PHYS 284 Lecture Notes - Lecture 7: Planetary Science, Earth Mass, Galilean Moons
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Other times we compare the worlds to one another, seeking to understand their similarities and differences. Note that astronomers use the term planetology broadly to include moons, asteroids, and comets as well as planets. These lessons help us understand both the general principles that govern planetary systems and the specific circumstances under which earth-like planets and possibly life might exist elsewhere. The comparative planetology approach should also benefit you as a student by helping you stay focused on processes rather than on a collection of facts. The sun: radius: 696,000 km = 108rearth, mass: 333,000mearth, composition (by mass): 98% hydrogen and helium, 2% other elements. The sun is by far the largest and brightest object in our solar system. It contains more than 99. 8% of the solar system"s total mass, making it nearly a thousand times as massive as everything else in the solar system combined.