World’s Newest Radio Telescope Set to Reveal Secrets of the Universe

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Southern star trails over ALMA
Photo: ESO/B. Tafreshi (twanight.org)
Spinning southern star trails seen above ALMA

High up on Chile’s cold, dry Chajnantor Plateau, 66 giants stand under the starry night sky. They gaze upwards, moving with the celestial objects on which they have set their sights. These are the powerful antennas of the Atacama Large Millimeter/submillimeter Array (ALMA). The setup has been operational since March 2013, and together the antennas make up the newest, largest, strongest and most expensive radio telescope currently operating on Earth. The images they produce have 10 times the clarity of those yielded by the Hubble Space Telescope.

ALMA antennas on Chajnantor Plateau
Photo: ESO/B. Tafreshi (twanight.org)
ALMA antennas glowing green in the light of other antennas

The array is the result of a collaborative effort between four nations: it’s jointly owned by the US National Radio Astronomy Observatory, the European Southern Observatory and the National Astronomical Observatory of Japan, and it was built with the cooperation of the Chilean government. The total cost of the project was a staggering $1.4 billion.

ALMA on the Chajnantor Plateau
Photo: ALMA (ESO/NAOJ/NRAO)
Chile’s Chajnantor Plateau: If you look hard enough, you’ll see ALMA

The Chajnantor Plateau in the Atacama Desert was chosen because of its arid environment. The site’s altitude of 16,400 feet (5,000 meters), extremely dry conditions, minimal cloud cover and isolation from sources of radio interference and light pollution make it the perfect location for telescopic stargazing.

ALMA from the air
Photo: Clem & Adri Bacri-Normier (wingsforscience.com)/ESO
ALMA dwarfed by the peaks of the Chajnantor Plateau

Conditions on the Chajnantor Plateau may be ideal for astronomical observation, but the location still presents challenges for the telescopic equipment. Because of this, ALMA was built to withstand strong sunlight, high winds, very occasional snowfall, and fluctuating temperatures – which range from -4 F (-20 C) to 68 F (20 C).

ALMA under the Milky Way
Photo: ESO/B. Tafreshi (twanight.org)
The Milky Way shines above ALMA’s antennas.

ALMA’s 66 antennas look more like giant satellite dishes than the shiny telescopes to which we’re perhaps more accustomed. The antennas come in two sizes: 54 of them measure 39 feet (12 meters) in diameter, while the other 12 measure 23 feet (7 meters) across. The sizes of the antennas allow them to detect different wavelengths of radiation.

Star trails over ALMA telescope
Photo: ESO/B. Tafreshi (twanight.org)
A long exposure creates incredible star trails in the Chilean Andes.

ALMA is an improvement on normal optical telescopes because it has the ability to analyze the universe at longer wavelengths than those of visible light, in both millimeter and submillimeter radiation. These wavelengths include infrared light, which occurs in the dust clouds of the earliest galaxies. By studying them, scientists can work out how these first galaxies formed. Meanwhile, the investigation of the shorter submillimeter wavelengths will increase our understanding of the molecules of interstellar gas clouds and their chemical makeup.

ALMA in red light
Photo: ESO/C. Malin
Red glowing ALMA antennas in front of the Milky Way (left) and the Magellanic Clouds (top)

Still, all this fascinating information can only be gleaned if the antennas are “looking” in the right places. Thus, the antennas have been engineered to swivel with an accuracy of 0.6 arcseconds to point at a particular part of the heavens (an arcsecond being 1/3600 of a degree). This is an incredible degree of accuracy and one that the official ALMA Observatory website says would allow the telescope to “pick out a golf ball at a distance of 15 kilometers (nine miles).”

Snow on the ALMA site
Photo: ALMA (ESO/NAOJ/NRAO)
Snow is very rare in this dry, mountainous location.

Given that they weigh more than 100 tons each, we probably wouldn’t consider the ALMA antennas mobile. Yet mobility is an important aspect of how the array functions. Two specially engineered vehicles were created to transport the antennas to the site and to reposition them when needed. This capacity to change the antennas’ positions gives ALMA increased zooming capabilities.

ALMA at test site
Photo: ALMA (ESO/NAOJ/NRAO)
Two ALMA antennas at the test site in Socorro, New Mexico

The antennas that make up the array work together as one single instrument, and the zoom of the combined dishes is a result of the distance between pairs, known as a “baseline.” As the antennas move apart, their field of view becomes smaller and the resolution gets higher. ALMA operators can choose whether they want to see a wide section of the universe or to concentrate on a smaller part with increased clarity.

The ALMA correlator
Photo: ESO
A look at just one section of the incredible ALMA Correlator

Not surprisingly, processing all the information collected requires one of the world’s most powerful super computers. The ALMA correlator is able to perform 17 quadrillion operations per second. Four equal quadrants and more than 134 million processors make up the computer, which is housed in a remote location high in the Andes of northern Chile.

ALMA antennas in the desert
Photo: ALMA (ESO/NAOJ/NRAO), W. Garnier (ALMA)
This scene of some of the antennas looks like it was taken on another planet.

ALMA promises a glimpse back to when the universe was new and distant galaxies were just forming. Astronomers will be able to determine the distance and age of far-off objects, reducing a process that once took hours to a few minutes. ALMA has already discovered starburst galaxies occurring at an earlier period than was previously believed – and that’s just one small discovery; there are plenty more secrets waiting to be unearthed.

ALMA antenna on the Chajnantor plateau
Photo: ESO/José Francisco Salgado (josefrancisco.org)
Three three antennas facing the same direction are being tested for the Commissioning and Science Verification Process.

ALMA is a powerful example not only of what we can achieve through science and engineering, but also through cooperation between nations. After all, the discoveries that will be made by this incredible telescope will enlighten us all about the mysteries of the universe.

Sources: 1, 2, 3, 4, 5, 6, 7

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