There are many ways to determine which astronomical body is the largest. One way would be to measure the diameter of each body. The sun, for example, has a diameter of about 1.4 million kilometers, while Earth has a diameter of only about 12,700 kilometers. This makes the sun more than 100 times larger than Earth. However, another way to measure size is by mass. By this measurement, the largest astronomical body is actually Jupiter. Jupiter has a mass of about 1.8 x 10^27 kilograms, which is almost two and a half times the mass of all the other planets in our solar system combined!