The Tenth Planet of malevolent cyborgs that became a recurring adversary in later "Doctor Who" stories. The "tenth planet" in the title makes reference to a fictional lost planet in Earth's Solar System; at the time of production, the Solar System was generally held to consist of nine planets, prior to the redesignation of Pluto as a minor planet. "The Tenth Planet" is an incomplete "Doctor Who" serial – one of many serials that were affected by the BBC's policy of wiping archived programmes in the 1960s and 70s. Only three of the four episodes are currently held in the BBC archives; the
Stability of the Solar System it. Though they are not technically part of the solar system for the purposes of studying the system's intrinsic stability, they nevertheless can change the system. Unfortunately predicting the potential influences of these extrasolar objects is even more difficult than predicting the influences of objects within the system simply because of the sheer distances involved. Among the known objects with a potential to significantly impact the solar system is the star Gliese 710, which is expected to pass near the system in approximately 1.35 million years. Though the star is not expected to substantially affect the orbits of the major