Hawaii-based telescope to search dark side of universe

BY STEPHEN STRAUSS

A group of Canadian astronomers has announced that for the next five years, they and the clear-eyed Hawaii-based telescope they dote on are literally going over to the dark side.

Specifically, most of the 3.6-metre Canada-France-Hawaii telescope's exploration time will be used in an attempt to uncover the nature of the mysterious dark matter and dark energy that give shape and form to the universe.

While the search for the meaning of darkness will be made in conjunction with French astronomers, its one essential partner will be Megacam.

The world's largest astronomical camera, the $5-million (U.S.) Megacam is capable of taking a picture across a distance four times the size of the moon as it appears in the night sky.

And because it uses the charge-coupled devices now common in digital cameras, Megacam can capture 80 to 90 per cent of the light that falls on its nearly 73-square-metre viewing area. That compares with the 1 per cent of the sky's light that can be recorded on a classic photographic plate.

Image size and quality is important because at the end of five years, upwards of two million galaxies will have been captured by Megacam in what National Research Council astronomer David Schade describes as "the biggest sure thing in the project."

That is a measure of the amount of dark matter in the universe. Astronomers have long argues that the shape and physical characteristics of the universe imply that more than 90 per cent of the material in it is invisible.

The only way to see the invisible, in large part probably unlit stars and dust, is to record the way in which light from distant galaxies is bent by the gravitational fields of the dark matter.

When all the Legacy Survey gravitational bending is analyzed, not an easy job given that the telescope will generate 20 to 30 trillion bits of information a year, it should provide astronomers the largest dark matter map ever made.

The second dark thing the Legacy Survey will seek to understand is what is known as dark energy, a repulsive force recently proposed as an explanation of why the universe is apparently picking up speed as it ages.

"The force is there, but we don't know what it is," Mr. Schade said.