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A Strong Case for Dark Matter:

Space-based telescopes such as the Chandra X-Ray telescope are proving to be extremely valuable in not only observational astronomy, but also in cosmology - the study of the origins or our Universe.

Galaxy rotation, Universe formation and expansion, galaxy formation and the strength of gravity lenses suggest there is a large amount of "something" that exists in the Universe. This "something" is called Dark Matter. The problem with Dark Matter is that it is not visible, and it is non-baryonic - that is it is not like normal matter. Because of its nature, several opponents to the theory of Dark Matter suggest that modification to the standard laws of gravity (called MOdified Newtonian Dynamics, or MOND) can satisfy some of the curiosities observed, like galaxy rotation.

Chandra Dark Matter Image

A Chandra image of merging galaxy clusters, like the image above, offer a rare view of this mysterious material. The special nature of this merging pair of galaxy clusters called the "bullet cluster" - designated 1E0657-56 - allows the shock of normal, hot matter (shown as pink in the image above) to be visibly separate from gravitational effects (shown as blue in the above image).

What makes this cluster so special is the amount of gravity that is present within the proximity of these two merging clusters of galaxies. Normal galaxy clusters - if an image like the one above were taken - would also contain the blue, but would be hidden by the pink. The collision of 1E0657-56 allows for this visible separation of gravity and matter.

While this evidence only supports intergalactic Dark Matter, the presence of this will not require any modifications to Newtonian Dynamics.

For more background information, see Dark Matter, Galaxy Clusters and Galaxy Mergers.


Original Story: Science 25 August 2006: Vol. 313. no. 5790, p. 1033 DOI: 10.1126/science.313.5790.1033


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