How do we know the mass of Neptune?
A) The orbital speed of Neptune moving around the Sun
B) The periods and sizes of the orbits of the moons around Neptune
C) The size and density of Neptune
D) The period and size of Neptune's orbit around the Sun
E) The distance of Neptune from the Earth and its rotation period

Question

Quizplus · Accepted Answer

The mass of Neptune can be determined by measuring the orbital speed and distance of its moons. By using Kepler's laws and the measured periods and sizes of the moons, the mass of Neptune can be calculated through the application of Newton's laws of motion. Therefore, option B is the correct choice. The other options, such as option A (orbital speed of Neptune around the Sun) and option D (period and size of Neptune's orbit around the Sun) can also provide information but are not as direct as option B. Option C (size and density of Neptune) is not sufficient on its own to determine the mass of Neptune as there could be objects with similar size and density but different masses. Option E (distance of Neptune from the Earth and its rotation period) is also not sufficient to calculate Neptune's mass.

How Do We Know the Mass of Neptune