Submillimeter Array
Encyclopedia
The Submillimeter Array (SMA) consists of eight 6 metres (19.7 ft) diameter radio telescope
s 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 metres (49 ft) James Clerk Maxwell Telescope
and 10.4 metres (34.1 ft) Caltech Submillimeter Observatory
as an interferometer. All of these telescopes 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 m (52.5 to 1,666.7 ), 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.
The SMA is jointly operated by the Smithsonian Astrophysical Observatory
and the Academia Sinica
Institute of Astronomy and Astrophysics.
s 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 redshift
ed galaxies, evolved stars, and the Galactic Center
. Occasionally, bodies in our own solar system, such as planet
s, asteroid
s, comet
s, and moons
, are observed.
The SMA has been used to discover that Pluto
is 10 K-change cooler than expected. It was the first radio telescope to resolve Pluto and Charon as separate
objects.
Radio telescope
A radio telescope is a form of directional radio antenna used in radio astronomy. The same types of antennas are also used in tracking and collecting data from satellites and space probes...
s arranged as an interferometer for submillimeter
Submillimetre astronomy
Submillimetre astronomy or submillimeter astronomy is the branch of observational astronomy that is conducted at submillimetre wavelengths of the electromagnetic spectrum. Astronomers place the submillimetre waveband between the far-infrared and microwave wavebands, typically taken to be between a...
wavelength observations. It is the first purpose-built submillimeter interferometer, constructed after successful interferometry experiments using the pre-existing 15 metres (49 ft) James Clerk Maxwell Telescope
James Clerk Maxwell Telescope
The James Clerk Maxwell Telescope is a submillimetre-wavelength telescope at Mauna Kea Observatory in Hawaii. Its primary mirror is 15 metres across: it is the largest astronomical telescope that operates in submillimetre wavelengths of the electromagnetic spectrum...
and 10.4 metres (34.1 ft) Caltech Submillimeter Observatory
Caltech Submillimeter Observatory
The Caltech Submillimeter Observatory is a diameter submillimeter wavelength telescope situated alongside the James Clerk Maxwell Telescope at Mauna Kea Observatory. It is engaged in submillimeter astronomy, of the terahertz radiation band.The CSO and JCMT were combined to form the first...
as an interferometer. All of these telescopes are located at Mauna Kea Observatory
Mauna Kea Observatory
The Observatories at Mauna Kea, , are an independent collection of astronomical research facilities located on the summit of Mauna Kea on the Big Island of Hawai'i, USA. The facilities are located in a special land use zone known as the "Astronomy Precinct," which is located in the Mauna Kea...
on Mauna Kea
Mauna Kea
Mauna Kea is a volcano on the island of Hawaii. Standing above sea level, its peak is the highest point in the state of Hawaii. However, much of the mountain is under water; when measured from its oceanic base, Mauna Kea is over tall—significantly taller than Mount Everest...
, Hawaii
Hawaii
Hawaii is the newest of the 50 U.S. states , and is the only U.S. state made up entirely of islands. It is the northernmost island group in Polynesia, occupying most of an archipelago in the central Pacific Ocean, southwest of the continental United States, southeast of Japan, and northeast of...
, and can be operated together as a ten element interferometer in the 230 and 345 GHz
GHZ
GHZ or GHz may refer to:# Gigahertz .# Greenberger-Horne-Zeilinger state — a quantum entanglement of three particles.# Galactic Habitable Zone — the region of a galaxy that is favorable to the formation of life....
bands (eSMA, for extended Submillimeter Array). The baseline lengths presently in use range from 16 to 508 m (52.5 to 1,666.7 ), 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.
The SMA is jointly operated by the Smithsonian Astrophysical Observatory
Smithsonian Astrophysical Observatory
The Smithsonian Astrophysical Observatory is a research institute of the Smithsonian Institution headquartered in Cambridge, Massachusetts, where it is joined with the Harvard College Observatory to form the Harvard-Smithsonian Center for Astrophysics .-History:The SAO was founded in 1890 by...
and the Academia Sinica
Academia Sinica
The Academia Sinica , headquartered in the Nangang District of Taipei, is the national academy of Taiwan. It supports research activities in a wide variety of disciplines, ranging from mathematical and physical sciences, to life sciences, and to humanities and social sciences.Academia Sinica has...
Institute of Astronomy and Astrophysics.
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 kelvinKelvin
The kelvin is a unit of measurement for temperature. It is one of the seven base units in the International System of Units and is assigned the unit symbol K. The Kelvin scale is an absolute, thermodynamic temperature scale using as its null point absolute zero, the temperature at which all...
s above absolute zero
Absolute zero
Absolute zero is the theoretical temperature at which entropy reaches its minimum value. The laws of thermodynamics state that absolute zero cannot be reached using only thermodynamic means....
. 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 redshift
Redshift
In physics , redshift happens when light seen coming from an object is proportionally increased in wavelength, or shifted to the red end of the spectrum...
ed galaxies, evolved stars, and the Galactic Center
Galactic Center
The Galactic Center is the rotational center of the Milky Way galaxy. It is located at a distance of 8.33±0.35 kpc from the Earth in the direction of the constellations Sagittarius, Ophiuchus, and Scorpius where the Milky Way appears brightest...
. Occasionally, bodies in our own solar system, such as planet
Planet
A planet is a celestial body orbiting a star or stellar remnant that is massive enough to be rounded by its own gravity, is not massive enough to cause thermonuclear fusion, and has cleared its neighbouring region of planetesimals.The term planet is ancient, with ties to history, science,...
s, asteroid
Asteroid
Asteroids are a class of small Solar System bodies in orbit around the Sun. They have also been called planetoids, especially the larger ones...
s, comet
Comet
A comet is an icy small Solar System body that, when close enough to the Sun, displays a visible coma and sometimes also a tail. These phenomena are both due to the effects of solar radiation and the solar wind upon the nucleus of the comet...
s, and moons
Natural satellite
A natural satellite or moon is a celestial body that orbits a planet or smaller body, which is called its primary. The two terms are used synonymously for non-artificial satellites of planets, of dwarf planets, and of minor planets....
, are observed.
The SMA has been used to discover that Pluto
Pluto
Pluto, formal designation 134340 Pluto, is the second-most-massive known dwarf planet in the Solar System and the tenth-most-massive body observed directly orbiting the Sun...
is 10 K-change cooler than expected. It was the first radio telescope to resolve Pluto and Charon as separate
objects.