What is the constellation Delphinus?
Dolphin (Delphinus) is a small boreal constellation very close to the celestial equator. It is one of the 48 constellations cataloged by Ptolemy.
It looks remarkably like a dolphin, making it easy to recognize in the sky. Delphinus is surrounded by the Guineueta, the Saeta, Águila, Aquarius, the Little Horse and finally the flying horse: Pegasus.
Delphinus main stars
Sualocin (α Delphini)
Sualocin, the star α of the Dolphin constellation (which is slightly less bright than β), does not exceed the apparent magnitude 3.77. It is a white star that rotates very quickly on itself (70 times faster than the Sun).
Sualocin It is a double star: the two stars that form it are at a distance of 12 AU from each other, and its orbit lasts 17 years.
Rotanev (β Delphini)
The brightest star in the Dolphin constellation is the star β, which is known as Rotanev since 1814.
Rotanev is a double star, composed of two subgegants of magnitude 4.0 and 4.8, separated from each other by 13 au on average, and orbiting in 26.7 years.
The names of Sualocin and Rotanev They have an unusual origin: they appear for the first time in the catalog of stars published by the Palermo observatory in 1814, and come from Nicolaus Venator spelled backwards, the Latinized name of Niccolò Caccicatore (Caccicatore and Venator mean hunter), the deputy director of that observatory at the time of the catalog’s publication.
Other stars
γ Delphini is a double star where the components are separated between 600 and 40 au. α, β, γ, and δ Delphini form the asterism called Job’s bier.
Deneb Dülfer (ε Delphini), an Arabic name meaning the tail of the Dolphin, is located at the end of the constellation.
R Delphini is a variable star of the Mira type (constellation of the Whale) that passes from magnitude 7.6 to 13.8 in 285.5 days.
Notable Delphinus Deep Sky Objects
NGC 6891
NGC 6891 is planetary nebula. This type of nebula is formed by incandescent gas and expanding ionized plasma ejected during the asymptotic giant branch phase, that is, a gaseous astronomical object formed from the ejection of the outer layers of a low or intermediate mass star during the final stage of his life. This name originated with their first discovery in the 18th century due to the fact that, observed with small optical telescopes, they appeared similar to the giant planets of the solar system. The initial star, which remains in the central part of the nebula, becomes a white dwarf that eventually cools until it loses its residual thermal energy. The upper limit in mass to go through this stage of stellar evolution is 8 solar masses. Higher mass stars have a completely different evolution: they explode as a type II supernova and collapse, forming a neutron star or black hole. They are a relatively short-lived phenomenon, lasting only a few tens of thousands of years compared to the typical lifespan of stars of several billion years.
NGC 6891 has a magnitude of 10.5.
NGC 6934
This globular cluster is of magnitude 0.75. A globular cluster is a spherical group of old stars (star cluster) that orbits a galaxy as if it were a satellite. The orbit they occupy is generally a spherical or elliptical volume, also in the case of spiral galaxies (the stars of which are confined in a disk).
NGC 7006
At a distance of 185,000 light years, this globular cluster is very remote, and is magnitude 11.5.