Brad Murphy, age 13, of Kansas City, Mo., for his question:

Does our sun revolve around a larger sun?

The moon revolves around the big Earth, and the Earth revo1ves around the monster sun. Everything in the heavens is on the move, and it is natural to suppose that the sun orbits some larger object. The sun certainly is on the move zooming through space at about 170 miles a second, and. We travel with it.

It revo1ves in an immense path around the galaxy. With it whirl billions of stars in a vast pin wheeling system. Some travel in fast lanes, and some in slower lanes, but all of them swing around a central hub of the Milky Way. The sun takes many millions of years to complete its revolution around the big starry wheel, and each trip is called a cosmic year.