There were five planets that were visible to ancient Greek and Roman astronomers.
They named these planetsafter their gods: Jupiter – the king of the gods, Venus – the goddess of love and beauty. Mars – the god of war, Mercury – the swift messenger of the gods, and Saturn – the god of harvest.
The planets that have been discovered since Roman times have been named for other Greek and Roman gods.
Uranus was named for the Roman god of the heavens.
Neptune for the Roman god of the sea.
Pluto for the god who ruled the underworld of myth, who was able to render himself invisible.
Pluto is no longer considered the ninth planet in the series of major planetary objects, but instead is now just one of the many so-called “dwarf planets.” The debate started anew after the New Horizons mission passed by Pluto in 2015, revealing a world of surprising geological complexity. As of 2017, delegates from the mission are trying to get Pluto’s planet hood status back.
Content for this question contributed by Greg Jones, resident of Soquel, California, USA