Submillimeter Array

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The submillimeter array under construction in 2002

The Submillimeter Array (SMA) consists of eight 6 m 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 m James Clerk Maxwell Telescope and 10.4 m California Submillimeter Observatory as an interferometer. All of these telescopes are located at Mauna Kea Observatory on Mauna Kea, Hawaii, and they 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 meters (up to 783 meters 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. Here is a satellite view of the array site, in its compact configuration from Google maps.

The SMA is jointly operated by the Smithsonian Astrophysical Observatory and the Academia Sinica Institute of Astronomy and Astrophysics.

[edit] 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 precisely 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.

The SMA has recently been used to discover that Pluto is 10 kelvin cooler than expected. It was the first radio telescope to resolve Pluto and Charon as separate objects.