The physical properties of extra-solar planets

Abstract

Abstract. Tremendous progress in the science of extrasolar planets has been achieved since the discovery of a Jupiter orbiting the nearby Sun-like star 51 Pegasi in 1995. Theoretical models have now reached enough maturity to predict the characteristic properties of these new worlds, mass, radius, atmospheric signatures, and can be confronted with available observations. We review our current knowledge of the physical properties of exoplanets, internal structure and composition, atmospheric signatures, including expected biosignatures for exo-Earth planets, evolution, and the impact of tidal interaction and stellar irradiation on these properties for the short-period planets. We discuss the most recent theoretical achievements in the field and the still pending questions. We critically analyse the different solutions suggested to explain abnormally large radii of a significant fraction of transiting exoplanets. Special attention is devoted to the recently discovered transiting objects in the overlapping mass range between massive planets and low-mass brown dwarfs, stressing the ambiguous nature of these bodies, and we discuss the possible observable diagnostics to identify these two distinct populations. We also review our present understanding of planet formation and critically examine the different suggested formation mechanisms. We expect the present review to provide the basic theoretical background to capture the essential of the physics of exoplanet formation, structure and evolution, and the related observable signatures.

Evidence for a spectroscopic direct detection of reflected light from 51 Pegasi b

“…(1) and assumed that the planet-star flux ratio is given by the ratio of the amplitudes of the the detected planet and stellar CCFs. Note that the scatter of radii observed for hot-Jupiter planets of a given mass does not allow us to simply use the derived planetary mass to estimate a reliable value for the planetary radius (e.g., Baraffe et al 2010;Fortney & Nettelmann 2010).…”

Is tidal heating sufficient to explain bloated exoplanets? Consistent calculations accounting for finite initial eccentricity

“…As a result, tides raised in an eccentric planet can slow down its contraction (Bodenheimer et al 2001;Leconte et al 2009;Baraffe et al 2010) or even lead to a transitory phase of expansion (Miller et al 2009;). Correctly determining the tidal heating rate is thus a major issue in the evolution of short-period planets.…”

“…It is now well established that a large number of transiting giant exoplanets are more inflated than predicted by the standard cooling theory of irradiated gaseous giant planets (see Udry & Santos 2007;Baraffe et al 2010, for reviews). In order to quantify this effect we computed the radius predicted by our standard model, described in Sect.…”

“…In that case, an extra mechanism besides tidal heating must be invoked to solve this puzzling problem. Surface winds driven by the powerful incident stellar flux (Showman & Guillot 2002), converting kinetic energy to heat by dissipation within the tidal bulge and thus reaching deep enough layers to affect the planet's inner isentrope, or inefficient large-scale convection due to a composition gradient (Chabrier & Baraffe 2007) could be the other mechanisms to be considered with tidal dissipation to eventually lead to these large planet radii (see Baraffe et al 2010, for discussion).…”

Refined System Parameters and TTV Study of Transiting Exoplanetary System Hat-P-20

“…Through analysis of the long-term monitoring of TTV and/or TDV signals for transiting exoplanetary systems, even based on current ground-based measurements, terrestrial planets become easily detectable, even though they are difficult to detect by other detection methods (Agol et al 2005;Holman & Murray 2005). These fundamental parameters are indispensable for the study of planetary properties, such as the composition, structure, and even formation and evolution of the planetary system (Baraffe et al 2008(Baraffe et al , 2010Enoch et al 2012). Therefore, we have run a monitoring project since 2007 for several known transiting exoplanetary systems by using the 1 and 2.4 m telescopes of Yunnan Observatories (hereafter, YO-1 m and YO-2.4 m) and the 0.5 m telescope of Ho Koon Nature Education cum Astronomical Centre (hereafter, HKNEAC-0.5 m) in China, and published a series of observational results (Tan et al 2013;Wang et al 2013Wang et al , 2014Sun et al 2015).…”