Since it began its survey of the
section of the sky dubbed the Kepler Deep Field in 2009, the Kepler Space Telescope has discovered 2321 probable planets around 1790 stars, and it is
thought that the vast majority of these probable planets will turn out to be
true planets. The star given the designation KOI 676 (Kepler Object of Interest
676) was identified as a probable planet-host in 2011. It is a K-type Orange
Dwarf Star, with 63%of the Sun’s mass, and an effective temperature of 4300K
(compared to 5778K for the Sun), and is thought to be about 350 million years
old.
In a paper published on the
online arXiv database at Cornell University Library on 13 March 2014, and
accepted for publication in the journal Astronomy & Astrophysics, Panagiotis Ioannidis and Jürgen Schmitt of the Hamburger Sternwarte at Universität Hamburg, Chrysa Avdellidou of the Centre for Astrophysics and Planetary Science at the School of Physical Sciences at The University of Kent, Canterbury, Carolina von Essen, also
of the Hamburger Sternwarte at Universität Hamburg, and Eric Algol of the
Department of Astronomy at the University of Washington, describe the discovery
of a planetary system about KOI 676.
With the conformation of planets
the system is renamed Kepler 210 (i.e. the 210th confirmed planetary
system in the Kepler study), and the Star becomes Kepler 210A (when naming
objects in other stellar systems stars are given upper case letters and planets
lower class letters). Two planets, calculated to be roughly Neptune-sized, were
detected making transits of the star on a regular basis, these are named Kepler
210b, which orbits the star once every 2.45 days, and Kepler 210c, which orbits
the star every 7.97 days.
These two planets appear to have
somewhat eccentric orbits (i.e. they have highly elliptical orbits and get
notably closer and further away from the star during each circuit about it),
which proved difficult to model based upon the available data about the mass
and orbits of the star and planets. Ionnidis et al. tried a variety of models in order to try to explain this,
and concluded that the most likely explanation was the presence of a third
planet, with a mass of between 30% and 60% that of Jupiter, orbiting the star
every 63 days, the gravity of which would perturb the other bodies in the way
observed.
This theoretical body is given
the designation KOI 676.03, retaining the system’s provisional designation due
to its theoretical, rather than
confirmed, status.
The suggested configuration of
the Kepler 210 system. The innermost planet is Kepler 210a, the outermost KOI
676.03. The arrow points towards Earth. Scale bars are in AU (Astronomical
Units); 1 AU is the average distance between the Earth and the Sun.
See also GJ 504b, a cold Jovian exoplanet in a wide orbit about a Sun-like star, Three giant exoplanets in very wide orbits around young stars, Kepler 63b; a giant planet in a polar orbit, A superjovian exoplanet directly imaged orbiting the A-class pre main-sequence star HD 95086 and
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