Background: |
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Planets, comets, asteroids, and anything else moving through the solar system are held on their orbits by the Sun's gravity. Studying the motions of the planets, Johannes Kepler discovered that the motions of objects orbiting the sun could be described by three laws which we now call "Kepler's Laws":
Note that these laws can be applied (with minor modifications) to planets around other stars, moons around planets, and spacecraft moving through the solar system. In fact, knowing these laws, we can calculate the proper orbit and "launch window" to send a space probe to other planets. First, though, we need to learn about a special type of orbit called a "Hohmann transfer orbit." |