The Submillimeter Array (SMA) explores the universe by detecting light of colors which are
not visible to the human eye. It receives millimeter and submillimeter radiation, so named
because its wavelength ranges from 0.3 to 1.7 millimeter, or 0.01 to 0.07 inches.
The main source of millimeter and submillimeter radiation is cold interstellar material. It
consists of gas, dust and small rock-like bodies. This material is also the substance out of which
stars and planets are formed. Detecting submillimeter emission therefore plays a vital role for studying the
birth and death of stars. When stars are born out of dense interstellar clouds, their
first visible light is trapped within them. The SMA can see into those clouds and acquire detailed images of the
submillimeter light and thereby witness the birth of a star where optical telescopes or human eyes
can just see darkness.
The SMA, commissioned in 2003, is located at 4080 m above sea level (13,386 feet) near the summit of Maunakea.
The submillimeter emission from astronomical objects is partially absorbed by water vapor in the
Earth's atmosphere. At sea level, little submillimeter radiation reaches the Earth's surface, and
submillimeter astronomical observations are impossible. By building the SMA on
a high and dry site, the radiation can be detected and measured through this atmosphere window.
The SMA, the world's first imaging interferometric telescope at the submillimeter wavelengths,
consists of 8 movable antennas that can be positioned along the sides of a Releaux triangle to provide optimal imaging quality.
Each antenna is composed of a smooth parabolic reflector 6 meters (19 and 2/3 feet)
in diameter. The signals from the antennas are amplified and combined electronically to give the
resolution equivalent to an antenna of 0.5 km (0.3 miles) across.
More Information about the SMA:
Submillimeter Array by Ray Blundell, 2007 (pdf)
SMA Brochure (pdf)
Submillimeter Array by Paul Ho, James Moran, and Kwok Yung Lo, 2004 (pdf)
Submillimeter Array: Antennas and Receivers by Raymond Blundell (pdf)
CfA Public Affairs Department