2011

ALMA

Radio astronomers are used to working with enormous telescopes that are designed to capture faint signals. Pioneers in the early history of that field were among the first to discover that individual, separate radio telescopes could be linked together in an array—a technique called interferometry—to simulate the resolving power of a single telescope as large as the width of the array. One of the first examples of this technique employed on a large scale is the 27-telescope Very Large Array (VLA) facility outside of Socorro, New Mexico, which came online in 1980, and which was most recently upgraded in 2011.

Another even more sensitive array of radio telescopes also came online in 2011, called the Atacama Large Millimeter Array, or ALMA. Sixty-six radio telescopes were deployed at high altitude (an elevation of 16,600 feet [5,060 meters]) in the super-dry Atacama Desert of northern Chile, positioned above most of the water vapor in the Earth’s atmosphere. Without the blocking effects of water vapor, ALMA can detect long-wave (millimeter-wave) infrared radiation from distant galaxies, stars, and even solar system objects, obtaining compositional information that would otherwise require a space telescope. An international consortium of countries from North America, Europe, and Asia built ALMA at a cost of around $1.4 billion, making it the most expensive ground-based telescope facility ever constructed.

ALMA reconstructed view of a protoplanetary disk of gas and dust around the young star HL Tauri.

Results from ALMA have been stunning, especially because the maximum width of the array (10 miles [16 kilometers) provides the ability to resolve finer details than ever before with radio telescopes. A prime early example comes from ALMA images of a nascent solar system forming around HL Tauri, a star in the Taurus constellation: cleared lanes in the dusty disk reveal the presence of newly forming planets around the hot young star. A steady stream of other discoveries continues to come from ALMA, from the nature of hydrocarbons in nearby comets to the detailed interactions of distant starburst galaxies.

SEE ALSO Solar Nebula (5 Billion BCE), Radio Astronomy (1931), NASA and the Deep Space Network (1958), Circumstellar Disks (1984).

A subset of the sixty-six antennae in the Atacama Large Millimeter Array, or ALMA, in the high and dry Chilean desert.