Entrada Departamento Notícias Michel Mayor, cientista que descobriu o primeiro exoplaneta em 1995 apresenta palestra na FCUP

Michel Mayor, cientista que descobriu o primeiro exoplaneta em 1995 apresenta palestra na FCUP

O Professor Michel Mayor, Professor Emérito da Universidade de Genebra, Suiça, cientista que descobriu o primeiro exoplaneta em 1995, apresentará no dia 6 de Novembro às 15:00 no Auditório Ferreira da Silva uma palestra sobre a sua descoberta e os mais recentes desenvolvimentos na detecção dos exoplanetas.


The plurality of worlds in the cosmos:

An old dream of humanity. A modern reality of astrophysics.

Michel Mayor

Emeritus professor

University of Geneva


Already during the antiquity, Greek philosophers discussed the question of the "plurality of worlds" in the universe as well as the possibility of the "plurality of inhabited worlds". More than 20 centuries ago, Epicurus expressed his deep feeling that other worlds should exist in infinite numbers in the universe.

Across the last two millennia, that question remained a philosophical discussion. More recently, the supposed existence of other worlds with living species has been at the root of numerous fictions published during the 20th century. However, it is interesting to notice that prior to 1940, astronomers were giving extremely low estimates about the number of planetary systems existing in the Milky Way Galaxy: something between zero and a few very rare systems.  This past estimation is quite fascinating as the number of stars in our galaxy is larger than one hundred billions. In the 40's, the old paradigm of planetary formation drastically changed and immediately the estimated number of possible planetary systems in the Milky Way jumped to billions.

The most accepted mechanism of planetary formation was proposed by Otto Schmidt and Victor Safronov about 60 years ago. Dust coalescence in the disc leads to a slow formation of planetesimals, who growing in mass finally create low mass rocky planets.  In the regions of the disc distant enough from the star, the presence of ice particles makes the formation process more efficient and creates what will eventually become planetary cores. When one of those proto-planetary cores achieves a mass equivalent to about 10 times the mass of the Earth, it causes a fast-gravitational collapse of gas in the surrounding accretion disc which completes the formation of a gaseous giant planet similar to Jupiter in our solar system.

In 1994, we initiated a systematic search at the Haute-Provence Observatory to attempt detecting potential very low mass companions orbiting solar-type stars. Only after a few months, the first hint of a periodic variation in the velocity of one of the measured stars was obtained, but ... with a period as short as 4.2 days and gave an estimated mass close to half the mass of Jupiter. A Jovian planet on such a short period, orbiting its solar-type host star at a distance of only 5% of the separation between the Sun and Earth appeared to be in serious contradiction with the predicted core-collapse scenario.

Since that first discovery, the number of detected planets has increased continuously. Today more than 4000 exoplanets have well characterised orbits. During the last 23 years, not only did we reach impressive numbers of new planets but thanks to the design of more stable and sensitive spectrographs as well as the development of new techniques it was possible to extend the search to the domain of much less massive planets.

All these discoveries have revealed the amazing diversity of planetary systems. The galore of data acquired in the last 23 years contributes to understand the physics of planetary system formation and in particular of our own solar system.

However, we cannot ignore the most ambitious long-term challenge: the search for life in another place in the universe.

Is it realistic to detect life signatures on extra-solar planets? Do we have the instrumental capabilities to detect and study planets as small as earth analogues? What are the instruments in development and their scientific goals?

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