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The Difference Between Inferior Planets and Superior Planets

Astronomers classify planets as "superior" or "inferior" depending on their distance from the sun in relation to Earth. Earth and other planets move around the sun in the same direction, in a circular motion. The famous astronomer Copernicus discovered the order in which the planets rotate around the sun and also the size of their orbits, using the concept of elongation. Copernicus̵7;s findings led to the classification of planets as inferior or superior.

Superior and Inferior Planets
- The distance between the sun and a planet determines the planet̵7;s path across the sky. Planets closer to the sun than to Earth are inferior planets. This includes Mercury and Venus. Planets that are farther away from the sun than Earth is are the superior planets. This group includes Mars, Jupiter, Saturn, Uranus and Neptune. (Formerly, Pluto would have been included in this group, but its status has been downgraded to a "dwarf planet.")
Conjunction
- When a planet is in line with Earth and the sun, there is said to be a conjunction. When this occurs, the planet and the sun appear at almost the same position in the sky to people on Earth. An inferior conjunction occurs when a planet comes between Earth and the sun. A superior conjunction occurs when the planet gets beyond the sun and Earth. When a planet is not in conjunction, there is an angle between the planet and the sun. Astronomers call this a planet̵7;s elongation.
Inferior Planet Elongation
- For Mercury, elongation can range from 0 to 28 degrees. In the case of the other inferior planet, Venus, elongation ranges from 0 to 47 degrees. These planets are farthest west from the sun when it is sunrise for us, and they are farthest east from the sun when it is our sunset.
Superior Planet Elongation
- The elongation of superior planets can range from 0 to 180 degrees. When a planet̵7;s elongation is 180 degrees, it is on the other side of Earth and away from the sun. Astronomers also refer to a 180-degree elongation as an opposition. Inferior planets don̵7;t have the capability to assume an elongation of 180 degrees.

Astronomy