Ophiuchus - The Serpent Holder

Ophiuchus is a summer constellation located north of Scorpius and south of Hercules. The ecliptic passes through the southern part of Ophiuchus. This makes Ophiuchus a zodiacal constellation, but is not one of the astrological signs of the Zodiac. The Milky Way passes though the southern and eastern parts of the constellation. Ophiuchus is best seen from June through August.

History and Mythology

This ancient constellation has been associated with many mythological figures. The serpent is a symbol of renovation and healing, since it sheds its skin every year. Most identify the figure holding the serpent as Asclepius, the son of Apollo and Coronis. He was educated by the centaur Chiron. Asclepius took an herb from a snake and used it to bring the dead back to life. Hades, the ruler of the underworld, became worried that there would be no more souls for him. Hades convinced Zeus to kill Asclepius, and to make all mortals eventually die. Zeus did kill Asclepius, but he placed him in the sky, along with his serpents, to honor him.

Notable Stars

Alpha Ophiuchi or Rasalhague, "the head of the serpent charmer" is the brightest star in Ophiuchus, with a magnitude of 2.8. It is located about 50 light-years away. Beta Ophiuchi has the traditional name Cebalrai, meaning "shepherd's dog" in Arabic. It is a 3rd-magnitude orange giant 82 light years away.

Epsilon Ophiuchi and Delta Ophiuchi have the traditional names Yed Posterior and Yed Prior. The name Yed means "the hand" in Arabic, as the two stars are the left hand of the Serpent Bearer. They are separated by only 1.5 degrees, but Yed Prior is 170 light years away, while Yed Posterior is a less-luminous yellow giant 108 light years away.

The most celebrated star in Ophiuchus is Barnard's Star, a 9th magnitude red dwarf, that is the second closest star to the Sun. It is named for the American astronomer Edward Barnard, who discovered its very large proper motion relative to the background stars. Barnard's Star moves by the width of the full Moon every 200 years - this is partly due to is closeness, and partly due to the fact that Barnard's Star is actually moving quickly relative to the other nearby stars in the solar neighborhood.

At 16.6 light years away, 70 Ophiuchi is the 51st closest star system to Earth. 70 Oph is double star with components of magnitude 4.2 and 6.0. They are easily separable with a small telescope, swinging from 2" to 7" apart over a period of 88 years.

Clusters, Nebulae, and Galaxies

The open cluster IC 4665 is one of the brighter open clusters in Ophiuchus. It is a conspicuous binocular object, appearing very coarse and loose in a telescope. The cluster lies about 1,400 light years from Earth, and contains 30 member stars.

Ophiuchus contains over 22 globular clusters. M 12 is a 7th magnitude globular which appears as a ball of 11th magnitude stars. It is at a distance of 16,000 light-years. M 10 is also a 7th magnitude globular similar to M12, and it is at a distance of 14,000 light-years. M 9 is a fainter 8th magnitude globular cluster, partially obscured by the Milky Way. It is at a distance of 26,000 light-years away. M 14 is an 8th-magnitude globular at a distance of about 30,000 light years.

Other Messier globular clusters in Ophiuchus include the 9th-magnitude M 19; the 7th-magnitude M 62; and the very loose globular M 107.

Ophiuchus is known for its large number of dark nebulae. These include the dark nebula B 72, known as the "snake" or as Barnard's 'S' Nebula.

IC 4603, 4604, 4605, and 4606 make up the Rho Ophiuchi nebula, is a large diffuse nebula of 5th magnitude. It is located in the southwestern corner of the constellation; the region surrounding Rho Oph, with its large number of star clusters, and bright and dark nebulae, makes spectacular photographs.

There are no prominent galaxies in Ophiuchus. NGC 6572 is a 9th-magnitude planetary nebula with an intense blue-green color. NGC 6309 is an 11th magnitude planetary nebula.