Magellanic Clouds May Be Just Passing Through

Astronomers have measured the 3-D velocities of the Large Magellanic Cloud (shown here) and the Small Magellanic Cloud. They found surprisingly high speeds, which may indicate that the Milky Way is twice as massive as previously thought, or that the Magellanic Clouds are not gravitationally bound to the Milky Way but instead are "just passing through." (Copyright Robert Gendler and Josch Hambsch 2005)