Classical planet Classical planet In classical antiquity, the seven classical planets were the seven non-fixed astronomical objects in the sky visible to the naked eye: Mars, Jupiter, Venus, Saturn, Mercury, the Sun, and the Moon. The word "planet" comes from two related Greek words, πλάνης "planēs" (whence πλάνητες ἀστέρες "planētes asteres" "wandering stars, planets") and πλανήτης "planētēs", both with the original meaning of "wanderer", expressing the fact that these objects move across the celestial sphere relative to the fixed stars. The term "planet" in modern terminology is only applied to natural satellites directly orbiting the Sun, so that of the seven classical
Circumbinary planet spacecraft, announced the first partial-eclipse-based discovery of a circumbinary planet. The planet, called Kepler-16b, is about 200 light years from Earth, in the constellation Cygnus, and is believed to be a frozen world of rock and gas, about the mass of Saturn. It orbits two stars that are also circling each other, one about two-thirds the size of our sun, the other about a fifth the size of our sun. Each orbit of the stars by the planet takes 229 days, while the planet orbits the system's center of mass every 225 days; the stars eclipse each other every three