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Since the discovery of the first extrasolar planet more than twenty years ago, we have discovered nearly four thousand planets orbiting stars other than the Sun. Current observational instruments (on board the Hubble Space Telescope,…
Radio observations of ultracool dwarfs, objects comprising brown dwarfs and the very lowest mass stars, have mainly focused on analyzing their light-curve and spectral energy distributions providing valuable insights into their magnetic…
Exoplanets are now being discovered in profusion. However, to understand their character requires spectral models and data. These elements of remote sensing can yield temperatures, compositions, and even weather patterns, but only if…
Hurricanes are one of the most extreme storm systems that occur on Earth, characterized by strong rainfall and fast winds. The terrestrial exoplanets that will be characterized with future infrared space telescopes orbit M dwarf stars. As a…
Direct measurements of the spectra of extrasolar giant planets are the keys to determining their physical and chemical nature. The goal of theory is to provide the tools and context with which such data are understood. It is only by putting…
Interest among astronomers in the detection of extra-solar planets is accelerating with the growing realization that it may soon be technically feasible. The ongoing renaissance in telescope construction and the anticipated launches of new…
Planets with non-zero obliquity and/or orbital eccentricity experience seasonal variations of stellar irradiation at local latitudes. The extent of the atmospheric response can be crudely estimated by the ratio between the orbital timescale…
Close-in gas giants are expected to have a strong magnetic field of $\sim 10-100$G. Magnetic fields in extrasolar giant planets are detectable by future radio observations in $\gtrsim 10$MHz and the spectropolarimetry of atomic lines. In…
In order to understand the atmospheres as well as the formation mechanism of giant planets formed outside our solar system, the next decade will require an investment in studies of isolated young brown dwarfs. In this white paper we…
Exoplanets in extremely close-in orbits are immersed in a local interplanetary medium (i.e., the stellar wind) much denser than the local conditions encountered around the solar system planets. The environment surrounding these exoplanets…
An attempt is made to guess the overall cosmic abundance of `metals' and the contribution made by the energy released in their production to the total intensity of extragalactic background light (EBL). With a comparable or somewhat larger…
The majority of searches for radio emission from exoplanets have to date focused on short period planets, i.e., the so-called hot Jupiter type planets. However, these planets are likely to be tidally locked to their host stars and may not…
Clouds are ubiquitous in extrasolar planet atmospheres and are critical to our understanding of planetary climate and chemistry. They also represent one of the greater challenges to overcome when trying to interpret transit transmission…
What kind of environment may exist on terrestrial planets around other stars? In spite of the lack of direct observations, it may not be premature to speculate on exoplanetary climates, for instance to optimize future telescopic…
We investigate a population of transiting planets that receive relatively modest stellar insolation, indicating equilibrium temperatures $< 1000$ K, and for which the heating mechanism that inflates hot Jupiters does not appear to be…
Exoplanets orbiting M dwarf stars are a prime target in the search for life in the Universe. M dwarf stars are active, with powerful flares that could adversely impact prospects for life, though there are counter-arguments. Here, we turn…
The lowest-mass stars, brown dwarfs and extrasolar planets present challenges and opportunities for understanding dynamics and cloud formation processes in low-temperature atmospheres. For brown dwarfs, the formation, variation and rapid…
Atmospheric compositions for rocky exoplanets will depend strongly on the bulk planetary composition and the orbital position of the planet. Non-traditional gases may be present in the atmospheres of exceptionally hot planets. Atmospheres…
Electron-degenerate, pressure-ionized hydrogen (usually referred to as metallic hydrogen) is the principal constituent of brown dwarfs, the long-sought objects which lie in the mass range between the lowest-mass stars (about eighty times…
We present a time-dependent radiative model for the atmosphere of extrasolar planets that takes into account the eccentricity of their orbit. In addition to the modulation of stellar irradiation by the varying planet-star distance, the…