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[size=117:1zu7wobu]Ghostly ring provides strong evidence for dark matter[/size:1zu7wobu]
16 May 2007
A ring-shaped distribution of mass in a galaxy cluster five billion light-years from Earth is the strongest evidence yet for the existence of dark matter. This is the claim of physicists from the US and Europe, who have used data from NASA's Hubble Space Telescope to see how gravity is bending the light around the cluster. Unlike previous searches in other galaxy clusters, this would be the first time dark matter has been seen isolated in its own separate structure (arXiv.org/abs/astro-ph/0705.2171).
-- a team led by James Jee of John Hopkins University in the US has found a dark matter distribution that they say is completely isolated from the baryonic matter. "In our case, the structure is different not only from the gas, but also from the galaxies," Jee told Physics Web. "In other words, this is the first time that dark matter has been detected in its own structure."
Jee's team made the discovery while analysing Hubble telescope data of how light has travelled through of the galaxy cluster CL0024+17. Over long distances, large masses such as stars inside galaxy clusters can gravitationally bend passing light in a similar way to an optical lens. By using this "gravitational lensing" technique to map the distribution of mass in the cluster, the team were surprised to find that it implied there was a detached ring-shaped structure. "I have looked at a number of clusters, and I haven't seen anything like this," said Jee.
According to physicists studying Hubble Telescope data, the galaxy cluster CL0024+17 could provide the strongest evidence yet for the existence of dark matter. (Image courtesy: NASA, ESA, M J Jee and H Ford)
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