Serpens is the only constellation which is usually divided into two parts, Serpens Caput (the head) followed two hours later by Serpens Cauda (the tail). They are separated by the large constellation of Ophiuchus. Ophiuchus (the serpent bearer) is usually considered to be Asclepius, the Greek god of medicine. He has a serpent coiled round his waist because, according to a myth, a snake brought him a magical herb which revived Glaucus, the young son of King Minos of Crete, who had drowned in a jar of honey. For the same reason, the rod of Asclepius, the symbol of medicine, has a snake coiled round it. The seven main stars of Ophiuchus form an irregular pentagon, an asterism called the Coffin. While most of these stars are second magnitude, the shape is not easy to make out in the semi-twilight of a summer’s night. The brightest star is Rasalhague (Alpha Ophiuchi), a hot rapidly rotating A-type star, magnitude 2.1. Its name means “the head of the serpent-collector” in Arabic. While the stars of Serpens (assisted by Nu Ophiuchi) make a pleasing snake-like shape, they are mostly third magnitude and practically invisible to the naked eye, at least in Havering.

Serpens Caput contains the globular cluster Messier 5 [1] which is bright (magnitude 5.6), although it is a considerable 24,500 light-years distant. It is estimated to be 10.6 billion years old and contains a significant number of RR Lyrae variables. It was discovered by the German astronomer Gottfried Kirch in 1702. Over in the south-eastern corner of Serpens Cauda is Messier 16 [2], better known as the Eagle Nebula because of its bird-like shape in larger telescopes (see image). It is an emission nebula with an associated star cluster. It contains the star-forming pillars of gas and dust made famous by the Hubble Space Telescope, called “The Pillars of Creation”. Even now, the young stars within this cloud are pushing the cold gas away and eventually (after millions of years) it will become an ordinary star cluster like the Pleiades.

Serpens contains two nice, but different, double stars. Delta Serpentis, in Serpens Cauda, is a tight pair of yellow-white stars, which are magnitude 4.2 and mag. 5.2. By contrast Alya at the end of the tail of Serpens Cauda is a fairly wide pair of white stars, which may be seen with tints. The magnitudes of the pair are 4.6 and 5.9.

Ophiuchus contains a number of globular clusters. Messier 12 [3], at magnitude 6.7, is dimmer than Messier 5 and it is closer, being 16,440 light-years distant. It is a very ancient cluster being estimated at 13.8 billion years old (hence notionally older than the Universe). Its neighbouring globular cluster three degrees to the east is Messier 10 [4]. It is about the same magnitude as Messier 12 and lies 14,300 light-years from us. The age of M10 lies between M5 and M12 at 11.4 billion years. It is also worth seeking out Messier 19, although it is very low in the sky. It lies just three degrees west of 36 Ophiuchi (see below). It is magnitude 6.8, about the same as M10 and M12 but extinction will make it seem dimmer. M19 is far away from us at 28,799 light-years and is 11.9 billion years old.

There are two worthwhile star clusters in Ophiuchus. IC 4665 [5] is close to Cebalrai (Beta Ophiuchi) and is a naked-eye cluster in a dark area as its magnitude is 4.2. However, although it only 55 million years old, it is very loose and probably for that reason, it was not noted by Charles Messier. NGC 6633 [6], on the western edge of the constellation, has the same magnitude as IC 4665 and it is the same size as the full moon, but is also rather sparse. It is just over 1,000 light-years away and is 660 million years old. Rho Ophiuchi [7], in the south-western corner of the constellation close to Scorpius, is a tight binary (magnitudes 5.1 and 5.7) with two wide companions, but more interestingly it is embedded in the Rho Ophiuchi cloud, which is a complex of several nebulae formed by a gas cloud. This nebulosity is obvious even in a small telescope. Barnard’s Star [8] is famous for its large proper motion—it moves by the width of the full moon every 175 years—and it is one of the closest stars to us, being only 6 light-years distant. Despite this proximity (closer than Sirius) it is only magnitude 9.5, because it is a red dwarf.

Ophiuchus also has several interesting double stars. 70 Ophiuchi [9] is near Barnard’s star. It is a binary with two orange stars (mag. 4.2 and 6.7) with a good separation. It has a short orbital period of 88 years and only has a easily resolved separation because it is so close to us (16.7 light-years). 70 Ophiuchi forms a triangle with two other stars (67 and 68 Ophiuchi) which is the lower half of the former constellation Taurus Poniatovii, named in honour of King Stanisław II August, King of Poland and Grand Duke of Lithuania, by Marcin Odlanicki Poczobutt in 1777. Just as Poland disappeared during his reign, so has the constellation, already falling of use by the early nineteenth century although it made an appearance in Urania’s Mirror of 1825. Barnard’s star is close to the right horn of the bull, 66 Ophiuchi. 61 Ophiuchi [10], below Cebalrai, is a pair of yellow-white stars of similar brightness (mag. 6.1 and 6.5). The other two doubles are in the south of the constellation and are close to Theta Ophiuchi (mag. 3.3). 39 Ophiuchi [11] a golden yellow star (mag. 5.2) with a blue companion (mag. 6.6). Two and a half degrees further south lies 36 Ophiuchi, a binary with two equally bright golden yellow stars (mag. 5.1).

The above four images are schematic representations