Observing Serpens the Snake
The Constellation Home to the Famous Eagle Nebula
Serpens the Snake is divided into two halves and contains one Messier object in each portion: a famous nebula and a globular cluster.
Serpens the Snake is associated with the constellation Ophiuchus, the snake handler. Ophiuchus is a large constellation that is holding Serpens, and Serpens can be found divided into two sections of sky on either side of Ophiuchus.
Locating the Constellation Serpens
Because Serpens is divided into two halves it is sometimes given two names. The eastern portion of the constellation is known as Serpens Cauda and the western half is Serpens Caput. Serpens Cauda is found in the summer sky sandwiched between Ophiuchus, Sagittarius, Aquila, and Scutum. The portion of sky is a skinny, snaky patch that contains few bright stars or notable objects except for M16, the Eagle Nebula.
The western half of Serpens, Serpens Caput, is also seen in summer skies and lies off the northwestern portion of Ophiuchus next to Bootes (not far from the bright star Arcturus). In Serpens Caput is one Messier object, a globular cluster known as M5, one star above 3rd magnitude, and one well-known galaxy cluster.
The Eagle Nebula in Serpens Cauda
The Eagle Nebula has become famous due to stunning Hubble photographs that peer deep inside the collection of gas and dust. You can find the Eagle Nebula in the southeastern corner of Serpens Cauda, about 12 degrees above the top of the teapot asterism in Sagittarius. The Eagle Nebula, M16, shines at magnitude 6 and can be spotted in small instruments or binoculars. M16 consists of both a star cluster and the notable nebula. The gas in the nebula forms pillar-like shapes and contains a stellar nursery, where new stars are forming about 7,000 light-years away from Earth.
Targets in Serpens Caput
The one bright star in Serpens Caput is located in the middle of this portion of the constellation. Alpha Serpentis is magnitude 2.63 and lies 73 light-years away. It also goes by the name Unukalhai, which means "neck of the snake". It is sometimes also called Cor Serpentis, which means the "heart of the serpent".
A little less than eight degrees to the southwest of Alpha is the globular cluster M5. M5 is magnitude 5.8, easily spotted in a pair of binoculars. It lies about 24,500 light-years away.
Toward the top of the constellation Serpens Caput is a favorite target for deep-sky observers with larger scopes. NGC 6027 is a galaxy cluster with the name of Seyfert's Sextet. At magnitude 12.4, this gathering of six galaxies reveals itself only to the seasoned observer. These galaxies lies about 190 million light-years away.
