Saturday, September 30, 2006

Focusing in on Our Galaxy

Two potential sites have been selected for a highly sensitive radio telescope that could help researchers explore dark energy, gravity waves, and extraterrestrial life.

By David Chandler

This artist's concept shows a section of the five-kilometer-wide central array of the SKA telescope, where half of its collecting dishes will be concentrated. The central area (grey) is made up of flat panels aimed electronically, which can provide a "fish-eye" view of the entire sky. (Courtesy of SKA)

An international plan for the largest-ever radio telescope took a step forward last week with the selection of two possible sites and plans for building prototype systems on each of them.

Slated for completion in 2020, the Square Kilometer Array (SKA) will ultimately be built in either Western Australia (with extensions to New Zealand) or South Africa (with extensions into six neighboring countries). The final site will have an actual collecting area of about one square kilometer, divided up among thousands of dishes, spread out over 3,000 kilometers.

This scale will make it 50 times more sensitive than the Very Large Array (VLA) in New Mexico, even after that telescope's current transformation into the Expanded VLA.

With all that sensitivity, the SKA could bring new power to the search for extraterrestrial intelligence (SETI). The telescope is expected to be so sensitive to the effects of advanced civilizations that it could pick up the equivalent of our airport radar systems coming from anywhere among the nearest million stars in our galaxy.

The SKA will also be able to make a detailed study of the distribution of "dark energy" in the universe, by mapping the distances of a billion galaxies. (One of the most intriguing astronomical findings of recent years, dark energy is found throughout space. It seems to be causing the expansion of the universe to speed up and it accounts for a majority of the universe's "missing" mass.)

The SKA may even be able to indirectly detect gravity waves--which have never been observed but are widely believed to exist--by detecting tiny changes in the precise rate of radio flashes from hundreds of pulsars.

New technology planned for the SKA's central section gives it a sort of radio-frequency "fish-eye lens" that can perform massive, all-sky surveys 10,000 times faster than the Expanded VLA, the largest radio array until the SKA comes online.

The finished SKA telescope will have a central array of approximately 2,000 independently mounted dishes (each 10 to 15 meters across), surrounded by some 200 smaller arrays of about 20 dishes each. (The exact sizes and design of the arrays are still being decided on.)

The concept for the new telescope was based on the Allen Telescope Array (ATA) under construction in California, financed by Microsoft cofounder Paul Allen. That array, which will ultimately include more than 350 individual six-meter dishes, was the first to use standardized, mass-produced hardware instead of the custom-built giant dishes in other radio telescopes. With just 30 of the dishes installed, the ATA is already conducting useful research; one of the major advantages of such modular systems is that even a partial array can be quite powerful.