18 Delphini

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18 Delphini
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Delphinus
Right ascension 20h 58m 25.93s
Declination +10° 50' 21.43″
Apparent magnitude (V) 5.522
Absolute magnitude (V) 1.202
Distance 238.493 ly
(73.121 pc)
Spectral type G6III:
Other designations
Musica, BD+10° 4425, HD 199665, HIP 103527, HR 8030, GC 29266, SAO 106712
Database references

18 Delphini (abbreviated 18 Del), also named Musica,[1] is a yellow giant star of spectral type G6III situated approximately 238 light-years from Earth in the constellation of Delphinus. An extrasolar planet (designated 18 Delphini b, later named Arion) is believed to be orbiting the star.


18 Delphini is the star's Flamsteed designation. Following its discovery the planet was designated 18 Delphini b.[2]

In July 2014 the International Astronomical Union launched a process for giving proper names to certain exoplanets and their host stars.[3] The process involved public nomination and voting for the new names.[4] In December 2015, the IAU announced the winning names were Musica for this star and Arion for its planet.[5]

The winning names were those submitted by the Tokushima Prefectural Jonan High School Science Club of Japan. 'Musica' is Latin for 'music'. Arion was a genius of poetry and music in ancient Greece. According to legend, his life was saved at sea by dolphins after attracting their attention by the playing of his kithara [6] ('Delphinus' is Latin for 'dolphin').

In 2016, the IAU organized a Working Group on Star Names (WGSN)[7] to catalog and standardize proper names for stars. In its first bulletin of July 2016,[8] the WGSN explicitly recognized the names of exoplanets and their host stars approved by the Executive Committee Working Group Public Naming of Planets and Planetary Satellites, including the names of stars adopted during the 2015 NameExoWorlds campaign. This star is now so entered in the IAU Catalog of Star Names.[1]

Planetary system[edit]

On February 19, 2008, a 10.3 Jupiter mass extrasolar planet was found to be orbiting the star.[2]

The 18 Delphini planetary system[2]
(in order from star)
Mass Semimajor axis
Orbital period
Eccentricity Inclination Radius
b (Arion) >10.3 MJ 2.6 993.3 ± 3.2 0.08 ± 0.01


External links[edit]

Coordinates: Sky map 20h 58m 26s, +10° 50′ 21″