On the equilibrium rotation of Earth-like extra-solar planets

The equilibrium rotation of tidally evolved "Earth-like" extra-solar planets is often assumed to be synchronous with their orbital mean motion. The same assumption persisted for Mercury and Venus until radar observations revealed their true spin rates. As many of these planets follow eccentric orbits and are believed to host dense atmospheres, we expect the equilibrium rotation to differ from the synchronous motion. Here we provide a general description of the allowed final equilibrium rotation states of these planets, and apply this to already discovered cases in which the mass is lower than twelve Earth-masses. At low obliquity and moderate eccentricity, it is shown that there are at most four distinct equilibrium possibilities, one of which can be retrograde. Because most presently known "Earth-like" planets present eccentric orbits, their equilibrium rotation is unlikely to be synchronous.Comment: 4 pages, 2 figures. accepted for publication in Astronomy and Astrophysics. to be published in Astronomy and Astrophysic

HD60532, a planetary system in a 3:1 mean motion resonance

In a recent paper it was reported a planetary system around the star HD60532, composed by two giant planets in a possible 3:1 mean motion resonance, that should be confirmed within the next decade. Here we show that the analysis of the global dynamics of the system allows to confirm this resonance. The present best fit to data already corresponds to this resonant configuration and the system is stable for at least 5Gry. The 3:1 resonance is so robust that stability is still possible for a wide variety of orbital parameters around the best fit solution and also if the inclination of the system orbital plane with respect to the plane of the sky is as small as 15 deg. Moreover, if the inclination is taken as a free parameter in the adjustment to the observations, we find an inclination ~ 20 deg, which corresponds to M_b =3.1 M_Jup and M_c = 7.4 M_Jup for the planetary companions.Comment: 4 Pages, 4 Figures, accepted by A&

Reconstruction of the Past Climate in Southern Portugal from Geothermal Data

The study of the past climate in the territory of mainland Portugal using geothermal data started in 1996. From an initial set of about 90 temperature logs obtained Portugal, eight were chosen as good for estimating ground surface temperature (GST) in the past. The main results from the analysis of the collected geothermal data show, on average, that there has been an increase of the atmosphere mean surface temperature of about 1 K since the middle of the nineteenth century. This conclusion agrees with the results obtained from the analysis of air temperature records that were obtained in the Lisbon weather station since 1856. With the objective of improving the reconstruction of GST history in Portugal one of the eight wells (the TGQC-1 well) was cased and is being used for repeated temperature logging since 1997. The results of the temperature measurements repetition indicate that the warming trend continues to the present day, accelerating in the last 10 to 15 years. Since 2005 a geothermal climate change observatory was installed in the TGQC-1 well to study the air-ground coupling

On the possibility of using geothermal data for paleoclimate studies in Antarctica: the experience from Portugal

The study of the climate in the past and the climate change in mainland Portugal using geothermal data has started in 1996. Reconstruction of ground surface temperature (GST) history from temperature logs measured in a 200 m deep borehole located 5 km away from the town of Évora in Portugal, indicates a warming of 1K since the second half of the nineteenth century to the middle of the 90s of the twentieth century, increasing considerably in the last 10 years. Results of the reconstruction (based on a functional space inversion – FSI – method) are compared with air temperatures recorded at the Lisbon meteorological station since 1856. The air temperature time series display a warming trend with the amplitude about 1K for the same period. The coupling of the air and ground temperature changes and their downward propagation by heat conduction was confirmed by repeated logging in November 2003, 6.7 years after obtaining the first temperature log. The method can be used in paleoclimatic studies in Antarctica as well as in areas with permafrost

Anisotropic simplicial minisuperspace model

The computation of the simplicial minisuperspace wavefunction in the case of anisotropic universes with a scalar matter field predicts the existence of a large classical Lorentzian universe like our own at late timesComment: 19 pages, Latex, 6 figure