A saguaro under the stars, including a smudge of the Milky Way, at the Broadway Trail Head at Saguaro National Park Rincon Mountain District.

Kelly Presnell / Arizona Daily Star

Ophiuchus the Serpent Holder is directly south at 9:30 p.m. Thursday, July 13, and 40-60 degrees above the horizon. It is a large, important constellation, but it does not seem to get as much attention as it deserves, maybe because of its somewhat unusual name.

Ophiuchus is supposed to be a man holding a gigantic snake represented by Serpens Caput (head) on its western end and Serpens Cauda (tail) on its eastern end. Ophiuchus is a misshapen oval with lines of stars (the Serpens) on either end. Ophiuchus is most deserving of our attention, because it and Serpens Cauda are contiguous to the western edge of the Milky Way. Ophiuchus is one of the 13 constellations that cross the ecliptic, the sun’s apparent path in the sky.

Most of the planets’ paths around the sky are confined to the narrow zone known as the zodiac which stretches about 9 degrees on either side of the ecliptic. There are 12 main “zodiacal constellations” which cross the ecliptic.These “signs of the zodiac” were established several thousand years ago when astrology and astronomy were closely related. However, modern astronomers no longer follow the tenets of astrology, and the two disciplines have gone their separate ways. Formal constellation names and boundaries were standardized by the International Astronomical Union (IAU) in 1933 to prevent confusion. In this process, the zodiac gained a 13th constellation, Ophiuchus, because its modern boundary overlaps the zodiac.