Cosmology study suggests Einstein didn't err after all

An international study involving several University of Victoria researchers is creating quite a buzz in the world of astrophysics.

The first results from the Supernova Legacy Survey, co-led by UVic astrophysicist Dr. Chris Pritchet, suggest that dark energy—the mysterious force believed to be driving the expansion of the universe—behaves just like famed physicist Albert Einstein said it did more than 80 years ago.

When Einstein was working on his theory of general relativity he added a "cosmological constant" into his equations to explain the presumed static nature of the universe. When the universe was later discovered to be expanding, Einstein retracted the cosmological constant, calling it his "biggest blunder."

Based on its ongoing study of exploding stars, known as supernovae, the survey team has concluded that Einstein wasn't far off the mark. The dark energy that is speeding up expansion of the universe is actually within 10 per cent of Einstein's cosmological constant.

"The existence of dark energy is the single most amazing result from the last 50 years of cosmology," says Pritchet. "We have the best measurements on the nature of this dark energy of any group in the world, and these measurements are going to get better and better as we accumulate more supernova observations over the next few years."

The Supernova Legacy Survey is an international collaboration involving about 40 researchers that seeks to discover far supernovae and measure their spectral light to determine distance. This analysis allows the team to make the first precise measurements of the nature of dark energy.

The five-year survey began in 2003 and is the largest observational project of its kind. So far, the team has measured the distance to 71 supernovae that exploded between two and eight billion years ago.

To search for these distant points of light, the team uses a 340-million pixel digital camera known as MegaCam—the world's largest— attached to the Canada France Hawaii Telescope atop Mauna Kea, Hawaii. To record the spectrum of each faint supernova identified by MegaCam, the team uses some of the largest telescopes on Earth.

Their first results, to be published in the journal Astronomy and Astrophysics, fit the most conservative theory of dark energy—that space has an inherent and constant energy density.

"This survey is the world leader in the quest to understand the nature of dark energy," says Pritchet. He oversees supernova observations for the project, provides software for detection and analysis, and leads some of the science, especially on galaxies that contain supernovae.

Other UVic researchers involved in the survey are research associate David Balam, postdoctoral student Dr. Don Neill, and graduate students Melissa Graham and Eric Hsiao.

The survey is funded in Canada primarily by the Natural Sciences and Engineering Research Council, with additional support from the National Research Council's Herzberg Institute of Astrophysics.