Constellation, Dolphin
Delphinus
The dolphin, a small, neat group of stars leaping beside the Milky Way. Two of its stars hide a Palermo astronomer’s name, spelled backwards.
From New York on October 13, 2026, the centre of Delphinus rises at 1:12 PM, is highest at 8:06 PM (64° above the horizon in the S) and sets at 3:01 AM.
In the 3D sky
The sky over New York turned towards Delphinus. Drag to look around.
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Evening visibility over the year
Height of the constellation’s centre above the horizon at 10 pm local time on the 15th of each month, from New York. Above about 30° it is well placed.
Name and history
Greek myth tells two stories of this dolphin. In one, told by Eratosthenes, the sea god Poseidon wished to marry the sea nymph Amphitrite, but she fled from him. The dolphin, sent as his messenger, found her and brought her back to become his wife, and Poseidon thanked it with a place among the stars. In the other, the poet and musician Arion was sailing home to Greece when the sailors plotted to kill him for his wealth. He sang one last song and leapt into the sea, and a dolphin carried him safely to land. Apollo then placed the dolphin in the sky.
The four stars of the dolphin’s body form a small diamond, sometimes called Job’s Coffin. Its two brightest stars are named Sualocin and Rotanev, which first appeared in the Palermo Catalogue of 1814. Read backwards they spell Nicolaus Venator, the Latin form of the name of Niccolò Cacciatore, assistant and later successor of Giuseppe Piazzi at Palermo Observatory. Cacciatore is usually said to have named them himself, but Piazzi may have chosen them to honour him.
Sources: Ian Ridpath, Star Tales: Delphinus
Brightest stars
| Star | Designation | Magnitude | Distance |
|---|---|---|---|
| Rotanev | β Del | 3.64 | 101 light-years |
| Sualocin | α Del | 3.77 | 254 light-years |
| Aldulfin | ε Del | 4.03 | 331 light-years |
| γ2 Del | γ2 Del | 4.27 | 126 light-years |
| δ Del | δ Del | 4.43 | 223 light-years |
| ζ Del | ζ Del | 4.64 | 220 light-years |
Facts
| Area | about 188 square degrees (69 of 88) |
|---|---|
| IAU abbreviation | Del |
| Sky | Near the celestial equator, visible from both hemispheres |
| Origin | Listed in Ptolemy’s Almagest, about AD 150, from older Greek tradition |
| Stars brighter than magnitude 5 | 6 |
| Centre (J2000) | 20.7 h, 15° |
Deep-sky objects
Galaxies, clusters and nebulae brighter than magnitude 9, from the OpenNGC catalogue. Most need binoculars or a telescope and a dark sky.
No deep-sky object brighter than magnitude 9.
Boundaries: International Astronomical Union, via Astronomy Engine. Areas are computed from the boundaries by sampling (within about one percent). Names and lines: Stellarium. Stars: HYG Database. Deep-sky objects: OpenNGC. Calculated with Astronomy Engine, an open-source library verified against the US Naval Observatory and NASA JPL. Data sources
How to use this page
Choose your place and a night at the top. The answer and the 3D view show where the constellation is, when it is highest and whether it rises at all from where you are. The chart shows its stars and lines, and the tables list its brightest stars and the deep-sky objects inside it.
Frequently asked questions
When is a constellation best seen?
When it is highest in a dark sky, which the page gives for the night you pick. Each constellation is best placed in a particular season, because the stars rise about four minutes earlier every night.
Why can I not see a constellation from my place?
Constellations far south of the celestial equator never rise from northern places, and those far north never rise from southern ones. The page says when this is the case.
What are the constellation boundaries?
The International Astronomical Union divides the sky into 88 areas with official boundaries. The stick figures are only a drawing aid, the boundaries say which constellation a point in the sky belongs to.
Related guides
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- Altitude and azimuth: finding things in the skyTwo angles tell you exactly where to look: which direction, and how high.
- Light pollution and dark skies: the Bortle scaleFrom a city centre you can count a few dozen stars. From a truly dark site you can count a few thousand, with the Milky Way bright enough to cast a shadow. The Bortle scale puts a number on the difference.
- Binoculars for stargazing: what to buy and what to look atA pair of 7x50 or 10x50 binoculars shows the craters of the Moon, the moons of Jupiter, dozens of star clusters and the Andromeda Galaxy, for a fraction of the cost of a telescope.