Wednesday, March 31, 2010
Hubble confirms the accelerated expansion of the universe [Hubble]
Astronomers have been studying the results of the biggest survey ever conducted by the Hubble space telescope with an international team of scientists, led by Tim Schrabback of the Leiden Observatory and Ludovic Van Waerbeke of the University of British Columbia. The team has been poring over data covering more than 446,000 galaxies in the hopes to better understand cosmic expansion, using ground-based telescopes to compliment the data. What did they find? Not only is the universe getting larger, but it's getting larger at an accelerated rate.
The technique being used is called weak lensing, whereby astronomers study distortions to find out more about the characteristics of distant galaxies. The heart of the study has been on dark matter: 'Dark energy affects our measurements for two reasons,' the University of Bonn's Benjamin Joachimi said. "First, when it is present, galaxy clusters grow more slowly, and secondly, it changes the way the Universe expands, leading to more distant — and more efficiently lensed — galaxies. Our analysis is sensitive to both effects."
The study also calls back to Einstein, according to Martin Kilbinger from the Institut d'Astrophysique de Paris: 'Our study also provides an additional confirmation for Einstein's theory of general relativity, which predicts how the lensing signal depends on redshift.'
As for the Hubble, its survey saw it circle the Earth 600 times, photograph the same area of the universe with a slight overlap 575 times, requiring 1,000 man hours of observation.
This clearer map, according to Harvard's William High, made all the difference: 'Before, most of the studies were done in 2D, like taking a chest X-ray. Our study is more like a 3D reconstruction of the skeleton from a CT scan. On top of that, we are able to watch the skeleton of dark matter mature from the Universe's youth to the present.'
[DVICE via spacetelescope.org via EurekAlert!]