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How many arms does the Milky Way have?

Posted by Marc on January 13th, 2010

Two-armed spiral?Interesting new research from a British and an American scientist suggests that our Milky Way has two spiral arms, challenging the conventional model of a four-armed spiral galaxy. Charles Francis and Erik Anderson worked independently to reach their discovery, analysing data from sky surveys to determine how spiral patterns form.

They liken the gravitational field of a galaxy such as our Milky Way to a “giant funnel with spiral grooves. Stars, like rolling marbles, are channeled down the grooves until they build enough momentum to escape. Escaping stars migrate away from the galactic center, crossing over the next highest groove, and eventually falling back into the same groove they came from.”

Further observations will be needed to confirm their conclusions. We await with interest! In the meantime, physics buffs might like to visit this page where Francis argues that employing epicycles (loops) to explain orbital motions unnecessarily complicates galactic dynamics.

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