Beta Delphini

Lore & Background

The name Rotanev originated from a practical joke by Niccolò Cacciatore, assistant and later successor to Giuseppe Piazzi at the Palermo Observatory. The name first appeared in Piazzi's Palermo Star Catalogue published in 1814, attached to Beta Delphini. The Reverend Thomas Webb, a British astronomer, eventually deduced that Rotanev is the reverse of 'Venator,' the Latinized form of 'Hunter' (Cacciatore's surname in English). The companion star Alpha Delphini received the similarly reversed name Sualocin. How Webb arrived at this explanation 45 years after the catalogue's publication remains a mystery. When the Catalogue was published in 1814, the unfamiliar names Sualocin and Rotanev were attached to Alpha and Beta Delphini, respectively. Beta Delphini was identified as a binary star system in 1873 by American astronomer S. W. Burnham. The two F-type stars orbit each other with a period of 26.66 years and an eccentricity of 0.36. The orbital plane is inclined 61° to Earth's line of sight, and the stars have an angular separation of about 0.44 arcseconds, making them challenging to resolve telescopically. The primary component is a giant star with 1.75 times the Sun's mass and 24 times its luminosity. The secondary is a subgiant with 1.47 solar masses and about 8 times the Sun's luminosity. The system is approximately 1.8 billion years old. In Chinese astronomy, Beta Delphini is part of an asterism called 瓠瓜 (Hù Guā), meaning 'Good Gourd,' which also includes Alpha, Gamma2, Delta, and Zeta Delphini.

Reader's Guide

Beta Delphini holds significance as the brightest star in Delphinus and as a binary system discovered in 1873 by S. W. Burnham. Its historical name Rotanev, along with Sualocin for Alpha Delphini, represents a notable case of a star name derived from a personal joke by Niccolò Cacciatore, whose Latinized name 'Nicolaus Venator' was reversed. The mystery of how Reverend Thomas Webb unraveled this 45 years after the 1814 Palermo Star Catalogue adds to its lore. In 2016, the International Astronomical Union's Working Group on Star Names officially approved Rotanev for the component Beta Delphini A, attributing proper names to individual stars rather than entire systems. The binary's orbital parameters—26.66-year period, 0.36 eccentricity, and 61° inclination—along with the physical properties of its F-type components (a giant and a subgiant), provide a well-characterized system for study. Its inclusion in the Chinese asterism 'Good Gourd' further connects it to cultural astronomy.

Did You Know?

• Beta Delphini is the brightest star in the constellation Delphinus.
• The name Rotanev is derived by reversing the letters of 'Venator,' the Latinized form of 'Hunter,' from Niccolò Cacciatore's surname.
• The binary system was discovered in 1873 by American astronomer S. W. Burnham.