Galaxy Cluster Collision Proves Existence of Dark Matter

Interstellar events may change the face of the universe, but they rarely shake things up on 21st-century Earth. Of course, most interstellar events don’t involve a quadrillion or so stars and create a whole new scientific paradigm. And perhaps even rarer than a popularly-noted astronomical event is a published scientific paper with such a definitive title, but “A Direct Empirical Proof Of The Existence Of Dark Matter” is no ordinary work.

Dark matter has been a puzzle for astronomers since its existence was first postulated by CIT astrophysicist Fritz Zwicky in 1933. While studying the Coma Cluster galaxy cluster, Zwicky calculated the cluster’s mass to be some 400 times greater than previously expected. Until last week, astronomers generally held that there we simply did not understand the composition of 90% of the universe. The problem with dark matter previously had been its very nature, with a pull strong enough that regular matter typically always accompanies dark matter, clustered around the dark matter to hide it from easy observation. Dark matter also cannot be detected with light.

Thanks to one hundred hours studying the galaxy cluster 1E0657-56 on NASA’s Chandra X-ray Observatory, a team led by University of Arizona at Tuscon’s Doug Clowe was able to assemble the new dark matter paper declaring the definitive existence of dark matter. Galaxy cluster 1E0657-56, a.k.a. “The Bullet Cluster” cluster is also known as the bullet cluster, because it contains a spectacular bullet-shaped gas cloud of some 100,000,000 degrees celsius. X-ray images taken at Chandra show the formation is due to interstellar winds produced by the high-speed collision of two galaxy clusters, each formations of tens of millions of galaxies.

Thanks to the collision, called the largest known outpouring of energy since the Big Bang, dark matter and normal matter have been separated, allowing precious X-ray evidence of dark matter. The hot gas in the galaxy cluster 1E0657-56 was slowed by the impact’s drag force, but the dark matter involved was not, because it does not interact directly with itself or the gas except through gravity. If the gas were the most massive component in the clusters, such a separation would not have been seen. Ergo, say the study authors, something with more mass is out there, ergo dark matter.

Upon hearing the news, the grand scope of the results immediately caused waves in the astronomical community. Clowe declared that “These results are direct proof that dark matter exists” and that “We’ve closed this loophole about gravity.” University of Chicago cosmologist Sean Carroll said, “This is the type of result that future theories will have to take into account âÂ?¦ this new result will be impossible to ignore.”

The results will published in an upcoming issue of The Astrophysical Journal Letters. A draft version is available online at http://chandra.harvard.edu/photo/2006/1e0657/media/paper.pdf.

And now that the universe is positively a lot darker, construction of a whole new paradigm in physics has dawned. Who would have thought something so dark would shed so much light on the universe we inhabit? This discovery is truly once in a lifetime.