius, who learned the secrets of life and death from serpents. In order to avoid the human race becoming immortal under Asclepius's care, Zeus killed him with a bolt of lightning, but placed him in the heavens to honour his good works.

It is not, however, easy to find the figure of a man in these stars without some diligence.

History

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 historical event in Ophiuchus was the supernova whose explosion appeared on October 10, 1604, near θ Ophiuchi. It was observed by Johannes Kepler, whence comes its name Kepler's Star. Kepler published his findings in a book entitled 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, and after Kepler's no further supernovae were observed until 1987 (see Supernova 1987a.)

Astrology

Although it is found on the plane of the ecliptic, Ophiuchus, unlike the other twelve constellations of the zodiac, did not give its name to one of the twelve equal-sized regions of sky through which astrologers reckon the planets, Sun, and Moon to travel. It is therefore not one of the twelve signs of the zodiac in modern astrology.