The Submillimeter Array (SMA) consists of eight 6-metre (20 ft) diameter radio telescopes arranged as an interferometer for submillimeter wavelength observations. It is the first purpose-built submillimeter interferometer, constructed after successful interferometry experiments using the pre-existing 15-metre (49 ft) James Clerk Maxwell Telescope and 10.4-metre (34.1 ft) Caltech Submillimeter Observatory as an interferometer. All three of these observatories are located at Mauna Kea Observatory on Mauna Kea, Hawaii, and can be operated together as a ten element interferometer in the 230 and 345 GHz bands (eSMA, for extended Submillimeter Array). The baseline lengths presently in use range from 16 to 508 metres (52 to 1,667 ft), and up to 783 metres (2,569 ft) for eSMA operations. The radio frequencies accessible to this telescope range from 180 to 700 GHz which includes rotational transitions of dozens of molecular species as well as continuum emission from interstellar dust grains. Although the array is capable of operating both day and night, most of the observations take place at nighttime when the atmospheric phase stability is best.
Science with the SMA
The SMA is a multi-purpose instrument which can be used to observe diverse celestial phenomena. The SMA excels at observations of dust and gas with temperatures only a few tens of kelvins above absolute zero. Objects with such temperatures typically emit the bulk of their radiation at wavelengths between a few hundred micrometers and a few millimeters, which is the wavelength range in which the SMA can observe. Commonly observed classes of objects include star-forming molecular clouds in our own and other galaxies, highly redshifted galaxies, evolved stars, and the Galactic Center. Occasionally, bodies in our own solar system, such as planets, asteroids, comets, and moons, are observed.
- Atacama Large Millimeter Array, under construction in Chile