Serpens

This constellation bears the name of the Serpent that Ophiuchus carries and it appears on both sides of him. With this in mind the constellation is then in two parts (Serpens Caput and Serpens Cauda) with a total area of 637º sq. It is one of the star groups contained in the Almagest of A.D. 150. Ptolemy assigned eighteen stars to it. The first portion is a scattered star group north of Libra which culminates at midnight around May 17th.

The second portion is mostly in the Milky Way between Ophiuchus and Sagittarius. This portion culminates around June 21st.

Contained within Serpens are five open clusters with the most notable being NGC 6611(M16). This cluster is also associated with the gaseous nebula IC 4703. There are also five globular clusters within Serpens, two being very difficult and the others quite interesting, in particular is NGC 6535 And NGC 6539.

Extragalatic nebulae in Serpens are all fairly faint being around the 12.0-13.0 mag mark. However there are a couple of galaxies that can prove quite interesting to observe. A list of some of the more notable deep sky objects in Serpens appears below.

SEYFERTS SEXTET (NGC 6027)

This remarkable compact group of 5 galaxies was originally discovered in 1882 by Edouard Stephans, who was the director of the Marseilles Observatory; he used an 80cm reflector but could only log it as one entry. Visually he could not split the individual galaxies. It henceforth received a single NGC entry as NGC 6027.

In 1951 Carl Seyfert found that it was a very tight little compact group of galaxies while looking at a Schmidt plate. Seyferts Sextet is also one of the most famous groups in the Paul Hickson Catalogue and has the designation of Hickson 79. This group is so tightly packed that the whole mess could fit into our Milky Way galaxy.

For amateurs the group is fairly difficult to split, but if you have a fair sized telescope and get out into a dark site you should not have any problem observing this fascinating group. R.A.15 59 11.9 DEC+20° 45 31

Steve Gottlieb observing report from the NGC/IC database is as follows-

"NGC 6027 = (U10116) = MCG +04-38-005 = (CGCG 137-010) = VV 115 = HCG 79b = Seyfert's Sextet = PGC 56575

15 59 12.5 +20 45 49

V = 14.3; Size 0.4x0.2; Surf Br = 11.7

18" (8/3/05): at 257x, the brightest component of Seyfert's Sextet appeared faint, very small, slightly elongated ~E-W, 15"x10", contains a faint stellar nucleus with direct vision. A mag 14.5 star lies 1' ESE and two additional mag 14.5 stars lie close SE. Just resolved from HCG 79C which lies 22" west of center.

13" (5/26/84): faint, very small, irregularly round, weak concentration.

Seyfert's Sextet was discovered by Edouard Stephan (XII) in 1882. Seyfert's name was attached after a paper in 1951. Although Stephan recorded this ultra-compact group as only a single object, the description "eF, vF* inv, 2 vF st nr" implies he resolved two or probably three members.

The GSC position (15 59 12.5 +20 45 49) refers to HCG 79b (most prominent visually). The RNGC does not follow Seyfert's original designations for the members of the group."

PALOMAR 5

Palomar 5 was discovered by Walter Baade in 1950, and independently found again by A.G. Wilson in 1955. Wilson named it the Serpens Globular Cluster, not necessarily a happy naming because Serpens also contains four more globulars, including famous M5. He published its discovery together with that of Palomar 3, Palomar 4 and Palomar 13, and two new Local Group galaxies.

G.O. Abell (1955) catalogued them with their Palomar numbers. Apparently unaware or unsure about its classification as a globular, it was temporarily taken for a nearby dwarf galaxy, of elliptical or spheroidal type, named the Serpens Dwarf, and suspected to be a Local Group member candidate because of its resolution into stars.

It was found that Palomar 5 is currently undergoing a process of tidal disruption by the gravitation of the Milky Way galaxy. Many former cluster member stars are moving away from it, forming tails in opposite directions which probably exist already for several billion years, and extends now over a length of over 13,000 light years. R.A.15 16.1 DEC-00 07

RT SERPENTIS

A peculiar variable star which is sometimes classed as a slow novae. It has been questioned as to whether it could be classed as a nova at all. It was discovered by Max Wolf in Europe and also by E E Barnard at Yerkes, the later independently. It was first noted on a photographic plate made in 1909. Previous plates did not show it at all. RT Serpentis brightened slowly and reached mag 11.0 in 1910 and then increased to mag 9.0 by August 1913. It remained at this magnitude for some 10 years and then it slowly decreased in brightness reaching mag 16.0 by 1963 which apparently was its original magnitude. R.A.17 39 51.9 Dec -11 56 38

β SERPENTIS

This is a wide visual yet difficult to observe due to the brightness of the primary compared to the faint companion: 3.0, 9.2; PA 265º, separation 30.8". R.A.15 46.2 DEC+15 25

θ SERPENTIS

(Struve 2417) is a wonderful binary of two white stars: 4.0, 4.2; 103º, 22.2". R.A.18 56.2 DEC+04 11

STRUVE 2375

Quite a superb pair: 6.2, 6.6; 116º, 2.4". R.A.18 45.5 DEC+05 30.

CLEAR SKIES

References: Astronomy 2009, NGC/IC Database, the Constellations web page, NED.

Gary Kronk's Cometography