ALMA

In search of our cosmic origins

What is ALMA?

High on the Chajnantor plateau in the Chilean Andes, the European Southern Observatory (ESO), together with its international partners, is operating the Atacama Large Millimeter/submillimeter Array (ALMA) — a state-of-the-art telescope to study light from some of the coldest objects in the Universe. This light has wavelengths of around a millimetre, between infrared light and radio waves, and is therefore known as millimetre and submillimetre radiation. ALMA comprises 66 high-precision antennas, spread over distances of up to 16 kilometres. This global collaboration is the largest ground-based astronomical project in existence.

What is submillimetre astronomy?

Light at these wavelengths comes from vast cold clouds in interstellar space, at temperatures only a few tens of degrees above absolute zero, and from some of the earliest and most distant galaxies in the Universe. Astronomers can use it to study the chemical and physical conditions in molecular clouds — the dense regions of gas and dust where new stars are being born. Often these regions of the Universe are dark and obscured in visible light, but they shine brightly in the millimetre and submillimetre part of the spectrum.

Why build ALMA in the high Andes?

Millimetre and submillimetre radiation opens a window into the enigmatic cold Universe, but the signals from space are heavily absorbed by water vapour in the Earth's atmosphere. Telescopes for this kind of astronomy must be built on high, dry sites, such as the 5000-m high plateau at Chajnantor, one of the highest astronomical observatory sites on Earth.

The ALMA site, some 50 km east of San Pedro de Atacama in northern Chile, is in one of the driest places on Earth. Astronomers find unsurpassed conditions for observing, but they must operate a frontier observatory under very difficult conditions. Chajnantor is more than 750 m higher than the observatories on Mauna Kea, and 2400 m higher than the VLT on Cerro Paranal.

A Tour at the Chajnantor Plateau

Virtual Tour at the Chajnantor Plateau

Click on the image to take a Virtual Tour in and nearby Chajnantor.

To visit the ALMA Site, please see Media Visits

Why is ALMA an interferometer?

ALMA is a single telescope of revolutionary design, composed initially of 66 high-precision antennas, and operating at wavelengths of 0.32 to 3.6 mm. Its main 12-metre array has fifty antennas, 12 metres in diameter, acting together as a single telescope — an interferometer. An additional compact array of four 12-metre and twelve 7-metre antennas complements this. The 66 ALMA antennas can be arranged in different configurations, where the maximum distance between antennas can vary from 150 metres to 16 kilometres, which will give ALMA a powerful variable “zoom”. It will be able to probe the Universe at millimetre and submillimetre wavelengths with unprecedented sensitivity and resolution, with a vision up to ten times sharper than the Hubble Space Telescope, and complementing images made with the VLT Interferometer.

Science with ALMA

ALMA is the most powerful telescope for observing the cool Universe — molecular gas and dust as well as the relic radiation of the Big Bang. ALMA will study the building blocks of stars, planetary systems, galaxies and life itself. By providing scientists with detailed images of stars and planets being born in gas clouds near our Solar System, and detecting distant galaxies forming at the edge of the observable Universe, which we see as they were roughly ten billion years ago, it lets astronomers address some of the deepest questions of our cosmic origins.

ALMA was inaugurated in 2013, but early scientific observations with a partial array began in 2011. See press release eso1137 for more information.

The ALMA project is a partnership of Europe, North America and East Asia in cooperation with the Republic of Chile. ALMA is funded in Europe by ESO, in North America by the U.S. National Science Foundation (NSF) in cooperation with the National Research Council of Canada (NRC) and the National Science Council of Taiwan (NSC) and in East Asia by the National Institutes of Natural Sciences (NINS) of Japan in cooperation with the Academia Sinica (AS) in Taiwan. ALMA construction and operations are led on behalf of Europe by ESO, on behalf of North America by the National Radio Astronomy Observatory (NRAO), which is managed by Associated Universities, Inc. (AUI) and on behalf of East Asia by the National Astronomical Observatory of Japan (NAOJ). The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning and operation of ALMA.

Science goals

Star formation, molecular clouds, early Universe.

More about the ALMA Observatory

The ALMA Planetarium Show

"In search of our Cosmic Origins" is an inspiring show, introducing ALMA, the largest astronomical project in existence. Read more at the Cosmic Origins website.

ALMA Trailer

Download this trailer in other formats from the Video Archive.

 

ALMA

Name: Atacama Large Millimeter/submillimeter Array
Site: Chajnantor
Altitude: 4576 to 5044m (most above 5000 m)
Enclosure: Open air
Type: Sub-millimeter interferometer antenna array
Optical design: Cassegrain
Diameter. Primary M1: 54 x 12.0 m (AEM, Vertex, and MELCO) and 12 x 7.0 m (MELCO)
Material. Primary M1: CFRP and Aluminium (12-metre),
Steel and Aluminium (7-metre)
Diameter. Secondary M2: 0.75 m (for 12-metre antennas);
0.457 m (for 7-metre antennas)
Material. Secondary M2: Aluminium
Mount: Alt-Azimuth mount
First Light date: 30 September 2011
Interferometry: Baselines from 150 m to 16 km
Images taken with ALMA: Link
Images of ALMA: Link
Press Releases with ALMA: Link

 

Did you know?
The two ALMA transporters each weigh 132.5 tonnes and have twin engines each rated at 500 kW each (at sea level). This gives a total of about 1400 horsepower, and is equivalent to about 20 "Smart Fortwo" cars.

 

ALMA on Google Maps

The antenna icons in this image show — in real time — the location of the antennas at the Chajnantor plateau (AOS)

 

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