NATO Advanced Study Institute Planets outside the Solar System

SCIENTIFIC OBJECTIVES

The theoretical problem of the formation of the Solar System, and hence of other planetary systems, was tackled only during the 18th century, while the first observational attempts for a detection started less than one hundred years ago.

Direct observation of an extra-solar planetary system is an extraordinarily difficult problem: extra-solar planets are at huge distances (compared with the planets of our own Solar System), are incredibly faint and, moreover are overwhelmed by the bright light of their own stars. With virtually no observational insight to test their models, theoretical astrophysicists have remained for decades in a difficult position to make substantial progress.

Yet, the field of stellar formation has provided since the 1980s both theoretical and observational evidences for the formation of disks around stars in their making, and debris materials orbiting the very young stellar systems. It was tempting to consider that these left-overs might indeed agglomerate into planetary systems more or less similar to ours.

Then came (at last!) observational evidences for planets outside the Solar System. Hence, this was considered as the answer to a long standing conjecture, even if the physical nature of these planets was completely unexpected. It is nevertheless a real break-through, since from now on the interplay between theory and observations can booster the development of a new, and presumably very important, field of Astrophysics and Planetary Sciences.

As expressed in the title of the ASI, it is the emergence of this interplay mechanism that we would like to emphasize in this School.

Although very fresh, the observational data obtained to date have already triggered completely new models of formation and evolution, e.g. the possible migration of the 'hot-Jupiters' like the companion of 51 Peg from their believed birth-place to their actual position more than 100 times closer to their star.

On the other hand, new projects for detection and observation of extra-solar planets are springing. They rely either on indirect methods (where it is the influence of the planet on its star which is measured) or on direct methods (where the emission from the planet is actually detected). While ground-based surveys are already entering the operational phase, plans are presently discussed at space agencies to define and build the future generation of space missions, able not only to detect hundredths of new systems, but also aiming to start the characterization of these new planets through spectroscopy.

But of course the field of extra-solar planets does not pertain only to Planetary Sciences and Astrophysics. The question of the existence of other forms of life in the Universe is in the perspective of the current astronomical efforts. Although this point is still speculative, it will certainly play a role in the future orientations of the whole field of exo-planets research. This is why we propose to conclude the Advanced Study Institute on this topic.

In the same spirit, we wish to bracket the central program of specialized lectures with two seminars discussing these issues from the point of views of Science History and Philosophy.

The program is this ASI deals with topics from different fields (planetary system formation and evolution, ground and space-based advanced technology, exo-biology, philosophy,...). Therefore, we expect to attract through this trans-disciplinary approach students with various backgrounds. An exciting and fruitful output should emerge from this situation.

SCIENTIFIC ADVISORY COMMITTEE

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