To celebrate the centenial of General Relativity and simulataneously celebrate five years of the Gravitation Group at the University of Aveiro (Gr@v), established in the Fall 2010, Gr@v will organize a two days event, on 25-26 November 2015. This event will also mark the closing of the "Numerical Relativity and High Energy Physics" Marie Curie IRSES action, an international partnership which was coordinated by our group that ran over the period 2012-2015. Finally, the event will also be integrated in the IDPASC doctoral programme.
The chaotic rotation of Pluto's small moons has been explained by Gr@v researchers as a natural consequence of the gravitational dynamics in Pluto's system (A&A Letter).
C. Herdeiro was the guest interviewee of Porto Canal's "Mentes que Brilham". Watch and listen to the conversation with interviewer Cláudia Fonseca about black holes and some of the research work made at Gr@v in this area.
Abstract: Transiting exoplanets, that cross their stellar disk, are of special interest because their allow the determination of their bulk density by measuring both their radius and mass. Characterising transiting exoplanets is very important since it provides unique constraints to the theories of planet formation, migration and evolution. However, the planets that have been detected by the CoRoT and Kepler space missions transits relatively faint stars. The characterisation of the mass of those exoplanets is therefore challenging, especially in the low-mass regime. Those planets have a measured radius, but very poor constraints on their mass. In this seminar, I will present the objective of the search for transiting exoplanets and the methods to characterise them. Then, I will discuss the limitation of those techniques and finally, I will present the perspectives for the future exploration of the planet density's diversity.
Abstract: Coorbital bodies are observed around the Sun sharing their orbits with the planets, but also in some pairs of satellites around Saturn. The existence of coorbital planets around other stars has also been proposed. For close-in planets and satellites, the rotation slowly evolves until some kind of equilibrium is reached. When the orbits are nearly circular, the rotation period is believed to always end synchronous with the orbital period (as it happens for the Moon). Here we demonstrate that for coorbital bodies in quasi-circular orbits, stable non-synchronous rotation is possible for a wide range of mass ratios and body shapes. We further show that the rotation becomes chaotic when the natural rotational libration frequency has the same magnitude as the orbital libration frequency.
Abstract: The discovery of more than 900 planets orbiting other stars than our Sun makes this period very exciting. Our knowledge which was based on the Solar System has been challenged by new planetary systems which are very different from our system. Some of them are much more compact than the Solar System. Some planets are located extremely close-in from their star, within the orbital distance of Mercury, in a region where tidal effects are important. Understanding the structure of the known exoplanetary systems and the future ones requires to take into account the physics of tidal evolution.
I will talk about the dynamical and tidal evolution of planetary systems orbiting evolving brown dwarfs. Close-in planets orbiting brown dwarfs are very interesting to study because they are influenced by tides and they can be in the habitable zone: the region around a star where a planet with an atmosphere can have water on its surface. I will show that tides are important for these systems because it has an effect on the possible habitability of planets.
Abstract: Since long time ago that it is been argued about a possible connection between the planets orbital motions in the solar system and the cycles of the activity of the Sun. These discussions have been based, often, on presumed correlations between the position of the planets and the occurrence of the solar maximum/minimum, but with no real physical explanation. However, very recently, Abreu et al. (2012) proposed that the planets dynamics can have an influence in the solar tachocline (a thin layer separating the solar radiative and convective regions) and, by consequence, in the activity of the Sun. Following that, several articles have been published with pro and con arguments (cf. Cameron & Schüssler 2013) . Thus, the subject is becoming particularly interesting. This talk will give a review of the current status of the discussion.
Abstract: During the last couple of years Radial Velocity and Transit surveys gathered a wealth of information about the structure of extrasolar systems. We are now putting all the information together and starting to understand the implications of these results on our understanding of the formation of planets. In this talk we will review some of the most recent results, and use the questions that are left open for dynamicists as the starting point for discussion.
Abstract: Some of the most famous works of Henri Poincaré (1854-1912) have been motivated by the problem of the stability of the Solar System. Indeed, since its formulation by Newton, this problem has fascinated astronomers and mathematicians, searching to prove the stability of the Solar System. Poincaré demonstrated that the perturbative methods of the astronomers could not be used to provide an answer to the problem of stability on infinite time because the series that were used are in general divergent. At the same time he believed that the dissipative terms would be of larger importance than the conservative neglected terms, leading to a stable final state for the Solar System. In the following of the work of Poincaré, KAM theorems have provided new hopes for mathematicians to prove the stability of the Solar System. On the opposite, the recent numerical works on realistic models of the Solar System show that the system is unstable in the strong sense and that planetary collisions are possible within the lifetime of the Sun.
Our group coordinated the "Numerical Relativity and High Energy Physics" IRSES network (2012-2015). Here is a list of the global network meetings organized:
