Arion (exoplanet)

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Arion ( Flamsteed designation 18 Delphini b) is an exoplanet candidate that orbits the yellow giant star Musica every 993 days . Due to its mass , it is believed to be a gas planet or brown dwarf .

discovery

Arion was detected using the radial velocity method by a group led by Bun'ei Satō at the Okayama Astrophysical Observatory in Asakuchi . The discovery was published on February 19, 2008.

Track properties

The planet orbits its star at a distance of approx. 2.6 astronomical units and thus had the furthest orbit of all known extrasolar planets around older stars at the time of publication. In relation to the solar system, the orbit would be between that of Mars and Jupiter. The orbit is nearly circular with an eccentricity of 0.08.

Physical Properties

The minimum mass of Arion can be derived from the deviations in the radial velocity of Musica, it is around 10.3 masses of Jupiter (approx. 3270 earth masses ). Since the orbit inclination is unknown, the mass could also be significantly higher. So far it cannot be said with certainty whether Arion is really a planet. In any case, its diameter is probably less than that of Jupiter, so that Arion should have a very high density.

The energy radiation of Arion and the distance to its central star suggest a minimum surface temperature of 400  Kelvin (around 130 ° C), in all probability the planet is still significantly warmer due to its own energy-releasing processes. Nothing is known about the chemical composition, probably the most common elements in the universe, i.e. hydrogen and helium , as with the gas giants in the solar system, are its main components. According to current models, Arion should either have a cloudless atmosphere that appears deep blue due to Rayleigh scattering , or, if it is slightly cooler, form white water clouds.

swell

  • Bun'ei Satō et al .: Planetary Companions around Three Intermediate-Mass G and K Giants: 18 Del, xi Aql, and HD 81688 . In: Publications of the Astronomical Society of Japan . Vol. 60, No. 3 , February 19, 2008, p. 539-550 , arxiv : 0802.2590 .

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