A Super-Telescope Goes to Work

The ALMA array, perched on a 3-mi. high plateau in the Chilean desert, will revolutionize stargazing

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Jorge Saenz / AP

Radio antennas are spread out on the terrain as part of one of the worlds largest astronomy projects in the Atacama desert in northern Chile on Sept. 27, 2012.

It’s not often you get to see a telescope dance, but that’s exactly what happened in the thin, dry air of Chile’s Atacama Desert on March 12. That’s when astronomy’s newest, biggest, most powerful stargazing machine was formally dedicated, after more than a year of preliminary operations. As the speeches from various political and scientific dignitaries came to a close, the Atacama Large Millimeter-submillimeter Array, or ALMA — a set of 57 radio dishes perched on the Chajnantor Plateau, some 16,600 ft. (5,060 m) above sea level — began to swivel and sway, in perfect, choreographed unison, as music filled a tent packed with scientific VIP’s.

OK, maybe it was a little over the top, but ALMA’s creators, including scientists and engineers from Europe, North America, Asia and Chile had the right to make a fuss. The $1.3-billion array is a technological tour-de-force that will produce images ten times sharper than the Hubble; study galaxies from the dawn of time; tease out the secrets of solar systems as they form; and more. “Within a decade,” says Leslie Sage, Senior Editor for Physical Sciences at the journal Nature, “ALMA will have revolutionized astronomy more than the Hubble ever has.”

Actually, that revolution has already begun. Even as ALMA’s dishes were performing their coming-out ballet, astronomers were announcing that during its earlier, shakedown runs, the telescope had discovered surprising numbers of so-called “starburst galaxies,” where new suns are being born at a prodigious rate, just a billion years after the Big Bang — which is a billion years earlier than anyone had expected.

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Last year, a team of observers used the array to detect the presence of unseen planets orbiting the star Fomalhaut, inferring the existence of the worlds by their effects on a ring of dust. “These first results are spectacular,” says Pierre Cox, ALMA’s incoming director, “and they were done with a limited number of antennas”—in the case of the planets, with just 15 of what will ultimately be 66 dishes, working in concert.

That’s one big reason the new telescope is so powerful: by combining the signals from all those dishes, ALMA can simulate a single dish as much as 10 miles (16 km) across. That makes ALMA’s images preternaturally sharp.  The powerful detectors at the heart of each dish, meanwhile, cooled to within a few degrees above absolute zero  (-460º F, or -273º C) can sense the ping of incoming electromagnetic radiation with unprecedented sensitivity.

In this case, the radiation in question isn’t ordinary visible light, but rather a form of light that lies in between the infrared and the microwave parts of the spectrum. Some astronomical phenomena, like the rings of cool dust that eventually turn into planets, naturally glow brightest in the millimeter-submillimeter part of the spectrum. Others, such as distant galaxies, start off with a smaller wavelength but their emissions are then stretched into the millimeter-submillimeter region as they cross a universe that’s constantly expanding.

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Unfortunately, this sort of radiation can’t penetrate Earth’s atmosphere very easily, and launching huge radio dishes into space isn’t very practical. So ALMA’s partner institutions — the U.S. National Radio Astronomy Observatory, the National Astronomical Observatory of Japan and the European Southern Observatory — decided to get as close to space as possible. Chile’s Chajnantor plateau is ideal: about half of Earth’s atmosphere lies below it, and the skies above are extraordinarily dry, with little water vapor to distort ALMA’s view.

The downside is that construction workers, engineers and astronomers have to spend their days in a place where altitude sickness is a real concern. Indeed, visitors who come to the so-called “high site,” where the antennas actually sit, are handed disposable oxygen bottles for a quick puff if things start to go hazy. The operations center, where the antennas are assembled and where the inauguration took place, is at a still-lofty but more manageable 9,000 ft. (2,740 m) or so.

By the end of 2013, all 66 of ALMA’s dishes should be installed and fully operational, and the world’s most powerful astronomical instrument will be firmly on the way to making a series of mind-expanding discoveries, including…well, nobody can really say. “We didn’t know what we were going to find with Hubble,” says Ethan Schreier, President of Associated Universities, Inc., which oversees the National Radio Astronomy Observatory, “and most of what we found, we couldn’t have predicted.”

If the same goes for ALMA — and there’s no reason it shouldn’t — it will prove yet again that the British biologist J.B.S. Haldane was dead on when he said, “The Universe is not only queerer than we suppose, but queerer than we can suppose.”

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