Astronomers reveal invisible galaxies

An international research team has recently shown the previously unknown 10 million galaxies and the largest map of dark matter to date at the 219th American Astronomical Society in Austin, Texas. For the very first time dark matter has been detected.

Associate Professor Ludovic Van Waerbeke of the University of British Columbia (UBC) in Vancouver is one of the team's astronomers involved in the Canada-France-Hawaii Telescope Lensing Survey (CFHTLenS) that enabled the important discovery.

For the last five years, Van Waerbeke and his group have been analyzing survey images from their "MegaCam" – a 340 megapixel field-imaging camera on the CFHT. The telescope's location is on Hawaii's extinct volcano Mauna Kea, and actually rises above the inner atmosphere. Dark matter is unobservable with conventional telescopes, so the team has been researching dark matter by looking for galaxies using a "weak gravitational lensing" technique. Dark matter is massive, so it interacts gravitationally with the rest of the universe, leading to the gravitational lensing effect. It is like looking outside through glass, Van Waerbeke said.

Most of the Universe or 70 per cent is dark. Van Waerbeke said they do not exactly know what dark matter is but they can "feel" its presence because of its mass. Dark matter takes up a lot of space and mass energy while not emitting or scattering light or radiation. Dark matter forms a "cosmic web" pattern that cocoons galaxies, he said. The galaxies imaged by the team's MegaCam were typically around six billion light years away. A light year is the distance a beam of light travels in one year across the vacuum of space.

Van Waerbeke said, by Einstein's General Theory of Relativity, any mass has space-time around it. There is a curvature of space-time. Gravity and dark matter distorts galaxy light. Their telescope image results assessed the effect of gravitational distortion.

Van Waerbeke also said how it's fascinating to be able to see the dark matter using space-time distortion. It gives us privileged access to this mysterious mass in the universe which cannot be observed otherwise. Knowing how dark matter is distributed is the very first step towards understanding its nature and how it fits within our current knowledge of physics.

He also noted on his UBC Web site that understanding dark matter is crucial for better understanding the universe, its structures, galaxy formation and

particle physics. This discovery may possibly lead to tighter constraints on

theories of gravity.