LLANO DE CHAJNANTOR, Chile — Earth’s largest radio telescope is growing more powerful by the day on this remote plateau high above Chile’s Atacama desert, where visitors often feel like they’re planting the first human footprints on the red crust of Mars.
The 16,400-foot (5,000-meter) altitude, thin air and mercurial climate here can be unbearable. Visitors must breathe oxygen from a tank just to keep from fainting. Winds reach 62 mph (100 km) and temperatures drop to 10 below zero (minus 25 Celsius).
But for astronomers, it’s paradise.
The lack of humidity, low interference from other radio signals and closeness to the upper atmosphere make this the perfect spot for the Atacama Large Millimeter/submillimeter Array, or ALMA, which is on track to be completed in March.
So far, 43 of the 66 radio antennas have been set up and point skyward like 100-ton white mushrooms. Linked as a single giant telescope, they pick up wavelengths of light longer than anything visible to the human eye, and combine the signals in a process called interferometry, which gives ALMA a diameter of 9.9 miles (16 kilometers). The result is unprecedented resolution and sensitivity — fully assembled, its vision will be up to ten times sharper than NASA’s Hubble Space Telescope.
“What surprises me is what is being observed. Until now, we haven’t had such a capable observatory. We’ve never been able to observe with such resolution, such accuracy,” says David Rabanus, ALMA’s instrument group manager.
More than 900 teams of astronomers competed last year to be among the first to use the array, and scientists from around the world are already taking turns at the joysticks.
They’re looking for clues about the dawn of the cosmos — from the coldest gases and dust where galaxies are formed and stars are born, to the energy produced by the Big Bang. So-called birthing clouds of cold gases and debris can look like ink stains with other telescopes, but ALMA can show their detailed structures.
ALMA also reaches farther beyond Earth’s nitrogen-blue skies than any other radio telescope and has already captured images different from anything seen before by visible-light and infrared telescopes. After a 2003 groundbreaking, scientific operations began last year with a quarter of ALMA’s final capacity.
Seeing in three dimensions made possible the recent discovery of a spiral structure surrounding R Sculptoris, providing new insights about how dying red giant stars implode and send off raw material that will later form into other stars. Those results were published in the scientific journal Nature. ALMA has even been able to detect sugar molecules in the gas surrounding a star about 400 light years away, proving the existence of life’s building blocks there.
Jointly funded and managed by the United States, Canada, the European Union, Japan and Taiwan, the $1.5 billion project is an engineering triumph that launches Chile, already home to some of the world’s largest optical telescopes, to the forefront of ground-based space exploration.