A little summer constellation known as Delphinus is a favorite for its close resemblance to a dolphin.
The constellation of Delphinus the Dolphin was named after a character from Greek myth. One story has Delphinus as a messenger of Poseidon, sent to the sea nymph Amphitrite to retrieve her for marriage to Poseidon. In another story he saves Arion when he is attacked by robbers on a ship.
Location
Delphinus can be found under the southeast edge of the Summer Triangle, between Deneb in Cygnus and Altair in Aquila. The constellation is best seen in summertime and early fall. The stars form a kite shape with a tail, which can appear to look like a dolphin leaping out of the water.
Stars
The brightest star is the magnitude 3.64 Beta Delphini, also known as Rotanev. It lies 97 light-years away and marks the end of the dolphin's body where it connects with the tail. The second brightest star is the magnitude 3.77 Alpha Delphini, also known as Sualocin. It lies 240 light-years away and marks the back of the dolphin. These two stars' names are a puzzle, named by the Italian astronomer Nicolaus Venator. The stars are the astronomer's first and last names spelled backward.
The nose of Delphinus is marked by the star Gamma Delphini. Gamma is a double star, with the brighter star at magnitude 4.26 and the dimmer at magnitude 5.15. They lie approximately 102 light-years away. The belly of the dolphin is marked by Delta Delphini, a magnitude 4.43 star lying 203 light-years away.
These four stars of the body of Delphinus are also sometimes called Job's Coffin.
The tail of the dolphin is marked by the star Epsilon Delphini, a magnitude 4.03 star lying 359 light-years away. A few other 4th and 5th magnitude stars can be found within the constellation's borders.
Deep-Sky Objects
Most of the deep-sky objects in Delphinus are quite dim. The brightest of these is a globular cluster found about 4 degrees out from the tail. NGC 6934 shines at magnitude 8.9. Another globular cluster, NGC 7006, can be found off the nose of the dophin if you draw a line from the back through the nose and extend it three and a half degrees. NGC 7006 is magnitude 10.6.
Two planetary nebulae can be found within the northwest boundaries of the constellation. Both are 12th magnitude. NGC 6905 is located directly above the dolphin's back and NGC 6891 is above Delphinus's tail.
A number of galaxies are scattered about Delphinus, however, most of them are 12th magnitude and dimmer, making them very hard to spot without a large telescope.
