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FROM THE SOLAR SYSTEM TO THE DISTANT UNIVERSE

MICHEL BLANC ABSTRACT Président de la section The Universe exhibits extreme conditions of temperature, density, radiation and gravitational JAMES LEQUEUX fields. Consequently, astronomy is strongly relevant Rapporteur to physics, chemistry and biology, aside its cultural and philosophical interest. Annie Baglin Research in astronomy has common features Jean-Paul Baluteau with geophysics: experiments are impossible, and Slimane Bensammar progresses can only come from a confrontation of models and theories to observations. Astronomical Alain Blanchard discoveries are particularly unpredictable, but have Jacques Colin proven to be strongly dependent on new instru- mentation. Like nuclear and particle physics, astro- Roger Ferlet nomy requires very large equipments, together with Marie-Claire Gazeau more modest facilities for long-term programs. The recent spectacular discoveries of extremely distant Maryvonne Gerin-Laslier galaxies and of planets around nearby stars were Georges Helmer done respectively with very large optical and radio on the Earth and in space, and with Jean-Pierre Lemonnier small instruments. Astronomy also involves service Michelle Loulergue observing for the general community, for example for accurate time keeping or for monitoring the François Pajot activity of the Sun. Guy Pelletier In , observational cosmology is already François-Xavier Schmider mature but theoretical cosmology is a relatively Guy Serra recent domain, showing rapid development. Extragalactic astronomy is also growing fast. The Guy Simon study of interstellar matter and star formation has Laurent Vigroux been a strong point for many years and is very

1 CNRS - RAPPORT DE CONJONCTURE 1996 active. Stellar and astronomy are in a phase of While observing the solar system with all these renewal. Solar-system astronomy has developed facilities, and also the space environment of the enormously and France is now a leader in this field. Earth with ground-based and space instruments in France is also a leader in the old field of astrometry cooperation with other countries (EISCAT, SUPER- and time measurement, for which the techniques DARN, soon the set of four satellites CLUSTER of have experienced considerable changes recently, for ESA, etc.), french astronomers also take a very example with the HIPPARCOS astrometry satellite. active part in various missions of solar-system exploration: CASSINI to Saturn and its satellite Most of astronomical research is based on Titan, later ROSETTA to a comet, both built by ESA. observation of celestial objects at many different wavelengths. France has access to excellent instru- Finally, France and Italy are building together mentation covering the whole electromagnetic a large detector of gravitational waves, VIRGO. spectrum. -ray astronomy from space is very developed, with the experiment SIGMA on the rus- Of course, as any healthy community, the sian satellite GRANAT, and soon the INTEGRAL french astronomers have longer-term projects and project of the European Space Agency (ESA). On plans, but they are outside the scope of the present the ground, CAT is just starting operation and there report. is another project, CELESTE. X-ray astronomy has not been very active recently in France, but this will The main problems of french astronomy are to change soon with the participation to the satellite organize in data bases the large amounts of infor- XMM of ESA. In the ultraviolet, the visible and the mation coming from all these instruments, to main- near-infrared, french astronomers are regular users tain the adequacy of the means for processing their of the Hubble Space and share with data, and also to have enough computing facilities other countries large ground-based facilities: the for maintaining an activity in theory and modelling Canadian-France-Hawaii telescope, THEMIS for appropriate to the pace at which the observations solar research, and the instruments of the European are gathered. Astronomers have good collabora- Southern Observatory (ESO). France takes a very tions with physicists, chemists and geophysicists, active part in the development of techniques allo- but should tighten the present ties. They should wing to reach a very high angular resolution: adap- also devote more effort in answering adequately the tive optics and interferometry, which are both being considerable public demand for astronomical implemented on the Very Large Telescope of ESO knowledge. Finally, while astronomy is already well presently under construction in Chile. France has organized on a world-wide basis, a special effort also been active in building the instrumentation of should be devoted in building a genuine european the mid- and far-infrared satellite ISO of ESA, and is astronomical community, based of course on the presently gathering the remarkable scientific out- existing but independent european societies like come of this mission. It also participates in various ESA, ESO, IRAM and EISCAT. space projects in the far-infrared and sub-millime- ter domains, in particular the satellites and A general discussion on the present and future FIRST of ESA. Radioastronomy is also very develo- of french astronomy will take place in a national ped, to a large part thanks to the french involve- colloquium to be held in Spring 1998. ment in the Institut de Radio Astronomie Millimetrique (IRAM).

Résumé en anglais établi par M. Blanc et J. Lequeux. Contact : [email protected]

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