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Astronomers reveal a cosmic 'axis of evil'

Last Updated on Thursday, 30 June 2011 10:47
Published on Thursday, 30 June 2011 10:40

Astronomers are puzzled by the announcement that the masses of the largest objects in the Universe appear to depend on which method is used to weigh them. The new work was presented at a specialist discussion meeting on 'Scaling Relations of Galaxy Clusters' organised by the Astrophysics Research Institute (ARI) at Liverpool John Moores University and supported by the Royal Astronomical Society.

hs-2008-24-a-large_web
Caption: The Coma Cluster: A massive cluster of galaxies in the local Universe. Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA). Acknowledgment: D. Carter (Liverpool John Moores University) and the Coma HST ACS Treasury Team
Clusters of galaxies are the largest gravitationally bound objects in the Universe containing thousands of galaxies like the Milky Way and their weight is an important probe of their dark matter content and evolution through cosmic time. Measurements used to weigh these systems carried out in three different regions of the electromagnetic spectrum: X-ray, optical and millimetre wavelengths, give rise to significantly different results.

Eduardo Rozo, from the University of Chicago, explained that any two of the measurements can be made to fit easily enough but that always leaves the estimate using the third technique out of line. Dubbed the 'Axis of Evil', it is as if the Universe is being difficult by keeping back one or two pieces of the jigsaw and so deliberately preventing us from calibrating our weighing scales properly.

More than 40 of the leading cluster astronomers from UK, Europe and the US attended the meeting to discuss the early results from the Planck satellite, currently scanning the heavens at millimetre wavelengths, looking for the smallest signals from clusters of galaxies and the cosmic background radiation in order to understand the birth of the Universe. The Planck measurements were compared with optical images of clusters from the Sloan Digitised Sky Survey and new X-ray observations from the XMM-Newton satellite.

ARI astronomers are taking a leading role in this research through participation in the X-ray cluster work and observations of the constituent galaxies using the largest ground-based optical telescopes.

One possible resolution to the 'Axis of Evil' problem discussed at the meeting is a new population of clusters which is optically bright but also X-ray faint. Dr Jim Bartlett (Univ. Paris), who is one of the astronomers who presented the Planck results, argued that the prospect of a new cluster population which responds differently was a 'frightening prospect' because it overturns age old ideas about the gravitational physics being the same from cluster to cluster.

Chris Collins, LJMU Professor of Cosmology, who organised the meeting said: 'I saw this meeting as an opportunity to bring together experts who study clusters at only one wavelength and don't always talk to their colleagues working at other wavelengths. The results presented are unexpected and all three communities (optical, X-ray and millimetre) will need to work together in the future to figure out what is going on.'

 


CONTACTS

Clare Doran, Press and Publications Officer
Liverpool John Moores University
Tel: +44 (0)151 231 3369
Mob: +44 (0)792 999 9460
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Professor Chris Collins
Astrophysics Research Institute
Liverpool John Moores University
Tel: +44 (0)151 231 2918
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Dr Eduado Rozo
Kavli Institute
University of Chicago
Tel: +1 773 702 7851
Email: This email address is being protected from spambots. You need JavaScript enabled to view it.

Dr Jim Bartlett
AstroParticule et Cosmologie
University of Paris
Diderot
France
Tel: +33 1 57 27 60 95
Email: This email address is being protected from spambots. You need JavaScript enabled to view it.

 


IMAGES AND CAPTION

Images are available from http://hubblesite.org/newscenter/archive/releases/galaxy/cluster/2008/24/image/a/

Caption: The Coma Cluster: A massive cluster of galaxies in the local Universe. Credit:
NASA, ESA, and the Hubble Heritage Team (STScI/AURA). Acknowledgment: D. Carter (Liverpool John Moores University) and the Coma HST ACS Treasury Team

 


NOTES FOR EDITORS

The Royal Astronomical Society

The Royal Astronomical Society (RAS, www.ras.org.uk), founded in 1820, encourages and promotes the study of astronomy, solar-system science, geophysics and closely related branches of science. The RAS organizes scientific meetings, publishes international research and review journals, recognizes outstanding achievements by the award of medals and prizes, maintains an extensive library, supports education through grants and outreach activities and represents UK astronomy nationally and internationally. Its more than 3500 members (Fellows), a third based overseas, include scientific researchers in universities, observatories and laboratories as well as historians of astronomy and others.

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