Beta Delphini (β Delphini, abbreviated Beta Del, β Del) is a

binary star A binary star is a system of two stars that are gravitationally bound to and in orbit around each other. Binary stars in the night sky that are seen as a single object to the naked eye are often resolved using a telescope as separate stars, in ...

in the constellation of Delphinus. It is the brightest star in Delphinus. The two components of the system are designated Beta Delphini A (officially named Rotanev , which is historically the name of the system) and B.

Nomenclature

''β Delphini'' ( Latinised to ''Beta Delphini'') is the binary's

Bayer designation A Bayer designation is a stellar designation in which a specific star is identified by a Greek or Latin letter followed by the genitive form of its parent constellation's Latin name. The original list of Bayer designations contained 1,564 stars. T ...

. The designations of the two components as ''Beta Delphini A'' and ''B'' derive from the convention used by the Washington Multiplicity Catalog (WMC) for

multiple star system A star system or stellar system is a small number of stars that orbit each other, bound by gravitational attraction. A large group of stars bound by gravitation is generally called a ''star cluster'' or ''galaxy'', although, broadly speaking ...

s, and adopted by the

International Astronomical Union The International Astronomical Union (IAU; french: link=yes, Union astronomique internationale, UAI) is a nongovernmental organisation with the objective of advancing astronomy in all aspects, including promoting astronomical research, outreach ...

(IAU). Beta Delphini bore an historical name, ''Rotanev'', which arose as follows:

Niccolò Cacciatore Niccolò Cacciatore (; 26 January 1770 – 28 January 1841) was an Italian astronomer. Cacciatore was born at Casteltermini, in Sicily. While studying mathematics and physics in Palermo, he became acquainted with Giuseppe Piazzi, head of the ...

was the assistant to Giuseppe Piazzi, and later his successor as Director of the Palermo Observatory. The name first appeared in Piazzi's Palermo Star Catalogue. When the Catalogue was published in 1814, the unfamiliar names ''Sualocin'' and ''Rotanev'' were attached to '' Alpha'' and ''Beta Delphini'', respectively. Eventually the Reverend Thomas Webb, a British astronomer, puzzled out the explanation. Cacciatore's name, ''Nicholas Hunter'' in English translation, would be Latinized to ''Nicolaus Venator''. Reversing the letters of this construction produces the two names. They have endured, the result of Cacciatore's little practical joke of naming the two after himself. How Webb arrived at this explanation 45 years after the publication of the catalogue is still a mystery. In 2016, the

organized a

Working Group on Star Names The International Astronomical Union (IAU) established a Working Group on Star Names (WGSN) in May 2016 to catalog and standardize List of proper names of stars, proper names for stars for the international astronomical community. It operates under ...

(WGSN) to catalogue and standardize proper names for stars. The WGSN decided to attribute proper names to individual stars rather than entire multiple systems. It approved the name ''Rotanev'' for the component Beta Delphini A on 12 September 2016 and it is now so included in the List of IAU-approved Star Names. In Chinese, (), meaning '' Good Gourd'', refers to an asterism consisting of Beta Delphini, Alpha Delphini, Gamma² Delphini,

Delta Delphini Delta Delphini, Latinized from δ Delphini, is a binary star in the northern constellation of Delphinus. It is visible to the naked eye with an apparent visual magnitude of 4.43. Based upon an annual parallax shift of 14.61 mas as ...

, and

Zeta Delphini Zeta Delphini (ζ Delphini) is a star in the constellation of Delphinus. With an apparent magnitude of about 4.6, it is faintly visible to the naked eye. Parallax measurements of the system made by the Hipparcos spacecraft put it at a di ...

. ''中國星座神話'', written by 陳久金. Published by 台灣書房出版有限公司, 2005, .

Properties

Beta Delphini was found to be a

system in 1873 by the American astronomer S. W. Burnham. The system consists of a pair of F-type stars that

orbit In celestial mechanics, an orbit is the curved trajectory of an object such as the trajectory of a planet around a star, or of a natural satellite around a planet, or of an artificial satellite around an object or position in space such a ...

each other with a period of 26.66 years and an eccentricity of 0.36. The plane of the orbit is

inclined Incline, inclined, inclining, or inclination may refer to: *Grade (slope), the tilt, steepness, or angle from horizontal of a topographic feature (hillside, meadow, etc.) or constructed element (road, railway, field, etc.) *Slope, the tilt, steepn ...

by an angle of 61° to the line of sight from the

Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's surf ...

. The two stars have an angular separation of about 0.44

arcsecond A minute of arc, arcminute (arcmin), arc minute, or minute arc, denoted by the symbol , is a unit of angular measurement equal to of one degree. Since one degree is of a turn (or complete rotation), one minute of arc is of a turn. The na ...

s, making them a challenge to resolve with a telescope. The larger member of the pair is a

giant star A giant star is a star with substantially larger radius and luminosity than a main-sequence (or ''dwarf'') star of the same surface temperature.Giant star, entry in ''Astronomy Encyclopedia'', ed. Patrick Moore, New York: Oxford University Press ...

with 1.75 times the

mass Mass is an intrinsic property of a body. It was traditionally believed to be related to the quantity of matter in a physical body, until the discovery of the atom and particle physics. It was found that different atoms and different element ...

and 24 times the

luminosity of the Sun The solar luminosity (), is a unit of radiant flux ( power emitted in the form of photons) conventionally used by astronomers to measure the luminosity of stars, galaxies and other celestial objects in terms of the output of the Sun. One nomin ...

, while the secondary component is a subgiant star that has 1.47 times the Sun's mass and around 8 times the Sun's luminosity. The system is around 1.8 billion years old.

References

External links

* {{DEFAULTSORT:Beta Delphini Delphinus (constellation) F-type subgiants F-type giants Binary stars Delphini, Beta Delphini, 06 196524 101769 Rotanev BD+14 4369 7882

Nomenclature

Properties

See also

References

External links