UV Capabilities to Probe the Formation of Planetary Systems: From the ISM to Planets

Abstract

Planetary systems are angular momentum reservoirs generated during star formation. Solutions to three of the most important problems in contemporary astrophysics are needed to understand the entire process of planetary system formation:The physics of the ISM. Stars form from dense molecular clouds that contain ∼30% of the total interstellar medium (ISM) mass. The structure, properties and lifetimes of molecular clouds are determined by the overall dynamics and evolution of a very complex system -the ISM. Understanding the physics of the ISM is of prime importance not only for Galactic but also for extragalactic and cosmological studies. Most of the ISM volume (∼65%) is filled with diffuse gas at temperatures between 3000 and 300 000 K, representing about 50% of the ISM mass. ing star formation, the so-called accretion-outflow engine. Elementary physical considerations show that, to be efficient, the acceleration region for the outflows must be located close to the star (within 1 AU) where the gravitational field is strong. According to recent numerical simulations, this is also the region where terrestrial planets could form after 1 Myr. One should keep in mind that today the only evidence for life in the Universe comes from a planet located in this inner disk region (at 1 AU) from its parent star. The temperature of the accretion-outflow engine is between 3000 and 10 7 K. After 1 Myr, during the classical T Tauri stage, extinction is small and the engine becomes naked and can be observed at ultraviolet wavelengths. The physics of planet formation. Observations of volatiles released by dust, planetesimals and comets provide an extremely powerful tool for determining the relative abundances of the vaporizing species and for studying the photochemical and physical processes acting in the inner parts of young planetary systems. This region is illuminated by the strong UV radiation field produced by the star and the accretion-outflow engine. Absorption spectroscopy provides the most sensitive tool for determining the properties of the circumstellar gas as well as the characteristics of the atmospheres of the inner planets transiting the stellar disk. UV radiation also pumps the electronic transitions of the most abundant molecules (H 2 , CO, etc.) that are observed in the UV.Here we argue that access to the UV spectral range is essential for making progress in this field, since the resonance lines of the most abundant atoms and ions at temperatures between 3000 and 300 000 K, together with the electronic transitions of the most abundant molecules (H 2 , CO, OH, CS, Springer 34 Astrophys Space Sci (2006) 303:33-52 S 2 , CO + 2 , C 2 , O 2 , O 3 , etc.) are at UV wavelengths. A powerful UV-optical instrument would provide an efficient mean for measuring the abundance of ozone in the atmosphere of the thousands of transiting planets expected to be detected by the next space missions (GAIA, Corot, Kepler, etc.). Thus, a follow-up UV mission would be optimal for identifying Earth-like candidates.

Imaging and Characterization of Extrasolar Planets with the Next Generation of Space Telescopes

“…Most of the known planetary systems have been detected by the transit method and the observation of UV and optical absorption during transit is a very powerful diagnostic technique [30,31]. Important bio-markers absorb efficiently the stellar radiation at ultraviolet-optical wavelengths.…”

First high dynamic range and high resolution images of the sky obtained with a diffractive Fresnel array telescope

“…At longer distances, there is established scientific interest in the UV domain for the accretion disks around young stars and formation of exoplanetary systems [10,11,25]. These rotating reservoirs of gas and dust are the birthplaces of new planetary systems and UV radiation plays an important role in synthesizing the organic molecules necessary for the emergence of life.…”

Is Life an Unavoidable Consequence of the Formation of the Universe? Investigating the Formation of Bio-Precursors and the Signature of Earth-Like Living Forms

“…Detailed calculations have been carried out to evaluate the instrumentation needed to detect bio-tracers in Earth-like planets by the transit method concluding that collecting surfaces equivalent to a 10-20 m primary are required for these new generation of telescopes (Ehrenreich et al, 2006;Gómez de Castro et al, 2006;Arnold et al, 2014). The detection of the H I envelopes of Earth-like exoplanets may prove to be easier.…”