I photographed these antenna groups with pickup trucks amongst them so that you can see how big the ALMA antennas are. These trucks are North American full-size trucks; they are rather bigger than those commonly seen in Japan. However, they look like miniature cars when placed among the ALMA antenna groups.

Combining Antennas of Different Sizes

The 7 meter diameter antennas are gathered together behind the cars. The antennas in the foreground and to the right in the photograph are 12 meter diameter antennas. These are all Japan-made antennas. The United States and ESO manufactured 25 antennas each with diameters of 12 meters. Those antennas are located across a range of up to 16 kilometers. On the other hand, Japan-made small diameter antennas are installed in small compact arrangements. ALMA uses an observation system called "radio interferometry" that combines multiple antennas into a single big telescope. With this system, we can obtain high resolution by combining data from antennas located across an extended range. And we get a wide field of view with antennas that are placed within a small range. By combining them both, ALMA can obtain the detailed structure of large extended celestial objects.

Text by: Masaaki Hiramatsu (NAOJ Chile Observatory)
Translation by: Hiroko Tsuzuki and Ramsey Lundock (Public Relations Center, NAOJ)

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• ALMA