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Session 50 - Invited Talk.
Invited session, Thursday, June 12
North Main Hall A,

[50.01] ISO's View on the Interstellar Medium and Star Formation

E. F. van Dishoeck (Leiden Obs.)

The Infrared Space Observatory (ISO), launched November 17 1995, provides the first opportunity for spectroscopic observations over the complete 2.4-200 \mum wavelength range above the atmosphere. Its scientific payload consists of 4 instruments: a short wavelength spectrometer (SWS), a long wavelength spectrometer (LWS), a camera (ISOCAM) and an imaging photopolarimeter (ISOPHOT). The two spectrometers provide resolving powers ranging from 200 to 30,000.

The wavelength range covered by ISO is very rich in atomic and molecular lines, so that a wide variety of astrophysical objects (ionized and neutral interstellar clouds, star-forming regions, stars, galaxies, planetary atmospheres, comets) are being observed. In this talk, an overview will be presented of the most exciting new results on the interstellar medium and star formation obtained with the SWS and LWS. These include direct observations of the rotational transitions of the dominant interstellar molecule, H_2, which are readily detected in warm molecular gas found in photon-dominated regions, shocks, and the envelopes and circumstellar disks around young stellar objects. The data provide important constraints on the physical state of these regions, the heating and cooling mechanisms, and the fraction of warm gas at \geq100 K. Other topics include the surprising detection of new solid--state features due to crystalline silicates and PAH's in the mid-infrared spectra of old and young stars and comets, the observation of high ionization lines in planetary nebulae, the identification of new molecules in interstellar ices, and the wealth of data on gas-phase H_2O in a variety of objects. The observations will be discussed in the context of the physical and chemical evolution of low- and high-mass young stellar objects.

Program listing for Thursday