Delphinus

Delphinus is a small constellation located in the Northern Celestial Hemisphere. It sits very close to the celestial equator. The name is the Latin version of the Greek word for dolphin. It is one of the 88 modern constellations recognized by the International Astronomical Union. This group was also listed by the astronomer Ptolemy in the 2nd century.

Although it is a recognizable pattern, it is quite small. It ranks 69th in size among all the constellations. It covers an area of 188.5 square degrees. This represents about 0.457% of the entire sky.

To find Delphinus, you can look for a distinctive asterism. An asterism is a bright pattern of stars within a constellation. In this case, five bright stars form the shape of a dolphin. Four stars represent the body, and one star represents the tail. This diamond-shaped pattern is often called Job's Coffin. It is made of the stars Alpha, Beta, Gamma, and Delta Delphini.

The constellation is bordered by several other groups. These include Vulpecula to the north and Sagitta to the northwest. Aquila sits to the west, while Pegasus and Equuleus are to the east. Aquarius borders it to the southeast.

Many ancient stories explain why this dolphin exists in the stars. One Greek myth involves the god Poseidon. He wanted to marry a beautiful nereid named Amphitrite. She fled to the Atlas Mountains to protect her virginity. Poseidon sent searchers to find her, including a dolphin named Delphinus. This dolphin found her and persuaded her to accept the god. Out of gratitude, Poseidon placed the dolphin in the stars.

Another story features the poet Arion of Lesbos from the 7th century BC. Arion was a musician traveling from Tarentum. His crew conspired against him because of his wealth. Arion jumped into the sea while singing a dirge. A dolphin was charmed by his music and carried him to the Greek coast.

Astronomers have discovered many fascinating stars within this region. The constellation is considered faint because it has few bright stars. Only two stars are brighter than magnitude 4. These are Beta Delphini, or Rotanev, and Alpha Delphini, or Sualocin. These two names are the names of astronomer Niccolò Cacciatore written backward. Alpha Delphini is a blue-white spectroscopic binary star. It is located 241 light-years from Earth. Beta Delphini is a white star located 97 light-years away. It was identified as a binary star in 1873.

Other stars like Gamma Delphini are also famous. Gamma Delphini is a true binary star with an orbital period of over 3,000 years. Its components are 125 light-years away.

Beyond stars, scientists have found many exoplanets in Delphinus. These are planets that orbit stars outside our solar system. One planet is named Arion, which orbits the star Musica. Arion is very massive, at least 10.3 times the mass of Jupiter. In 2024, researchers discovered two more planets, TOI-6883 b and TOI-6883 c. TOI-6883 b has a mass 4.34 times that of Jupiter. TOI-6883 c is a smaller, Neptunian-size planet. These discoveries often come from analyzing data from telescopes like TESS. Even the star Zeta Delphini was found to have a brown dwarf orbiting it in 2014.

Delphinus also contains beautiful deep-sky objects. Because it lies in a rich part of the Milky Way, many objects are visible with telescopes. The Blue Flash Nebula, or NGC 6905, is a notable planetary nebula. This nebula is rich in oxygen. There is also a globular cluster named NGC 6934. This is a dense group of stars located 52,000 light-years away. Another cluster, NGC 7006, is much further at 137,000 light-years. This cluster sits at the very outer reaches of our galaxy. These objects help scientists understand how galaxies and stars form over time.

Different cultures have viewed these stars in various ways. In Chinese astronomy, these stars are part of the Black Tortoise of the North. In Hindu astrology, the constellation corresponds to the lunar mansion known as Dhanishta. In Polynesia, different cultures gave the stars their own names. The people of Pukapuka called it Te Toloa. The people of the Tuamotus called it Te Uru-o-tiki. These diverse traditions show how humans have always looked to the sky to find meaning in the stars.