News Release

New study questions dark matter in galaxies and clusters of galaxies

Novel approach may help lead to an explanation of the Pioneer 10 - 11 spacecraft anomaly

Peer-Reviewed Publication

Perimeter Institute for Theoretical Physics

A new paper examines galaxy rotation curves without exotic dark matter and seeks to describe a modified Newtonian acceleration law derived from a relativistic modification of Einstein's gravitational theory. Details are available in the January 10th, 2006, edition of The Astrophysical Journal 636, pp. 721-741. The study is entitled "Galaxy Rotation Curves Without Non-Baryonic Dark Matter" and is co-authored by John Moffat, Perimeter Institute for Theoretical Physics, and Joel Brownstein, Perimeter Institute for Theoretical Physics.

This work, in conjunction with other research, may one day help to explain the Pioneer 10 - 11 spacecraft anomaly. The two space probes, launched in 1972 and 1973 respectively, are now at the edge of the solar system on trajectories that cannot yet be fully explained based on what is known about Newtonian and Einstein gravity.


Joel Brownstein is available at or 519-569-7600 ext. 8061.

About Moffat and Brownstein:
John Moffat is a theoretical physicist who was born in Denmark, earned his PhD at Trinity College, Cambridge University, U.K., and now resides in Waterloo, Ontario, Canada. He recently spoke at the International Space Science Institute in Bern, Switzerland on the subject of the Pioneer anomaly. He is also noted for his personal correspondence, in earlier years, with Albert Einstein. Joel Brownstein is Canadian and holds a Natural Sciences and Engineering Research Council of Canada (NSERC) graduate student scholarship. He conducts research operations at Perimeter Institute concurrent with studies in the Physics Department at the University of Waterloo.

About Perimeter Institute:
Canada's Perimeter Institute for Theoretical Physics is a non-profit scientific research and educational outreach organization located in Waterloo, Ontario, Canada – just outside Toronto. The award-winning centre is home to a diverse group of international scientists who contemplate new ideas about the ultimate nature of space, time and matter. For more information please visit

For media inquires please contact John Matlock at or call 519-569-7600 ext. 6081.

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