Ja n 19 99 Interstellar Dust in the WIRE to Planck Era

Interstellar dust appears in a number of roles in the inter-stellar medium. Historically, the most familiar one is as a source of extinction in the optical. Absorbed optical and ultraviolet light heats the dust, whence infrared (including near-infrared to submillimeter) emission, the particular theme of this review. In some distant galaxies, most of the luminosity of the galaxy is thus converted into the infrared, though in the Milky Way the situation is not generally as extreme, except in localized regions of star formation. I briefly review the range of physical conditions in which the dust emits in the interstellar medium and the various sizes of dust probed. Of interest astrophysically are observations of both the spectrum and the spatial distribution of the emission, preferably in combination. In the past fifteen year probes of dust emission have advanced significantly: through IRAS, KAO, COBE experiments, IRTS, ISO, and MSX. Satellite and stratospheric observations of dust emission are complemented by ground-based studies, such as imaging and polarimetry in the submillimeter with the JCMT or imaging of reflected light from dust in the near infrared with 2MASS. Looking ahead, the next decade promises to be equally exciting. I give an overview of some of the distinctive features of facilities anticipated in the near term (WIRE), early in the new millennium (SOFIA, SIRTF), and somewhat further out (IRIS, FIRST, Planck).