Planets

Meaning of Planets

A planet is a celestial body that orbits a star, is massive enough to be rounded by its own gravity, and has cleared its orbital path of other debris. The term “planet” comes from the Greek word planētēs, meaning “wanderer,” as planets appear to move across the night sky relative to the stars.

The International Astronomical Union (IAU) defines a planet based on three criteria:

1. It must orbit the Sun (or a star in the case of exoplanets).
2. It must have sufficient gravity to maintain a nearly spherical shape.
3. It must have cleared its orbit of other debris.

Number of Planets

The Solar System has eight planets classified into two main groups:

1. Inner (Terrestrial) Planets – Mercury, Venus, Earth, and Mars (rocky planets).
2. Outer (Gas and Ice Giants) – Jupiter, Saturn, Uranus, and Neptune (gaseous and icy planets).

Previously, Pluto was considered the ninth planet, but in 2006, the IAU reclassified it as a “dwarf planet” because it does not clear its orbital path.