Note 3 — FIRST PART. The Story of Astronomy from Primitive Times until the Age of Dante.

Greek planetes, a wanderer. This name was originally given to Mercury, Venus, Mars, Jupiter, Saturn, and also to sun and moon, for it indicated all the known heavenly bodies which changed their places among the stars. In modern usage it is not applied to the sun, but only to his satellites, of which many more are now known.