Instead of the seven planets in standard geocentric astronomy the Copernican system had only six, the Moon having become a body of kind previously unknown to astronomy, which Kepler was later to call a 'satellite' (a name he coined in 1610 to describe the moons that Galileo had discovered were orbiting Jupiter, literally meaning 'attendant').
Sa halip ng ang pitong planets sa standard geosentriko astronomy, ang Copernican system had lamang ng anim na, ang pagkakaroon ng Moon maging isang katawan ng hindi kilalang uri dati sa astronomy, na Kepler ay mamaya sa tawag ng isang 'satellite' (isang pangalan niya likha sa 1610 upang ilarawan ang Buwan na Galileo ay natuklasan ay orbital Jupiter, literal ibig sabihin 'katulong').