VISIR and the formation of stars and planets

The mid-infrared wavelength range is particularly well suited to study warm circumstellar environments, in relation with star and planet formation theories. VISIR is the VLT instrument dedicated to this wavelength range. It win be installed in 2002 at the Cassegrain focus of Melipal, the VLT telescope unit number 3. This cryogenic instrument, optimized for the two mid-infrared atmospheric windows (N and Q bands), combines imaging capabilities at the diffraction limit of the telescope (0.3 arcsec at 10 mum) over a field up to 51 arcsec, and long-slit (32 arcsec) grating spectroscopy capabilities with various spectral resolutions up to 25000 at 10 mum and 12500 at 20 mum. In this paper, the status of the instrument and some examples of observing programs are discussed, with emphasis on the high spectral resolution observing mode, which will give access, in a unique way, to observations of circumstellar warm molecular hydrogen gas from the South hemisphere.