In what ways are the orbits of comets and asteroids different from the orbits of the planets?

Quick answer:

The orbits of comets are much more elliptical than planetary orbits, and asteroid orbits are less elliptical.

Expert Answers

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Johannes Kepler published his laws of planetary motion in the early 1600s. His laws were a massive step forward in understanding the motion of objects in space, and his first law was a major departure of the current thinking of the time. Prior to Kepler's laws, it was assumed that orbital shapes were perfect circles. The thinking was heavily influence by faith and religion, but Kepler could show evidence that orbital shapes were not perfect circles. The shape of an orbit is an ellipse. An ellipse is a closed curve where the sum of the distances from the edge of the curve to two points inside the curve is always the same. In layman's terms, it looks like an oval. Planets, moons, comets, and asteroids have elliptical orbits, and they change speeds along those orbits. Not every planet has the exact same elliptically shaped orbit either, but they are similar. Comet orbits are noticeably different from planetary orbits. A comet's orbit is highly elliptical, and that means the ellipse is very narrow and stretched out. Some comet orbits will even cross the orbits of several planets as the comet makes its trip around the sun. Most asteroid orbits are very similar to planetary orbits; however, some asteroid orbits are nearly circular.

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