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PLANETS AND THEIR SATELLITES

orbit of the earth. This class comprises only Mercury and Venus.

Superior planets are those whose orbits lie without that of the earth. These comprise Mars, the minor planets or asteroids, and all four of the outer group of major planets.

Fig. 27.—Orbits of the Four Inner Planets.

When a planet seems to us to pass by the sun, and so is seen as if alongside of it, it is said to be in conjunction with the sun.

An inferior conjunction is one in which the planet is between us and the sun.

A superior conjunction is one in which the planet is beyond the sun.

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