Pathways to Habitability: From Disks to Stars, Planets to Life

Stars and planets form as the end products of a complex chain of mechanisms starting in the galactic interstellar medium. In the course of molecular cloud contraction and collapse, the initial conditions are set for all further evolution of the forming star and its planetary system. The ensuing processes of disk formation and evolution, growth of planets and evolution of their atmospheres lead to the large range of planetary environments witnessed in our own solar system but becoming evident also in the largely growing sample of extrasolar planetary systems. Conditions for habitability may be met on some planets, allowing formation of life to proceed. The forming and evolving stars themselves play an overwhelming role in controlling the evolution of their environments. Specifically, short-wavelength radiation (UV, EUV, X-rays), stellar ionized winds, and high-energy particles have been recognized to play a fundamental role in processing circumstellar material (e.g., ionization, heating, and chemical processing of protoplanetary disk surfaces); at later stages when planets have formed, the same agents are responsible for driving chemical and physical processes in planetary magnetospheres, ionospheres, and upper atmospheres, including their erosion. How regions are established that potentially become habitable places in the evolving star-disk-planet systems is presently rather poorly understood. Apart from the direct starlight allowing for mild climates and liquid water on a planetary surface, many further conditions must be fulfilled and be kept within limits during the violent early years of a star`s life. In particular, high levels of strongly varying X-ray output, strong stellar winds, and stellar mass ejections not known on the present-day Sun define environments very different from any in our present-day solar system. To address questions on the formation of habitable environments in young stellar/planetary systems, we are proposing a multi-disciplinary national research network capitalizing on expertise available in different research centers in Austria. This network program will study feedback between the forming and evolving star and its protoplanetary disk and planetary system environment from the stage of star formation to young, fully formed and evolving planetary systems. We will specifically address the evolution of protoplanetary disk material under the influence of the magnetically active central star, the radiation, wind, and high-energy particle conditions around young stars themselves, relating them to episodes of extreme solar activity, the processing, evolution and erosion of upper planetary atmospheres and magnetospheres in extreme conditions prevailing in young stellar systems, and the evolution of habitable environments in multiple stellar systems. Our principal goal will be to understand the formation and early evolution of habitable environments in young, active stellar surroundings in which high-energy processes and radiation prevail. These studies will reach significantly beyond any presently being conducted, and will strongly link to future observing opportunities with instruments such as the James Webb Space Telescope, ALMA, PLATO and others.