It is an interesting fact that there are three brightest stars in the constellation. They are Rotanev, Beta and Delphini. Delphini further has five stars. Delphinus or the Dolphin is a small constellation in the northern hemisphere. It is said that one of the oldest stars Rho Aquilae, which is about 50 million years old had belonged to the constellation Aquila until 1992 and later crossed the border and moved to Delphinus. It was first catalogued by the Greek astronomer Ptolemy in the 2nd century. Also, Delphinus was sometimes referred to as the Job’s Coffin due to its long and box–like shape. It belongs to the Heavenly Waters family of constellations and is clearly visible in the month of October.

Which stars comprise the constellation?

Delphinus contains five stars with known planets. Some of its major stars include:

  • α Delphini or Alpha Delphini: It is the brightest star of this constellation. With a combined apparent magnitude of about 3.77, it consists of seven components namely A and G, B, C, D, E and F. Niccolò Cacciatore, an Italian astronomer named it Sualocin as it is a Latinized version of his name spelled backwards.
  • β Delphini ro Beta Delphini: This star was properly named as Rotanev by Cacciatore as it is a Venator version of the name spelled backwards. Also, it is a Latinized version of his family name meaning ‘the hunter’. Discovered as a binary star in 1873, it is about 1.8 million years old and is nearly 101 light years distant.
  • y Delphini or Gamma Delphini: It is a binary star with a magnitudes of about 5.14 and 4.27. A yellow–white dwarf of the spectral type F7V is its primary component. Its companion star is an orange sub giant that belongs to the spectral class K1IV.
  • δ Delphini ro Delta Delphini: It is  a giant star that belongs to the spectral class A7IIIp. Classified as a Delta Scuti variable, it has a visual magnitude of about 4.434.
  • ε Delphini (Epsilon Delphini): It is  a blue–white giant star that belongs to the spectral class B6III. Its traditional name is Debeb Dulfim, which is derived from the Arabic word ðanab ad–dulfīn meaning ‘the dolphin’s tail’. This name was later translated into a Latin name Cauda Delphini. With a visual magnitude of about 4.03, it is about 358 light years distant.
  • Tso Ke–ρ Aquilae (Rho Aquilae): It is a white main sequence dwarf.
Does it contain any deep objects or galaxies?

It has numerous deep sky objects, some of the notable ones are:

  • NGC 6934 or Caldwell 47: This is a large globular cluster near Epsilon Delphini star. With a visual magnitude of about 8.83, it is approximately 50,000 light years distant.
  • NGC 6891: It is a small planetary nebula with a visual magnitude of about 10.5.
  • Blue Flash Nebula or NGC 6905: It is another small planetary nebula which is bluish in colour.
  • NGC 7006 or Caldwell 42: Another globular star cluster, it is a part of a region in the Milky Way known as galactic halo.
What is its position in the galaxy?

Seen at latitudes between +90° and -70°, it lies in the fourth quadrant of the northern hemisphere.

How much space does it occupy in the sky?

It occupies an area of 189 square degrees, making it the 69th constellation in the sky.  The star furthest away in this constellation is 241 light years away from earth. Hence, it can be said that Delphinus constellation is 241 light years distant from the earth. 

What is the cultural or mythological significance of Delphinus?

According to a certain myth, Delphinus represents Poseidon, the sea god’s messenger.  When Poseidon was courting Amphitrite, in one instance, she resisted his moves by taking refuge among her sisters. Poseidon, in order to bring her back, sent numerous messengers to find her. One among them was a dolphin who calmed Amphitrite and brought her back. As an honour, the sea god placed this dolphin in the sky as a star. According to another mythological story, the god of poetry and music Apollo placed a dolphin as a star in the sky as it saved the life of Arion. Arion was a poet and a musician who was famous in 7th century BC.

Which are its neighbouring constellations?

Delphini borders constellations like Aquarius, Aquila, Equuleus, Pegasus, Sagitta and Vulpecula. 

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