"Infrared Cirrus": New Light on the Interstellar Medium

The terminology "infrared cirrus" was introduced to describe complex extended sources of infrared emission apparent in the data from IRAS. It shows in detail the global distribution of the material long known to obscure shorter wavelength observations of our Galaxy and beyond. It also provides new insights on topics ranging from the nature of interstellar grains to the interpretation of the infrared energy distributions of galaxies. The high galactic latitude cirrus is correlated both with atomic gas and with diffuse molecular clouds in the solar vicinity. The status of both global and specific cirrus cloud studies is reviewed, and implications for dust and cloud properties are discussed.