The Submillimeter Array


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SMA



The Submillimeter Array (SMA) explores the universe by observing light invisible to the human eye. Researchers use the SMA to study millimeter and submillimeter radiation with wavelengths between 0.3 and 1.7 millimeter (0.01–0.07 inches), about 1000 times longer than optical wavelengths.

Cold interstellar material is the primary source of submillimeter radiation. Consisting of gas, dust, and small rocky grains, this is the raw material for star and planet formation. When stars form, they are cocooned in dense interstellar clouds. The light they emit is absorbed by the surrounding material, obscuring them at optical wavelengths. Submillimeter radiation, on the other hand, passes through allowing the SMA to make detailed images of star formation that are otherwise impossible. The SMA also studies conditions on other planets and comets in the Solar system; the rich chemistry of interstellar material, especially in around old stars; the distribution and structure of interstellar material in the Milky Way and other galaxies; and the evolution of star formation in distant galaxies throughout the history of the universe.

The SMA is located at 4070 m (13,350 ft) above sea level near the summit of Maunakea. Because water vapor in the Earth’s atmosphere absorbs submillimeter radiation, observations are only possible at exceptionally dry locations. On Maunakea, one of the best observing sites in the world, the SMA is above 90% of the water vapor, permitting observations impossible elsewhere.

The SMA is the world’s first imaging interferometric telescope for submillimeter observations. The array consists of eight antennas, each with a smooth parabolic reflector 6 meters (20 ft) in diameter. These antennas can be positioned among 24 pads in four configurations tailored to the scientific requirements of different observations. Signals received at the antennas are amplified and transmitted to a central building where they are combined electronically for analysis. This technique gives the SMA an angular resolution equivalent to a telescope up to 0.5 km (0.3 miles) across.