18 Delphini b
18 Delphini b is an exoplanet candidates orbiting the yellow giant star 18 Delphini all 993 days. Because of its mass is assumed that it is a gas planet or brown dwarf.
Discovery
18 Delphini b was detected using the radial velocity method by a working group to Bun'ei Satō at the Okayama Astrophysical Observatory in Asakuchi. The discovery was published on 19 February 2008.
Web properties
The planet orbits its star at a distance of about 2.6 astronomical units and thus had the time of publication the furthest orbit of all the known extrasolar planets around older stars. In relation to the solar system would be the orbit between Mars and Jupiter. The orbit is at an eccentricity of 0.08 nearly circular.
Physical Properties
Due to the variability in the radial velocity of 18 Delphini the minimum mass of 18 Delphini b is derivable, it is about 10.3 times Jupiter's mass (ca. 3270 Earth masses ). Since the orbital inclination is unknown, the mass could also be significantly higher. Whether Delphini 18 b is really a planet, so can not yet be said with certainty. Its diameter is in any case probably less than that of Jupiter, so that 18 Delphini b is likely to have a very high density.
The power dissipation of 18 Delphini and the distance from its central star suggest a minimum surface temperature of 400 Kelvin ( 130 ° C) include, in all likelihood, the planet is still significantly warmer through their own energy -releasing processes. About the chemical composition is not known, probably are the most common elements in the universe, ie hydrogen and helium, as well as in the gas giant in our solar system, its main components. According to current models should Delphini 18 b have either a cloudless atmosphere, which appears deep blue due to Rayleigh scattering, or, if it is a little cooler, forming 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, pp. 539-550, arXiv: 0802.2590.