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ALMA Telescope

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00 Overview

ALMA is a state-of-the-art telescope based on the latest design and manufacturing technologies with the aims of exploring unknown regions of the universe. Here you can understand the entire picture of ALMA from its background to its scientific goals.

Astronomical Observatory Closest to the Universe

ALMA (Atacama Large Millimeter/submillimeter Array) is under construction in the Atacama Desert at an altitude of approximately 5000 meters in northern Chile. The annual rainfall of the area is less than 100 mm, and the sky is always clear almost throughout the year. In the Atacama Desert at high altitudes, incoming radio waves are less susceptible to absorption by terrestrial water vapor and thus we can observe radio waves at relatively shorter wavelengths (at higher frequencies). Combination of these favorable conditions opens the way for the submillimeter observations with ALMA. A flat and wide space of the Chajnantor Plateau is also perfect for the construction of a large-scale array.

It takes one and a half day (including the time for flight connections) to go to the ALMA site from Japan. In spite of such a long distance, this is an ultimate place on earth with ideal conditions for astronomical observations.

ALMA Telescope -Gigantic Eyes Looking Far Out into the Universe-

ALMA is a gigantic radio interferometer array with 66 parabola antennas. ALMA consists of fifty 12-m antennas and "Atacama Compact Array (ACA)" which is composed of four 12-m antennas and twelve 7-m antennas.
By spreading these transportable antennas over the distance of up to 18.5 km, ALMA achieves the resolution equivalent to a telescope of 18.5 km in diameter, as a telescope with the world's highest sensitivities and resolutions at millimeter and submillimeter wavelengths.
ALMA started its construction in 2002, and will start its regular science operation from 2012 JFY.

"ALMA" means "soul" in Spanish (the official language of Chile).

Performance of the ALMA Telescope

Atacama Compact Array, consisting of four 12-m antennas and twelve 7-m antennas, is capable of observing extended celestial objects with high sensitivity. On the other hand, fifty 12-m antennas do not have high sensitivity to extended objects but they can observe compact objects in detail with extremely high resolution. Combining theses data, ALMA can obtain high-fidelity radio-wave images of large to small astronomical objects with high resolution.
The resolution of ALMA is 10 times better than that of Subaru and Hubble Space Telescopes.

Global Collaboration

ALMA is a global collaboration among the National Astronomical Observatory of Japan on behalf of East Asia, National Radio Astronomy Observatory on behalf of North America, and European Southern Observatory on behalf of Europe. The Republic of Chile (host country) also participates in the ALMA project by providing land and cooperation for the construction and operations of ALMA.
The ALMA Project was launched in April 2001 by uniting three different projects of three institutes. Developing three projects into one global partnership led the way to the joint construction and operation of a high-precision gigantic telescope that is difficult to complete for a single institute in terms of resources and costs. Also, cooperation among East Asia, Europe, and North America, sharing tasks in their respective field of expertise, brought about enhanced performance of the telescope.

Japanese ALMA project office is responsible for the developments and manufactures of: the Atacama Compact Array (ACA, high-precision interferometer system) consisting of four 12-m antennas and twelve 7-m antennas; ACA correlator; and three types of receivers focused mainly on submillimeter waves.

Millimeter and Submillimeter Waves

Electromagnetic waves are divided into several classes according to their wavelengths. Light visible to our eyes is a kind of electromagnetic waves called "visible light."
Radio wave closest to infrared rays (at the shortest wavelengths) is called "submillimeter wave" (wavelength: 1 mm to 0.1 mm, frequency: 300 GHz to 3 THz) and the second shortest radio wave after submillimeter is called "millimeter wave" (wavelength: 10 mm to 1mm, frequency: 30 GHz to 300 GHz). Subaru Telescope observes the universe at infrared and optical wavelengths.

We cannot observe dust and gas in the universe with optical telescopes because they are very cold (down to -260C) and do not emit visible or infrared emission. However, with a radio telescope, we can observe such dark regions of the universe through millimeter/submillimeter waves emitted by cold dust and gas.
Until recent years, observation at submillimeter wavelengths was not so common due to technical difficulty and geographical restriction (effected by water vapor absorption); ALMA overcomes these difficulties and opens the way to the submillimeter observations.

What We Can See

When ALMA starts its regular science operation, we can see what has never been observed at optical wavelengths, such as protogalaxies formed in the very early years of the universe, birth of stars and planets like our solar system, and matters related to the origin of life such as organic molecules.

How was our solar system formed? How was the Galaxy holding the Solar System formed? Where did the origin of life come from? By addressing to these questions with ALMA, we will be able to learn the roots of ourselves.

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