National Geographic : 2014 Apr
Cosmic Dawn 85 to arrive. Setting them up to work collectively as a single telescope required astonishing precision. They would need to swiv- el together on command and point at the same target in the sky within a second and a half of one another. To merge their signals coherently, a massive supercomputer had to be installed on- site that was capable of adjusting, to within the width of a human hair, the distance the signals traveled through a cable from the antennas to the processing center—while compensating for the expansion and contraction of the cable due to temperature fluctuations. On a bright April morning a panoramic view of the plateau offers a striking juxtaposi- tion of the ancient and the modern. The brown expanse is studded with white dishes that look tiny against the sky’s limitless azure backdrop. Up close, each of the 12-meter antennas towers above the ground, the dish’s surface glinting in the sun. Operated remotely from a base camp, they swivel gracefully in unison at the click of a button, belying their massive weight. Two custom-made 28-wheel transporters, nicknamed Otto and Lore, stand ready to move them to new locations on the plateau as needed. By the time it was officially inaugurated in March 2013, the Atacama Large Millimeter/ submillimeter Array—ALMA—had already be- gun to deliver on expectations. The year before, with only 16 antennas in operation, research- ers led by Caltech’s Joaquin Vieira had peered through ALMA at 26 distant galaxies showing bursts of star formation. They were surprised to find that the galaxies were on average as far as 11.7 billion light-years away, meaning that their star production had been under way when the universe was barely two billion years old. Such frenetic star birth had previously been thought to have begun at least a billion years later. Since ALMA’s inauguration, there has been a steady stream of other discoveries. In July 2013 astronomers reported that the telescope’s observations had helped solve a long-standing puzzle: why massive galaxies are so rare in the universe. ALMA’s high-resolution images of the nearby Sculptor galaxy showed cold, dense gas billowing out from the center of the galactic disk. Astronomers concluded that the gas was being blasted out by winds from newly formed stars, a huge loss of starmaking material that could stymie the galaxy’s future growth. If confirmed in other galaxies, the phenomenon could solve the mystery. True to its promise, ALMA is also helping researchers understand how planets are born. Last year they reported on ALMA’s images of a disk of dust circling a young star—a nursery of planets. The images revealed what appeared to be a dust trap within the disk: a sheltered region where little grains of dust could stick to one an- other and, grain by grain, grow large enough to seed a planet. This was the first ever glimpse into the start of the planet-forming process. These observations are just the beginning. When all of the antennas come on line later this year, ALMA will conjure even finer details of galaxies and star systems. On an arid plateau a few miles from where shepherds once slept, our eyes will open upon an unseen universe. j alma is designed to penetrate the curtains of dust and gas that shroud galaXies, swirl around stars, and stretch through the eXpanses of interstellar space. tune in to Cosmos: A SpaceTime Odyssey, a new series on the national geographic channel on monday evenings.