61 Cygni
The star system 61 Cygni, in the Sirius Sector, is advanced by Lord Dorwin as the potential site for a planet of origin for the human species. Lord Dorwin cites 'Sol' (meaning Earth's Sun) and three other planetary systems in the Sirius Sector, along with Arcturus in the Arcturus Sector, as potential original worlds. (This fact seems to be contradicted by information given in Foundation and Earth). Claims were made as early as 1942 that 61 Cygni had a planetary system, though to date, none has been verified. Asimov may have been aware of these claims, and his friend Hal Clement published two novels featuring alien life originating on such a planet.
Read more about this topic: List Of Foundation Universe Planets