the dolphin · pronounced del-FYE-nus. Delphinus is a small northern constellation whose four-star diamond, Job’s Coffin, and short tail suggest a leaping dolphin. It lies just east of Altair and is best seen on late-summer and early-autumn evenings. Despite its modest size, the balanced third- and fourth-magnitude pattern is unusually easy to recognize under suburban skies. Ptolemy included Delphinus among the ancient 48. Greek traditions connected the dolphin either with the rescue of the poet Arion or with the animal that helped Poseidon find Amphitrite; surviving sources preserve more than one explanation. The odd-looking names Sualocin and Rotanev encode the reversed Latinized name of Nicolaus Venator, assistant to the astronomer Giuseppe Piazzi, a nineteenth-century scholarly prank now embedded in star nomenclature. Telescopes reveal the compact globular cluster NGC 7006 far out in the Galactic halo and the closer NGC 6934. Delphinus is an official IAU region, while Job’s Coffin is an informal Western asterism contained inside it. Its near-equatorial position makes it observable from most inhabited latitudes.
About Delphinus
Delphinus is one of the 88 constellations recognized by the International Astronomical Union. Its standard three-letter abbreviation is Del, and astronomers use the genitive form Delphini when naming stars associated with it. The constellation's reference position lies around right ascension -3.4 hours and declination +6 degrees.
Its location places it in the celestial equator. For a typical mid-latitude observer, this part of the celestial sphere is especially well placed during summer evenings. Exact visibility depends on latitude, local horizon, date and time.
History and mythology of Delphinus
Historical origin
Despite its modest size, the balanced third- and fourth-magnitude pattern is unusually easy to recognize under suburban skies. Ptolemy included Delphinus among the ancient 48.
The modern constellation
Delphinus became one of the 88 official constellations standardized by the International Astronomical Union. Its boundary is a coordinate-defined sky region, while the familiar line figure joins only selected stars and has no physical depth.
Reading the cultural record
Names and stories attached to this part of the sky changed across languages, periods and communities. Cultural parallels should be identified from specialist sources rather than presented as interchangeable versions of Delphinus.
How to find Delphinus
- Use a location-aware chart and observe when Delphinus reaches its highest evening altitude; check that the full constellation rises from your latitude.
- Locate Rotanev, magnitude 3.6, then compare its direction with a brighter neighboring constellation rather than relying on line art alone.
- Trace the main pattern toward Sualocin; binoculars reveal the fainter connecting stars while preserving a wide field.
- Move to NGC 7006 with a low-power eyepiece or binoculars, then increase magnification only if its surface brightness permits.
Bright stars in Delphinus
Rotanev
Notable star- Magnitude
- 3.6
- Distance
- 97 ly
A multiple star forming the southwest corner of Job’s Coffin.
Sualocin
Notable star- Magnitude
- 3.8
- Distance
- 254 ly
A multiple system at the northwest corner; its name and Rotanev spell Nicolaus Venator backwards.
Gamma Delphini
Notable star- Magnitude
- 3.9 combined
- Distance
- about 100 ly
A beautiful wide binary with yellow-orange components.
Deep-sky objects in Delphinus
NGC 7006
A remote, compact halo cluster roughly 135,000 light-years from Earth.
NGC 6934
A moderately concentrated globular cluster discovered by William Herschel.
NGC 6891
A small, high-surface-brightness planetary nebula suited to higher magnification.
Interesting facts about Delphinus
- Delphinus’s traditional name refers to dolphin, while its official IAU boundary defines a precise region of the sky.
- Rotanev, at magnitude 3.6, is a key star in Delphinus. A multiple star forming the southwest corner of Job’s Coffin.
- NGC 7006 is a notable globular cluster in Delphinus. A remote, compact halo cluster roughly 135,000 light-years from Earth.
- NGC 6934, a globular cluster, is another observing target within the constellation.
- Despite its modest size, the balanced third- and fourth-magnitude pattern is unusually easy to recognize under suburban skies.