Abstract. We present evolutionary models for cool brown dwarfs and extra-solar giant planets. The models reproduce the main trends of observed methane dwarfs in near-IR color-magnitude diagrams. We also present evolutionary models for irradiated planets, coupling for the first time irradiated atmosphere profiles and inner structures. We focus on HD 209458-like systems and show that irradiation effects can substantially affect the radius of sub-jovian mass giant planets. Irradiation effects, however, cannot alone explain the large observed radius of HD 209458b. Adopting assumptions which optimise irradiation effects and taking into account the extension of the outer atmospheric layers, we still find ∼20% discrepancy between observed and theoretical radii. An extra source of energy seems to be required to explain the observed value of the first transit planet.

Direct imaging of exoplanetary systems is a powerful technique that can reveal Jupiter-like planets in wide orbits, can enable detailed characterization of planetary atmospheres, and is a key step toward imaging Earth-like planets. Imaging detections are challenging because of the combined effect of small angular separation and large luminosity contrast between a planet and its host star. High-contrast observations with the Keck and Gemini telescopes have revealed three planets orbiting the star HR 8799, with projected separations of 24, 38, and 68 astronomical units. Multi-epoch data show counter clockwise orbital motion for all three imaged planets. The low luminosity of the companions and the estimated age of the system imply planetary masses between 5 and 13 times that of Jupiter. This system resembles a scaled-up version of the outer portion of our solar system.

Aims. We present a new library of high-resolution synthetic spectra based on the stellar atmosphere code PHOENIX that can be used for a wide range of applications of spectral analysis and stellar parameter synthesis. Methods. The spherical mode of PHOENIX was used to create model atmospheres and to derive detailed synthetic stellar spectra from them. We present a new self-consistent way of describing micro-turbulence for our model atmospheres. Results. The synthetic spectra cover the wavelength range from 500 Å to 5.5 μm with resolutions of R = 500 000 in the optical and near IR, R = 100 000 in the IR and Δλ = 0.1 Å in the UV. The parameter space covers 2300 K ≤ T eff ≤ 12 000 K, 0.0 ≤ log g ≤ +6.0,The library is a work in progress and we expect to extend it up to T eff = 25 000 K.

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High-contrast near-infrared imaging of the nearby star HR 8799 has shown three giant planets. Such images were possible because of the wide orbits (>25 astronomical units, where 1 au is the Earth-Sun distance) and youth (<100 Myr) of the imaged planets, which are still hot and bright as they radiate away gravitational energy acquired during their formation. An important area of contention in the exoplanet community is whether outer planets (>10 au) more massive than Jupiter form by way of one-step gravitational instabilities or, rather, through a two-step process involving accretion of a core followed by accumulation of a massive outer envelope composed primarily of hydrogen and helium. Here we report the presence of a fourth planet, interior to and of about the same mass as the other three. The system, with this additional planet, represents a challenge for current planet formation models as none of them can explain the in situ formation of all four planets. With its four young giant planets and known cold/warm debris belts, the HR 8799 planetary system is a unique laboratory in which to study the formation and evolution of giant planets at wide (>10 au) separations.