Binary planetary system

From Tardis Wiki, the free Doctor Who reference

Twin or Sister planets were planets whose features were more or less identical, or at the very least similar, and were usually found nearby each other. This included the lifeforms which inhabited them.

List of twin planet systems

There were also other planets which were very similar. New Earth was a planet which had the same orbit, size, atmosphere and terrain as Earth. (DW: New Earth)

Binary planetary system