They pinpointed the locations of large, dense regions called mass concentrations, or mascons, which are characterized by strong gravitational pull. (solarsystem.nasa.gov)
You'd find Alpha Centauri, Earth's closest star, would have a significantly stronger gravitational pull. (religion.blogs.cnn.com)
since the Sun is the biggest object in our solar system, it makes sense that it would have the strongest gravitational pull, just as it makes sense that we weigh less / have less gravity on the moon since it is not as large or as dense as the Earth. (religion.blogs.cnn.com)