Dark Flow Discovered Outside Observable Universe

Thursday, September 25 2008 @ 03:32 am EDT

Contributed by: dgrosvold

Hot gas in moving galaxy clusters (white spots) shifts the temperature of cosmic microwaves. Hundreds of distant clusters seem to be moving toward one patch of sky (purple ellipse). Credit: NASA/WMAP/A. Kashlinsky et al.

Scientists have discovered that giant clusters of galaxies are being pulled in a uniform direction apparently by gravitational forces that can't be explained by known phenomena in the observable universe.

Researchers have concluded that based on recent studies, these forces are ostensibly from outside the observable universe, not within it. Remember, the observable universe is only that part we can see. We see out to only the part within a sphere that extends to the distance coinciding with the estimated age of the universe — or approximately 13.7 billion light years. Based on the fact that the universe is expanding at an ever-faster rate, it's highly probable that there are regions beyond our ability to see. In other words, regions of space more than 13.7 billion light years distant. So distant that the earliest light that left these regions has not yet reached our corner of the universe.

Cosmologists are calling the phenomena Dark Flow. This is separate and distinct from the forces causing the acceleration of expansion in the universe, which is known as dark energy. This dark flow is causing large-scale galaxy clusters to move rapidly toward a reqion of space in between Centaurus and Vela. The speed is estimated to be on the order of 2 million mph (3.2 million kph,) and doesn't decrease with distance as far as researchers can measure.

See the original article on space.com for more information.

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