Question

california standards check 8.4.e know the appearance, general composition, relative position and size, and motion of objects in the solar system, including planets, planetary satellites, comets, and asteroids. 17. identify relationships some of the moons of the gas giants are larger than mercury. why are they not considered to be planets? __________________ ________________ __________________

Explanation:

According to the International Astronomical Union (IAU) definition of a planet, an object must orbit the Sun (or a star in general for exoplanets), be spherical (hydrostatic equilibrium), and have cleared its orbit of other debris. Moons of gas giants orbit a planet (not the Sun directly) and thus do not meet the first criterion of the IAU planet definition.

Answer:

They are not considered planets because they do not orbit the Sun directly. Planets must orbit a star (in our solar system, the Sun), while these moons orbit a gas - giant planet.