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Alpha Delphini (α Delphini, abbreviated Alpha Del, α Del) is a multiple star system in the constellation of
Delphinus Delphinus (Pronounced or ) is a small constellation in the Northern Celestial Hemisphere, close to the celestial equator. Its name is the Latin version for the Greek word for dolphin (). It is one of the 48 constellations listed by the 2nd c ...
. It consists of a triple star, designated Alpha Delphini A, together with five faint, probably
optical Optics is the branch of physics that studies the behaviour and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behaviour of visible, ultravio ...
companions, designated Alpha Delphini B, C, D, E and F. A's two components are themselves designated Alpha Delphini Aa (officially named Sualocin , the historical name for the entire system) and Ab.


Nomenclature

''α Delphini'' ( Latinised to ''Alpha Delphini'') is the system's Bayer designation. The designations of the six constituents as ''Alpha Delphini A'' to ''F'', and those of ''A's'' components - ''Alpha Delphini Aa'' and ''Ab'' - derive from the convention used by the Washington Multiplicity Catalog (WMC) for multiple star systems, 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, outreac ...
(IAU). The primary star's components Aa, Ab1, and Ab2 are also sometimes referred to as A, Ba, and Bb respectively, given that the outer pair have been resolved. The system bore an historical name, ''Sualocin'', 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 Pa ...
was the assistant to
Giuseppe Piazzi Giuseppe Piazzi ( , ; 16 July 1746 – 22 July 1826) was an Italian Catholic priest of the Theatine order, mathematician, and astronomer. He established an observatory at Palermo, now the '' Osservatorio Astronomico di Palermo – Giuseppe S ...
, 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 star names. They have endured, the result of Cacciatore's little practical joke of naming the two stars after himself. In 2016, 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, outreac ...
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 proper names for stars for the international astronomical community. It operates under Division C – Education ...
(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 ''Sualocin'' for the component Alpha Delphini Aa on 12 September 2016 and it is now so included in the List of IAU-approved Star Names. In
Chinese Chinese can refer to: * Something related to China * Chinese people, people of Chinese nationality, citizenship, and/or ethnicity **''Zhonghua minzu'', the supra-ethnic concept of the Chinese nation ** List of ethnic groups in China, people of ...
, (), meaning '' Good Gourd'', refers to an asterism consisting of Alpha Delphini, Gamma2 Delphini, Delta Delphini, Beta Delphini and Zeta Delphini. Consequently, the
Chinese name Chinese names or Chinese personal names are names used by individuals from Greater China and other parts of the Chinese-speaking world throughout East and Southeast Asia (ESEA). In addition, many names used in Japan, Korea and Vietnam are ofte ...
for Alpha Delphini itself is (, en, the First Star of Good Gourd). In
Hindu astronomy Astronomy has long history in Indian subcontinent stretching from pre-historic to modern times. Some of the earliest roots of Indian astronomy can be dated to the period of Indus Valley civilisation or earlier. Astronomy later developed as a dis ...
, the star corresponded to one of the nakshatras named Dhanishta.


Properties

Alpha Delphini A is a spectroscopic binary star which has now been resolved using
speckle interferometry Speckle imaging describes a range of high-resolution astronomical imaging techniques based on the analysis of large numbers of short exposures that freeze the variation of atmospheric turbulence. They can be divided into the shift-and-add ("'' ...
. The components are separated by and have a 17-year
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 as ...
. Alpha Delphini Aa has a
spectral type In astronomy, stellar classification is the classification of stars based on their spectral characteristics. Electromagnetic radiation from the star is analyzed by splitting it with a prism or diffraction grating into a spectrum exhibiting the ...
of B9IV. it is a
subgiant A subgiant is a star that is brighter than a normal main-sequence star of the same spectral class, but not as bright as giant stars. The term subgiant is applied both to a particular spectral luminosity class and to a stage in the evolution ...
that has begun to evolve away from the main sequence, is about 3.8 times as massive as the sun and about twice as hot. The spectral type of the secondary star cannot be determined as it is too close and too faint compared to the primary, but it has been shown to itself be a binary star with an orbit of 30 days. Spectral lines showing 30-day radial velocity changes are likely to belong to the faintest component, expected from its mass to be an F-type star. Then the more massive star of the inner pair is likely to be an A-type dwarf, possibly not detected in the spectral because rapid rotation blurs its absorption lines. The five faint companions have
visual magnitude Apparent magnitude () is a measure of the brightness of a star or other astronomical object observed from Earth. An object's apparent magnitude depends on its intrinsic luminosity, its distance from Earth, and any extinction of the object's lig ...
s around 11th to 13th magnitude and separations of 35" to 72". They all show motion relative to Alpha Delphini A, and have much smaller parallaxes.


References

{{DEFAULTSORT:Alpha Delphini Delphini, Alpha Delphini, 09 Delphinus (constellation) Binary stars 7 B-type subgiants Sualocin 101958 7906 BD+15 4222 196867