The mass of the star is only 0 42 ± 0 05 M  ⊙  (Anglada-Escude et

GJ 317   GJ 317 is a red dwarf of spectral type M3.5 located relatively close to the Sun, MEK162 purchase namely at a distance of 15.3 pc. The mass of the star is only 0.42 ± 0.05 M  ⊙  (Anglada-Escude et al. The existence of planet c with its orbital period of about 2700 days still requires confirmation. HD 108874   HD 108874 consists of a G5 dwarf and two giant planets. The central star with metallicity [Fe/H] = 0.14 has the same selleckchem mass of the Sun and its distance

from our star is 68.5 pc (Butler et al. 2003). Goździewski et al. (2006) have confirmed that two gas giants in this system are close to the 4:1 resonance. In addition, selleck kinase inhibitor similarly to the cases of the systems HR 8799, HD 82943, HD 128311 and HD 202206 (which will be discussed later in this section) in HD 108874 there is also a dusty debris disc (Dodson-Robinson et al. 2011). HD 102272   In this system the giant planets are close to the 4:1 resonance. HD 102272 a is a giant star of spectral type K0. Its effective temperature is 4908 ± 35 K, log(g) = 3.07 ± 0.12 and the metallicity is [Fe/H] = − 0.26 ± 0.08. The mass of the star is 1.9 ± 0.3 M  ⊙  (Niedzielski et al. 2009) and the radius R = 10.1 ± 4.6 R  ⊙  (Alonso et al. 2000).

Only one of the gas giants in this system is fully confirmed, namely the component b. The observational data are still not sufficient in order to demonstrate convincingly the existence of a second planet. The

assumption that the two planets are close to the 4:1 resonance would significantly improve the stability of the configuration, which would remain stable during 109 years of evolution. It is worth looking also at commensurabilities of order higher than three. Two systems might contain planets close to the 5:1 resonance: HD 17156 and HD 202206. HD 17156   HD 17156 a is a star of spectral type G0 (Fischer et al. 2007), around which there is a planet on a very eccentric orbit, namely e = 0.68 (Fischer et al. 2007; Barbieri et al. 2009). The host star has effective temperature equal to T eff = 6079 ± 80 K and metallicity [Fe/H] = 0.24 ± 0.05 (Fischer et al. 2007). The mass of the star is 1.275 ± 0.018 M  ⊙  and its radius 1.508 ± 0.021 R  ⊙  (Nutzman et al. 2011). The announcement of the discovery of a planet c close to the 5:1 resonance has Bacterial neuraminidase been reported in a paper which as for today is still unpublished (Short et al. 2008). HD 202206   HD 202206 a is a star with very high metallicity [Fe/H] = 0.37 ± 0.07. Its spectral type is G6V, the distance from the Sun is 46.3 pc and its effective temperature amounts to T eff = 5765 K. The mass of the star is 1.044  M  ⊙  (Sousa et al. 2008), its age is of about 5.6 ± 1.2 × 109 years (Udry et al. 2002) or 4.2 × 109 years (Saffe et al. 2005). Also in this system a debris disc has been discovered (Moro-Martin et al. 2010).

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