... Apollo 15: Driving on the Moon . ... Apollo 15 astronaut James Irwin works on the first Lunar Roving Vehicle, before he and fellow astronaut David Scott take it out for a drive. ... Pictured above is the largest ball of stars in our Galaxy. ... Are these galaxies near the center of the largest gravitationally bound concentration of mass yet known? Previously, the cluster of galaxies known as Abell 3627 was largely unstudied because dust in the disk of our own Galaxy obscured much of its light. ...