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Cornell-Caltech Atacama telescope promises clues about formation of the universe

The Atacama region of northern Chile is one of the highest and driest places on Earth -- a contradictory landscape of parched ground, cool salt lakes, archaeological treasures and the occasional startling band of hot-pink flamingos.

In the coming years, astronomers say, it also will be the source of some of the most meaningful and advanced research in astrophysics: The site of a 25-meter class telescope sensitive enough to offer new clues about the origin and early evolution of stars, interstellar matter, planetary systems and, ultimately, about the formation of the structure in the universe.

Riccardo Giovanelli, Cornell professor of astronomy, is leading the effort to build the telescope, which will have unparalleled sensitivity for detecting light in the submillimeter, or far infrared, range of the electromagnetic spectrum. Radiation at submillimeter wavelengths (longer than visible light but shorter than radio waves) is normally difficult to detect from the ground because it is easily absorbed by water vapor in the Earth's atmosphere. The Atacama Desert's bone-dry climate and altitude of 5,000 meters (16,500 feet) and higher, therefore, make it a unique and ideal spot for ground-based far-infrared astronomy.

Under Giovanelli's guidance, and with private funding from retired businessman Fred Young, Cornell Class of 1964, Cornell signed an agreement with the California Institute of Technology (Caltech) in 2004 to collaborate on the project. Planners hope to begin construction on the Cornell Caltech Atacama Telescope (CCAT) in 2007 and to see first light in 2012.

CCAT will take advantage of a rapidly advancing technological wave: the development of so-called large format bolometer arrays (a bolometer is an instrument for measuring radiant energy). Until a few years ago, submillimeter telescopes formed images by observing one pixel at a time, and currently operating arrays have a few hundred pixels. CCAT will operate with tens of thousands and eventually millions of pixels: a hugely increased capability that will allow researchers to study in detail the formation of galaxies, stars and planets, which are shrouded in clouds of gas and dust that block radiation at optical wavelengths.

"In the submillimeter, you can actually pierce all the way through; you can see the birth of cosmic structure taking place," said Giovanelli.

The telescope will also be a powerful tool for studying objects in the far regions of the solar system. "We don't know how many large solar system bodies beyond Pluto and Charon are out there," Giovanelli said. "Current submillimeter telescopes can detect things as big as Pluto, but nothing much smaller. This telescope will be able to go to sizes all the way down to 50 to 100 kilometers, instead of 1,000 kilometers."

On a much larger scale, CCAT will be capable of conducting unprecedented surveys of extremely distant galaxies, allowing scientists to witness their distribution at the epoch when galaxies were forming. Scientists estimate that galaxies began to form about 1 billion years after the big bang, or between 12 and 13 billion years ago. At that time the rate of star formation was much higher than it is now, releasing a large amount of electromagnetic energy that was emitted at short wavelengths, then subsequently absorbed by gas and dust and re-emitted at much longer wavelengths. The expansion of the universe then shifted that radiation to even longer wavelengths. As a result, much of the light produced by just-forming galaxies reaches us in the far infrared part of the spectrum.

As a survey tool, the Atacama telescope will be 30 times faster than current facilities and much more sensitive, allowing scientists to probe such fundamental questions as how galaxies form and how their clustering properties evolved.

"The farther back in time you go, the less contrasted the pattern of cosmic structure appears," said Giovanelli. "CCAT will tell us how the large-scale structure tapestry of the cosmos changed its look, from the moment when the first galaxies formed until now."

Another significant new telescope will share the desert with CCAT. A $700 million project by the United States, Europe and other partners to build a large array of millimeter antennae is under way and also expected to be complete in 2012. The Atacama Large Millimeter Array (ALMA), which will be operated as a public facility by the National Radio Astronomy Observatory, will use interferometry to obtain extremely high-resolution images of galactic and extragalactic sources.

CCAT's chosen site will be 2,000 feet higher than ALMA's 16,500 feet; but the two facilities, whose strengths complement each other, will be close enough to allow convenient sharing of resources.

"ALMA will be good at making very detailed maps of very small areas," Giovanelli said. With CCAT, "we will be able to image very quickly and with very high sensitivity very large areas. A CCAT image will cover an area thousands of times bigger than an ALMA image. Objects of special interest discovered by CCAT will be later imaged with ALMA in order to detect finer structures. And access to CCAT will give us a huge leverage arm in facilitating our access to ALMA."

A panel of experts appointed by the Cornell and Caltech administrations and chaired by Nobel laureate Robert Wilson of Harvard University agreed. "CCAT will revolutionize astronomy in the far infrared/submillimeter band and enable significant progress in unraveling the cosmic origin of stars, planets and galaxies," the panel reported in February. "CCAT is very timely and cannot wait."

"CCAT will be a very beautiful tool for the study of galaxies at the epoch of their formation," Giovanelli added. "It is going to be the best instrument of its kind in the world. There is no question about it."

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