Atacama Large Millimeter/submillimeter Array

The Atacama Large Millimeter/submillimeter Array (ALMA) is a radio observatory in Chile’s Atacama Desert. Its coordinated antennas observe millimeter and submillimeter radiation to study cold gas, dust, and distant galaxies.

Aperture synthesis: An imaging technique that combines measurements from multiple antennas to simulate a much larger telescope aperture. ALMA uses this technique to achieve the resolving power of an array spanning kilometers.
Protoplanetary disk: A rotating disk of gas and dust around a young star from which planets can form. ALMA images disk structures that trace dust growth and possible planet formation.
Millimeter-wave astronomy: Astronomy that observes electromagnetic radiation with wavelengths around one millimeter. ALMA extends this field into the submillimeter range as well.
Nobeyama Radio Observatory: A Japanese radio astronomy observatory in Nagano Prefecture, known for millimeter-wave facilities. Japanese millimeter astronomy experience informed the development of ALMA.
Radio interferometer: A telescope system that combines signals from separated antennas to measure astronomical sources. ALMA is a large, adjustable radio interferometer.
Molecular cloud: A dense, cold interstellar cloud composed mainly of molecular hydrogen and dust. ALMA detects the molecules and cold material within these stellar nurseries.
Submillimeter astronomy: Astronomy using electromagnetic radiation at wavelengths shorter than millimeter waves and longer than far-infrared light. Much of ALMA’s observing range lies in this atmospheric-sensitive part of the spectrum.
European Southern Observatory: An intergovernmental astronomy organization that operates observatories in Chile for its member states. ESO is one of ALMA’s three principal partners and supports its Chilean operations.
Atacama Compact Array: The compact-configuration component of ALMA, comprising twelve 7-meter antennas and four 12-meter antennas. Its closely spaced antennas recover broad structures that ALMA’s main array can miss.
HL Tauri: A young star in Taurus whose protoplanetary disk was imaged by ALMA with prominent concentric gaps. Its detailed 2014 image demonstrated ALMA’s ability to resolve structures in planet-forming disks.

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