How can I see the Delphinus constellation?

Published: 13th September, 2022 at 11:00
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This small constellation represents the head and neck of a bottlenose dolphin.

There are many creatures depicted in the night sky. Some, such as Scorpius the Scorpion or Cygnus the Swan, do, with a bit of imagination, look like the thing they’re supposed to represent. Others, such as Delphinus the Dolphin, require more work.

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Delphinus is a small constellation of summer and can be seen from late July to August. It is located to the left (east) and slightly north of the summer star Altair, the brightest in the constellation of Aquila the Eagle. Altair is easily identified thanks to the two dimmer, but still bright, stars that sit either side of it; Tarazed and Alshain.

The best way to describe how Delphinus appears to the naked eye, is as a small diamond pattern with a tail. The diamond pattern is also an asterism (an unofficial pattern) known as Job’s Coffin. The constellation may not look too much like a dolphin at first, but that may be because you’re imagining it wrong. It’s supposed to represent the nose and neck of a bottle-nosed dolphin, its head poking out of the sea.

How to see the Delphinus the Dolphin constellation? © Pete Lawrence
© Pete Lawrence

Delphinus is compact, and even though its stars aren’t particularly bright, it is distinctive. The two stars on the western (right) side of the diamond have the unusual names Sualocin and Rotanev. These first appeared on the Palermo Star Catalogue of 1814, courtesy of the Italian astronomer Niccolò Cacciatore.

It took 45 years before the British astronomer Reverend Thomas Webb worked out what Cacciatore had done to create the star names. He’d Latinised the English version of his name to arrive at Nicolaus Venator and simply reversed the letters to generate the star names as a practical joke which has stuck.

The dolphin’s nose is marked by Gamma Delphini, a binary star which splits into a golden-orange primary and yellow secondary, when viewed through the eyepiece of a telescope.

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Authors

Pete Lawrence is an experienced astronomer and astrophotographer, and a presenter on BBC's The Sky at Night.

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