Gravitational lensing in action - faint hints of an 'Einstein ring' forming about light sources which have been 'lensed' by the warping of space-time. If the galactic cluster causing the warping was orientated in a plane that was face-on directly at Earth - the Einstein ring would be much more apparent. Credit: HST, NASA.
Massive galactic clusters – which are roughly orientated in a plane that is roughly face-on to Earth – can generate strong gravitational lensing. However, several surveys of such clusters have reached the conclusion that these clusters have a tendency towards lensing too much – at least more than is predicted based on their expected mass.
Known (to some researchers working in the area) as the ‘over-concentration problem’, it does seem to be a prima facie case of missing mass. But rather than just playing the dark matter card, researchers are pursuing more detailed observations – if only to eliminate other possible causes. (...)
Read the rest of Astronomy Without A Telescope – Through A Lens Darkly (593 words)
© Steve Nerlich for Universe Today, 2010. | Permalink | No comment | Add to del.icio.us
Post tags: The Sunyaev-Zel'dovich effect
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Full story at http://www.universetoday.com/80339/astronomy-without-a-telescope-through-a-lens-darkly/
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