Telescopes unite to sharpen their focus


POSTED: Monday, November 17, 2008

MAUNA KEA » Ten telescope dishes have been combined to form the world's most powerful virtual telescope atop the Big Island's Mauna Kea.

Scientists have connected the signals from the individual telescopes to increase their power and observe submillimeter light, which is invisible to the human eye.

When the signals from the telescopes are electronically brought together in a large computer, they form a virtual telescope with a diameter of 2,541 feet, allowing for an exceptionally sharp view.

The virtual telescope is known as the Extended Submillimeter Array, or eSMA. It can detect radiation from parts of the sky where stars, planets and even entire galaxies are being born.

“;The eSMA will allow us to make measurements which were not previously possible,”; said Gary Davis, director of the James Clerk Maxwell Telescope. “;As a consequence, we expect to enhance our understanding of the origins of planets, stars and galaxies.”;

A telescope's power to see faint objects depends on the size of the surface collecting the light. A larger surface results in a better view.

But the ability to build large collecting surfaces is limited by gravity and cost.

The method of combining signals has been used in radio astronomy for more than 50 years, but it is far more challenging at shorter submillimeter wavelengths.

In addition, the water vapor in Earth's atmosphere blocks submillimeter radiation at all but the driest sites and highest altitudes, making Mauna Kea's observatories at 14,000 feet ideal for this undertaking.

“;The eSMA is an example of an international collaboration in astronomy where the result is more than the sum of its parts,”; said Louis Vertegaal, of the Netherlands Organization for Scientific Research.

One of the first observations of the eSMA targeted a bright radio source in a foreground spiral galaxy. It was able to detect the presence of atomic carbon, which plays a role in the formation of life.

In another survey, the eSMA zoomed in on the envelope of a nearby star close to the end of its life. The star is similar to our sun, which is expected to meet a similar fate in 5 billion years.

The eSMA project combines signals from eight dishes with 6-meter diameters with those from the 15-meter James Clerk Maxwell Telescope and the 10-meter Caltech Submillimeter Observatory.