Here's why:
* The Sun, Earth, The Moon: This phrasing emphasizes the relationship between these three celestial bodies as a system. Think of it as the "Earth system," with the Sun being the primary source of energy and the Moon being a significant gravitational influence. We use "the" to emphasize their unique and specific role in this system.
* Jupiter, Mars, Mercury, Ganymede: These are simply named objects in space. They are not specifically connected to Earth in a way that requires the definite article "the." We could say, "The planet Jupiter," "The planet Mars," etc., but it's not necessary, as the name itself identifies the specific object.
Think of it this way:
* "The" is used for uniqueness and connection: "The Sun" is our Sun, "The Moon" is our Moon, and "The Earth" is the one we live on.
* No "the" needed for simply identifying: Jupiter, Mars, Mercury, and Ganymede are unique in themselves, but not in a special relationship to Earth like the Sun and Moon.
This is a nuanced distinction, but it helps us communicate the specific relationship we are describing.
