HD 202206

Starbox begin
name = HD 202206 Starbox observe
epoch = J2000.0
constell = Capricornus
ra = RA|21|14|57.79
dec = DEC|-20|47|20.1
appmag_v = +8.08 Starbox character
class = G6V
b-v = 0.714
u-b = ?
variable = none Starbox astrometry
radial_v = ?
prop_mo_ra = -38.23
prop_mo_dec = -119.77
parallax = 21.58
p_error = 1.14
dist_ly = 151.14
dist_pc = 46.3
absmag_v = +4.75 Starbox detail
age = (5.6 ± 1.2) × 10⁹
metal = 234%
mass = 1.15
radius = 1.02
rotation = ?
luminosity = 1.07
temperature = 5765 ± 40 Starbox catalog
names = HIP 104903 Starbox reference
Simbad = HD+202206

HD 202206 is a yellow dwarf star approximately 151 light-years away in the constellation Capricornus. The star is orbited by two companions with substellar masses in a near-resonant configuration.

Distance, age and metallicity

Measurements by the Hipparcos astrometric satellite give a parallax of 21.58 milliarcseconds, which corresponds to a distance of 46.3 parsecs [cite web|url=http://vizier.u-strasbg.fr/viz-bin/VizieR-S?HIP%20104903|work=The Hipparcos and Tycho Catalogues|publisher=ESA|year=1997|title=HIP 104903|accessyear=2006|accessmonthday=26 June] . It is similar in mass, radius, and luminosity to the Sun, though estimated to be older at around 5.6 Gyr oldcite journal|url=http://www.edpsciences.org/articles/aa/abs/2002/28/aa2416/aa2416.html|author=Udry, S. et al.|title=The CORALIE survey for southern extra-solar planets VIII. The very low-mass companions of HD 141937, HD 162020, HD 168443, HD 202206: Brown dwarfs or "superplanets"?|journal=Astronomy and Astrophysics|volume=390|year=2002|pages=267 – 279|doi=10.1051/0004-6361:20020685|format=abstract] . It is also more metal-rich than our Sun based on the amount of iron relative to hydrogen.

Planetary system

In 2002, analysis of radial velocity measurements of the star revealed the existence of a substellar companion (designated HD 202206 b) with at least 17 times the mass of Jupiter around the star in an eccentric orbit with a period of around 256 days. This mass exceeds the 13 Jupiter mass limit above which an object can undergo deuterium fusion in its core, which some take to be the dividing line between planets and brown dwarfs, a definition which is supported by the IAU. [cite web|url=http://www.dtm.ciw.edu/boss/definition.html|title=Definition of a "Planet"|publisher=Working Group on Extrasolar Planets (WGESP) of the International Astronomical Union|accessdate=2008-10-04] However, some authors have suggested that the core accretion process (the traditional model for planet formation) can form objects above this limit, up to around 25-30 Jupiter masses. [cite arXiv|eprint=0710.5667|class=astro-ph|title=Giant Planet Formation by Core Accretion|version=v1|author=Mordasini, C. "et al."|year=2007|accessdate=2008-10-04] The classification of HD 202206 b as a brown dwarf or "superplanet" is currently unclear.

Even after HD 202206 b was accounted for, the star still showed a drift in the radial velocity measurements, indicating another companion in a longer-period orbit. In 2004 after further observations, the parameters of a companion was announced [cite journal|url=http://www.edpsciences.org/articles/aa/abs/2005/35/aa2376-04/aa2376-04.html|author=Correia, A. et al.|title=The CORALIE survey for southern extra-solar planets. XIII. A pair of planets around HD202206 or a circumbinary planet?|journal=Astronomy and Astrophysics|volume=440|year=2005|pages=751–758|doi=10.1051/0004-6361:20042376|format=abstract] . This companion is about Jupiter's size, has a planetary mass, at least 2.44 times that of Jupiter, and has an eccentric orbit taking around 1384 days to complete. The planet is located in a 5:1 orbital resonance with the brown dwarf.

The formation history of this planetary system is interesting: depending on the method of formation of the inner companion, the system can either be regarded as consisting of a superplanet and a planet, or alternatively a planet revolving in a circumbinary orbit.

PlanetboxOrbit
exoplanet = b
mass = >17.4
period = 255.87 ± 0.06
semimajor = 0.83
eccentricity = 0.435 ± 0.001PlanetboxOrbit
exoplanet = c
mass = >2.44
period = 1383.4 ± 18.4
semimajor = 2.55
eccentricity = 0.267 ± 0.021

See also

* PSR B1620-26

References

External links

* [http://simbad.u-strasbg.fr/sim-id.pl?Ident=HD+202206 HD 202206] on " [http://simbad.u-strasbg.fr/simbad/ SIMBAD] "
* [http://exoplanet.eu/star.php?st=HD+202206 HD 202206] on " [http://exoplanet.eu/index.php Extrasolar Planets Encyclopaedia] "
* [http://www.lpl.arizona.edu/~rory/research/xsp/dynamics/ Extrasolar Planet Interactions] by Rory Barnes & Richard Greenberg, Lunar and Planetary Lab, University of Arizona