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PN 07/44: Time to overhaul Newton's Theory of Gravitation?

Last Updated on Wednesday, 07 April 2010 13:54
Published on Friday, 26 October 2007 00:00
pn07_44_galaxies.pngPN 07/44 - Time to overhaul Newton's Theory of Gravitation? Galaxy Cluster Models cast doubt on Dark Matter


For almost 75 years, astronomers have believed that the Universe has a large amount of unseen or ‘dark’ matter, thought to make up about five-sixths of the matter in the cosmos. With the conventional theory of gravitation, based on Newton’s ideas and refined by Einstein 92 years ago, dark matter helps to explain the motion of galaxies, and clusters of galaxies, on the largest scales.


ROYAL ASTRONOMICAL SOCIETY PRESS INFORMATION NOTE
Date: 
26 October 2007

Ref.: PN 07/44

Issued by RAS Press Officer:
Robert Massey
Tel: +44 (0)20 7734 4582
Mobile: +44 (0)794 124 8035
RAS Web site: http://www.ras.org.uk

For almost 75 years, astronomers have believed that the Universe has a large amount of unseen or ‘dark’ matter, thought to make up about five-sixths of the matter in the cosmos. With the conventional theory of gravitation, based on Newton’s ideas and refined by Einstein 92 years ago, dark matter helps to explain the motion of galaxies, and clusters of galaxies, on the largest scales.


Now two Canadian researchers at the Perimeter Institute for Theoretical Physics suggest that the motion of galaxies in a distant cluster is more easily explained by a Modified Gravity (MOG) theory than by the presence of dark matter. Graduate student Joel Brownstein and his supervisor Professor John Moffat of the University of Waterloo present their results in a paper in the 21 November edition of Monthly Notices of the Royal Astronomical Society.


The two scientists analysed images of the ‘Bullet Cluster’ of galaxies made using the Hubble Space Telescope, Chandra X-ray and Spitzer infrared observatories and the Magellan telescope in Chile. The Bullet Cluster consists of two merging clusters of galaxies and lies at a distance of over 3 billion light years in the direction of the southern constellation of Carina.


This arsenal of instrumentation gave them maps of the 150 million degree hot gas between the galaxies and show the effect of gravitational lensing, where the gravity of an intervening object – here the Bullet Cluster - deflects the path of light emitted by a more distant galaxy.


Previous studies suggested that the Bullet Cluster clearly demonstrates the presence of dark matter. But when Brownstein and Moffat compared the observed gravitational lensing and distribution of gas with that predicted using MOG theory, they found no evidence for this. In other words, it is more natural to explain the appearance of this cluster using a revised theory of gravitation than by including dark matter.


MOG theory emerges from a generalization of relativity that eluded even Einstein. The theory has been developed by Moffat for nearly thirty years and is now yielding astronomical and cosmological results. It has been used to successfully explain the movement of stars in over 100 galaxies and the motion of galaxies in more than 100 clusters. MOG theory may also explain the apparent anomalous deceleration of the Pioneer 10 and 11 space probes, launched in the early 1970s and now more than 12000 million km from the Sun.


The two physicists are enthusiastic about their findings. Brownstein comments, ‘Using Modified Gravity (MOG) theory, the ‘normal’ matter in the Bullet Cluster is enough to account for the observed gravitational lensing effect. In time, better observations will lead to higher resolution pictures of the systems we are studying. Continuing the search for and then analysing other merging clusters of galaxies will help us decide whether dark matter or MOG theory offers the best explanation for the large scale structure of the Universe.’


Professor Moffat adds, ‘If the multi-billion dollar laboratory experiments now underway succeed in directly detecting dark matter, then I will be happy to see Einsteinian and Newtonian gravity retained. However, if dark matter is not detected and we have to conclude that it does not exist, then Einstein and Newtonian gravity must be modified to fit the extensive amount of astronomical and cosmological data, such as the bullet cluster, that cannot otherwise be explained.’


CONTACT(s):

Joel Brownstein
Perimeter Institute for Theoretical Physics
31 Caroline Street North
Waterloo
Ontario N2L 2Y5
Canada
Tel: +1 (519) 569-7600 ext. 8084
Fax: +1 (519) 569-7611
E-mail: jbrownstein [at] perimeterinstitute.ca


Professor John Moffat
Department of Physics and Astronomy
University of Waterloo
Waterloo
Ontario N2L 3G1
Canada
Tel: +1 (519) 569-7600 ext. 6611
Fax: +1 (519) 569-7611
E-mail: john.moffat [at] utoronto.ca


NOTES FOR EDITORS

Brownstein and Moffat’s full paper will be ‘online early’ prior to publication in Monthly Notices and can be viewed at http://www.blackwell-synergy.com/loi/MNR from Friday 26 October.


The Royal Astronomical Society (RAS), 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 in Burlington House, its London HQ, and throughout the country, 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 3000 members (Fellows) include scientific researchers in universities, observatories and laboratories as well as historians of astronomy and others.


IMAGES:



IMAGE CAPTIONS:
Figure 1. A contour plot of the purported dark matter in the Bullet Cluster. A significant amount of dark matter lies between the two components of the galaxy cluster. Image: J. R. Brownstein & J. W. Moffat, University of Waterloo, Perimeter Institute for Theoretical Physics.


Figure 2. A contour plot of the Bullet Cluster as predicted by MOG theory. There is a complete separation of the galaxy cluster components and no evidence for dark matter. Image: J. R. Brownstein & J. W. Moffat, University of Waterloo, Perimeter Institute for Theoretical Physics.


Figure 3. A composite image of the Bullet Cluster 1E0657-558, courtesy of the Chandra X-ray Observatory. The hot X-ray gas is in red, and the gravitational lensing reconstruction is in blue, both of which are superimposed on an optical image from the Hubble Space Telescope. Image: X-ray: NASA/CXC/CfA/M.Markevitch et al.; Optical: NASA/STScI; Magellan/U.Arizona/D.Clowe et al.; Lensing Map: NASA/STScI; ESO WFI; Magellan/U.Arizona/D.Clowe et al.