Light shines on 'dark energy'

From the Hubble telescope in space and mountaintop observatories around the world, astronomers are finding dramatic new evidence of how galaxies evolved over billions of years, with mysterious "dark energy" distorting their shapes and massive black holes gobbling up stars within them.

That picture emerged last week at a meeting of the International Astronomical Union in Sydney, Australia, where international astronomers are reporting on their latest discoveries. The findings are made possible by technologies that researchers say are transforming the science of astronomy.

A team led by University of California astronomers, for example, is using the giant telescope and a new detector at the Keck Observatory atop Mauna Kea, Hawaii, to collect the light from galaxies as they existed more than 7 billion years ago — half as old as the universe itself.

In their first report on a project called DEEP2, the California scientists have found that even then the new galaxies were gathering into clusters interspersed with long filaments of gas and apparently empty voids that may hold invisible "dark matter," said Santa Cruz astrophysicist David Koo in a phone interview from Sydney.

"Looking back that far is like looking at a section of the universe as it existed long before our Earth was formed — perhaps even before our own Milky Way was formed," Koo said. "We are seeing regions where starry masses are sponge-like or foamy, and we can watch how the galaxies were evolving."

Their findings were made using a 10-ton instrument called a spectrograph that analyzes the wavelengths of light from 130 galaxies at a time. It is the most powerful and precise of its kind ever built for observing the most distant objects in the universe.

The ambitious galaxy survey project will observe and map at least 50,000 galaxies over the next three years, extending back in age as far as 9 billion years.

In recent years, physicists and astronomers have puzzled over the fact that all the visible matter in the universe — the planets, stars, galaxies and superclusters of galaxies — account for only about 5 percent of the matter the universe must hold if cosmological theories are correct.

Another 30 percent, the scientists hold, is invisible dark matter. And the rest isn't even matter at all but dark energy — a kind of repulsive force that astronomers believe keeps the universe expanding faster and faster forever instead of collapsing by gravity into some kind of cosmic Big Crunch.