The opening of the 60-210 µm window by PACS to sensitive photometry and spectro-scopy at high spatial resolution will address a wide range of key questions of current astrophysics concerning the origins of stars, planetary systems, galaxies, and the evolution of the Universe.
- Most of the energy released e.g. in starbursts or AGNs is absorbed by interstellar dust (which prevents observation at shorter wavelengths) and re-emitted in the far infrared and sub-mm domain
- Besides dusty objects also cool and/or distant objects have their emission peak in the far-IR.
- The far-IR also contains many spectral lines from atoms, ions and molecules. Largely unaffected by extinction they provide detailed information on UV radiation, density, temperature, velocities and abundances of ionised and neutral components of interstellar and circumstellar gas.
PACS is also intended to be an important driver for other projects which will explore adjacent spectral regions, such as JWST in the near/mid IR and ALMA in the mm domain.