If in the middle of summer we make observations of the starry sky, it is not difficult to come across three very small constellations, two of which are really right and which, once recognized, are very difficult to forget. Through the Stellarium website, we can see that the constellations of the Horse, the Dolphin and the Arrow are positioned near the constellation of the Eagle and the brilliant Altair, near that magnificent luminous track that is the Milky Way. Let's go and analyse them up close.
Thanks to Celestia we can see this class K3 star, from the distance adopted by me as standard, 10 UA, really bright and with an apparent diameter greater than 5°: always remember that from the distance of 10 UA (Saturn's distance from the Sun) our Sun appears very small, a little more than 3′, but always very bright.
Two stars of the Dolphin, α and β, have been baptized with strange names at first sight, respectively Sualocin and Rotanev: for the non enigmasters I will report the solution of the mystery at the end of the article...
Another star (ε Del) instead is called (I don't know by whom, I found the name on internet) Deneb Dulphim, the dolphin's tail, following a tradition of many constellations representing animals. As for the stars, there's nothing more to add to what little I reported: but now with the deep sky objects, our Dolphin will show all its beauty.
Deep sky objects
Let's start with a planetary nebula (NGC 6891) really suggestive: I remember that generally the photos I propose are almost always taken by the HST)
planetary nebula NGC 6891
Now we move on to two fantastic globular clusters, the first of which is NGC 6934
the globular cluster NGC 6934
while the other is NGC 7006
the globular cluster NGC 7006
Representation of the Dolphin
It's now time to see how the ancients represented this animal, starting from Hevelius
and then move on to Uranometry
only to end up with our beloved Stellarium...
The sky is a source of wonder! Most of the time hidden...
The name, history and myth of Delfino
In India its auspicious stars were associated with porpoises; the Arabs, in ancient times, called them "precious stones". The quadrilateral of the main stars is called "Job's coffin" in English. For the Greeks it was the "sacred fish". According to Eratosthenes, Poseidon, god of the sea, was tired of his lonely life and thought he was looking for a wife.
He was enchanted by the beautiful Amphitrite, a sea nymph, one of the Nereids, who however did not seem at all interested in courtship. So it was that Neptune asked a dolphin for help, who managed to convince the nymph. In gratitude, Neptune placed the dolphin in the sky in the form of a constellation.
It's not the only legend, though. Another one - sung by Igino and Ovid, sees the dolphin as the animal that saved the musician of Lesbos Arion (a historical figure who lived at the turn of the 7th-6th centuries BC) from the waters of the ocean into which he was thrown by his crew. In practice, Arion had just won a musical competition full of prizes and was returning home when the crew threw the singer into the sea to grab the prizes. When the rescuer dolphin died, the animal was brought back to life and placed in the sky for merit. Apollo, who sent the dolphin into the sky, also wanted to save the musical instrument, the Lira...
The Curious Horse
Of this constellation we can say that it is really small and rather insignificant (but obviously no object in the sky is insignificant in the eyes of an enthusiast!): it has two stars (9 Equ and 3 Equ) just over 60 times the size of our Sun, while the star δ Equ is quite close to us, with a distance of 60 light years: compared to the astronomical distances of galaxies and black holes, this star is almost around the corner, but still very far away from the distances we are used to every day.
Among the galaxies in this small area of the sky, I show you NGC 7015, really beautiful.