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Extreme Observing

The largest ground-based astronomy project of all time perches more than three miles above sea level in one of the driest deserts on Earth. A particularly parched region of the Atacama Desert in South America is the Antofagasta Region, which is where the Atacama Large Millimeter/sub-millimeter Array calls home.

ALMA is the “hardest place on the planet to work” according to astronomer Joaquin Vieira. Vieira, who is an assistant professor of astronomy at the University of Illinois at Urbana-Champaign, knows what it’s like to work in harsh conditions.

Operational antennas of the Atacama Large Millimeter/sub-millimeter Array. Credit: ESO

About six years ago he spent a month and half in the South Pole helping build the 10-meter South Pole Telescope. With that telescope, Vieira and fellow team members surveyed a part of the sky mapping out locations of distant galaxies. Years later, Vieira directed ALMA to that same spot on the sky and, with a team of more than 60 scientists, published the results that reinterpreted our picture of galaxy evolution.

At a young age, galaxies can get dirty. They house large amounts of dust, which absorbs visible light, making them difficult to observe with telescopes like the Hubble Space Telescope. But if you could see in the infrared, like the monster in the film Predator, these galaxies would shine brightly. Vieira and colleagues found evidence suggesting that these galaxies actually form about a billion years earlier than previous estimates.

Since water vapor in the atmosphere absorbs infrared light, astronomers like Vieira want to observe in the driest regions possible. Space telescopes that look in the infrared, like Spitzer, don’t have this problem. Their size, however, limits how far back in time astronomers can observe.

ALMA, on the other hand, will see farther than any infrared instrument before, space or ground-based. Since the telescope is on Earth, it needs to live in extremely dry conditions, which is why designers turned their sites to the Antofagasta Region.

The region drinks in about half an inch of rain each year. That’s one thousandth of an inch a day – not even enough in which to submerge a flea. According to a study published in Science in 2003, the soil is devoid of life and, not surprisingly, hardly any vegetation grows in the arid environment.

The Atacama Desert. 

At the moment, scientists and engineers are in the process of constructing the 66 antennas that, when finished, will mark the completion of ALMA. According to The Independent, construction teams actually live at a base station closer to sea level because they cannot remain too long at ALMA’s altitude where the air is thinner. They work no longer than eight hours each day and have shifts that are eight weeks on and six weeks off.

“Those guys are doing groundbreaking science while they’re building, commissioning and testing all of the problems you face as an instrument builder,” Vieira said, impressed .

In addition to Vieira’s 2013 study that indicated some galaxies form earlier than expected, other teams of scientists are using the operational portion of ALMA to find regions of planetary formation, galaxy collisions, and hot, molecular clouds.

“Half the universe is dust obscured and ALMA was built to study the dusty universe,” Vieira said. “We’re entering into a golden era of ground-based sub-millimeter astronomy.”

Vieira discussed his methods for studying dusty galaxies at last week’s American Association for the Advancement of Science Annual meeting in Chicago, IL.


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