When Captain Keyes Danny Sapani state they are looking for a Goldilocks. This refers to a scientific phrase where perfect conditions exist on a planet in order to support life. It comes from the story of 'Goldilocks and the Three Bears,' where Goldilocks states, "not to hot, not too cold but just right."
Makee told John-117 that the Covenant took the larger keystone to Aspero. There is no Aspero star or planet or planetary system in real universe, in contrast to Libra and Eridanus which are real. Aspero is a halo-world creative imagination.