Every single object in the solar system, from the gargantuan sun to the tiniest speck, exerts a gravitational pull on everything else. The solar system is basically a massive game of tug of war, and all of the yanking balances out at a specific point: the center of mass, or "barycenter ." Everything in the solar system orbits around that point. Sometimes, it's almost smack dab at the Sun's center. Right now, the barycenter is just outside the Sun's surface. But it's constantly changing depending upon where the planets are in their orbital paths.