Question

Distinguish between the following:

Inferior planets and superior planets

Answer 1

Inferior and Superior Planets

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The five naked-eye planets can be divided into two groups based on where they can be found in the night sky.

• Inferior Planets -- Mercury and Venus

• The orbits of these planets lie inside the orbit of the Earth

  • The Earth can never pass between an Inferior Planet and the Sun.

  • Inferior Planets show the full range of phases from new to full as they (and the Earth) orbit the Sun.

• Inferior Planets are visible against a dark sky only after dusk or before dawn

• They set shortly after the Sun if they are in the sky
• They rise shortly before the Sun if they are in the morning sky



• Superior planets -- Mars, Jupiter, and Saturn

• The orbits of these planets lie outside the orbit of the Earth.

• They can sometimes lie opposite the Sun from the Earth (that is, the Earth can be between them and the Sun).

  • In this position, called opposition they will rise at sunset, be high in the sky at midnight, and set at dawn.
  • At this position they are at their closest point to the Earth.

• At other times superior planets can also be nearly in line with the Sun (conjunction) and thus just as difficult to view as the Inferior planets.
• Because a superior planet never can pass between the Sun and the Earth, superior planets are always seen at (very nearly) full phase.

  • They will never be seen as a crescent or new.