Observations of infrared cirrus

The observational database and existing models for the physical characteristics of IR cirrus clouds are reviewed. The phenomena are thin, wispy dust clouds observed at all high galactic latitudes surveyed with the IRAS instruments down to scales of 2-4 arcmin. Variations of the densities and brightness temperatures of the clouds at different IR wavelengths are discussed and illustrated with maps generated with IRAS data, noting correlations of the denser concentrations of cirrus with the distributions of atomic hydrogen and CO in the Galaxy. A possibility that cirrus within 100 pc of the sun are remnants from the formation of the solar system is discussed.