Post Hipparcos Cosmic Candles

In May 1976, when one of us was temporarily associated with Stras bourg Observatory for lecturing on distance determination methods (Heck 1978), Pierre Lacroute - then in his last year as Director there - mod estly requested comments on a project he had been cherishing for quite a few years, and which he had been presenting to visitors and colleagues: an astrometric satellite. His persuasiveness and persistence won support from the scientific com munity, from the French space agency CNES and from the European Space Agency (ESA): the Hipparcos satellite was born. It was fitting that Lacroute lived long enough after his retirement to attend the launch of his brainchild in 1989 and to see it successfully operational. He knew however he would not enjoy the completion of this long and ambitious mission (he passed away on 14 January 1993, a few days before reaching the age of 87). In May 1997, in the prestigious setting of San Giorgio :Maggiore in Venice, ESA organized a symposium celebrating the presentation of the Hipparcos and Tycho catalogues. That conference signalled also the re lease of the first scientific results based at least partially on Hipparcos data. An impressive proceedings volume (Battrick 1997) of more than nine hundred pages, gathering together almost two hundred contributions, gave evidence of numerous studies in progress, in addition to papers starting to appear in the classical journals. The well-maintained ESA Hipparcos web site (http://astro. estec. esa.

This symposium was dedicated to science opportunities with the VLT. All major areas of astronomical research were discussed in the plenary sessions, ranging from where we stand in cosmology to the new frontiers in the solar system. The workshops published in this volume focussed on different ways of finding clusters of galaxies at high redshift, on gravitational lensing by distant compact clusters, on the use of stellar populations as distance, age or abundance indicators, and on the extraordinary progress made in the discovery of extrasolar planets. This book affords a glimpse of what will be at the center of astrophysical research in the forthcoming decade. It is addressed to researchers and graduate students.

An authoritative account of the contributions to science made by the Hipparcos satellite, for astronomers, astrophysicists and cosmologists.

At this conference, both particle physicists and cosmologists presented exciting new results, from experiments that determine with unprecedented accuracy whether the universe is spatially flat, whether it is accelerating and what the nature of the dark matter could be, to more speculative ideas about its origin, based on theories of particle physics which might be confirmed or disproved in the not too distant future. This conference convinced everyone that we are truly living in the Golden Age of Cosmology.

This book is unique in the detailed, self-contained, and comprehensive treatment that it gives to the ideas and formulas that are used and tested in modern cosmological research. It divides into two parts, each of which provides enough material for a one-semester graduate course. The first part deals chiefly with the isotropic and homogeneous average universe; the second part concentrates on the departures from the average universe. Throughout the book the author presents detailed analytic calculations of cosmological phenomena, rather than just report results obtained elsewhere by numerical computation. The book is up to date, and gives detailed accounts of topics such as recombination, microwave background polarization, leptogenesis, gravitational lensing, structure formation, and multifield inflation, that are usually treated superficially if at all in treatises on cosmology. Copious references to current research literature are supplied. Appendices include a brief introduction to general relativity, and a detailed derivation of the Boltzmann equation for photons and neutrinos used in calculations of cosmological evolution. Also provided is an assortment of problems.

This volume reviews the current status with respect to both theory and observation of the extragalactic distance scale. A sufficient accuracy is required both for a precise determination of the cosmological parameters and also in order to achieve a better understanding of physical processes in extragalactic systems. The "standard candles", used to set up the extragalactic distance scale, reviewed in this book include cepheid variables, RR Lyrae variables, novae, Type Ia and Type II supernovae as well as globular clusters and planetary nebulae.

Astrometry from space was performed for the first time and with great success by the ESA Hipparcos satellite (1989-93). This mission was designed as an as trometry mission, but the use of a photon counting detector made it possible to produce very important photometric results: the most accurate astronomical pho tometry ever by the main Hipparcos mission in a very broad band of 120000 stars, and the two-colour Tycho-2 photometry of 2.5 million stars. The cornerstone ESA mission GAIA was approved in October 2000 for launch not later than 2012. This mission will use CCDs in time-delayed integration mode instead of the photo-cathode detectors used in Hipparcos. Due to the higher quantum efficiency of the CCDs, simultaneous integration of many stars, and larger tele scope apertures GAIA will utilize the star light a million times more efficiently than Hipparcos, resulting in astrometry and multi-colour photometry for one billion stars. GAIA photometry is crucial for the scientific utilization of the astrometric results, and the photometric data have a high scientific content in themselves.