Origin and Evolution of Interstellar Silicates

One of the biggest surprises of the ISO mission was the widespread presence of crystalline silicates in the universe. Previous studies – largely limited to the atmospheric windows at 10 and 20 mm – revealed scant evidence for crystalline silicate components in space and then mainly in solar systems objects such as comets and interplanetary dust particles. ISO / SWS has revealed the presence of crystalline silicates in Herbig AeBe stars, Asymptotic Giant Branch stars, planetary nebulae, and Luminous Blue Variables. In contrast there is little evidence for the presence of crystalline silicates in the interstellar medium. The spectrum of crystalline silicates is very characteristic for the detailed properties (cation; temperature; structure;…) of the material present and hence these observations provide a new and exciting tool  for the study of interstellar dust.

            It is clear that we are at an exciting junction where infrared spectroscopy of a variety of objects, in combination with detailed laboratory and theoretical studies,  can be expected to lead to significant advances in our understanding of the origin and evolution of interstellar silicates. It is very timely therefore to organize a small informal workshop in order to bring together scientists working in the area of infrared observations of interstellar and circumstellar silicates, observational studies of solar system objects, laboratory characterization of silicate (and other oxide) materials, laboratory studies of solar system materials (meteorites, IDPs) and theorists involved in modeling interstellar dust in these environments to focus on the composition and evolution of interstellar silicates.

            One major aim of this workshop will be to summarize the current knowledge gained from ISO and to confront this with experimental and theoretical studies of the processes important for the origin and evolution of interstellar silicates. Besides cataloging our current knowledge, our aim is also to chart the future. In particular, new exciting observational opportunities arise on the horizon. SIRTF will be launched mid 2002 and SOFIA  will come on line in 2003, providing us with further spectroscopic views of interstellar silicates. The VLT and Gemini will soon be equipped with state-of-the-art instrumentation in the 10 mm window. On a somewhat longer timescale, by the end of the decade, a mid-infrared spectrometer on NGST may become available.

·                     Observations of interstellar and circumstellar silicates

·                     Laboratory spectroscopy of silicates and other oxide clusters.

·                     The physics of the crystalline-amorphous transition

·                     The origin and evolution of circumstellar and interstellar silicates

·                     The relationship between circumstellar, interstellar and solar system silicates.

The meeting will be held at the Lorentz Center at the Rijksuniversiteit Leiden the week of April 17th, 2001 [ to accommodate European customs, starting the Tuesday after Eastern]. The meeting will be highly informal with ample time for informal discussions. Each of the attendees will be provided with a workspace in the Lorentz Center with a PC or X-terminal. In this way we hope to provide a stimulating working atmosphere which will bevery conductive to start up new collaborative projects among the attendees. In line with the informal character and to keep up the pressure on the attendees to the minimum, no written proceedings will appear.