18 Delphini b

18 Delphini b (abbreviated 18 Del b), formally named Arion /əˈraɪən/,^[2] is an extrasolar planet approximately 245 light-years away in the constellation of Delphinus.^[3]

18 Delphini b / Arion

Radial velocity changes over time of 18 Delphini caused by the orbit of 18 Delphini b.
Discovery
Discovered by	Sato et al.[1]
Discovery site	Okayama Planet Search Program Japan
Discovery date	19 February 2008
Detection method	radial velocity
Orbital characteristics
Semi-major axis	2.476 AU (370,400,000 km)
Eccentricity	0.08 ± 0.01
Orbital period (sidereal)	993.3 ± 3.2 d 2.719 y
Time of periastron	2451672 ± 18
Argument of periastron	166.1 ± 6.5
Star	18 Delphini
Physical characteristics
Mass	9.207

The 993-day period planet orbits the Red clump star 18 Delphini 2.476 AU away every 2.719 years. It is a very massive and dense planet with a mass of 9.207 M_J, it was discovered on February 19, 2008, by Bun'ei Sato.^[4][1]

In July 2014, the International Astronomical Union launched NameExoWorlds, a process for giving proper names to certain exoplanets and their host stars.^[5] The process involved public nomination and voting for the new names.^[6] In December 2015, the IAU announced the name Arion for this planet.^[7] The winning name was submitted by the Tokushima Prefectural Jonan High School Science Club of Japan. 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^[8] ('Delphinus' is Latin for 'dolphin').

See also

• 41 Lyncis b
• Xi Aquilae b