| Astrophysics (Index) | About |
The term millimeter astronomy (or millimeter wave astronomy) indicates the astronomy of observing EMR wavelengths in the general region of a few millimeters (millimeter waves), perhaps also including substantial fractions of a millimeter. Submillimeter astronomy, by definition, applies to shorter wavelengths, but many telescopes span a range substantially extending both above and below a millimeter, and the choice of term incorporated in the telescope's name seems to be a matter of preference and the unwieldy phrase millimeter/submillimeter astronomy is sometimes used as more accurate. By definition, millimeter astronomy overlaps microwave astronomy. The range is substantially blocked by Earth atmosphere, motivating high-altitude observatories (especially in such locations that have especially dry air), as well as airborne and space telescopes.
The millimeter range has an advantage over longer-wave radio astronomy in that the angular resolution produced by interferometry depends upon the wavelength, shorter providing better resolution, and the frequency is just low enough to allow adaptation of the techniques of radio-frequency correlators. Millimeter/submillimeter interferometry such as that of ALMA are producing images with very fine detail.
Virtually any thermal radiation produces wavelengths in this range, it penetrates dust/particles of some sizes, allowing viewing through clouds that block visible light. But it is scattered by other sizes, making, for example, protoplanetary disks observable. It is also the wavelength-range of cosmic microwave background (CMB) studies.