The insanely xenophobic Human Imperium has chosen to take a cautious approach to expanding towards the stars. Emphasizing propulsion, construction, and missile technology, the Imperium intends to glaze the surface of any and all lifebearing planets they encounter as quickly as possible.
Alpha Centauri and Sirrius are quite rich with mineral wealth; Sirrius Corporation claimed a stake on Sirrius-I -- a world with enough corundium and duranium (millions of units at accessibilities of 0.9) to fuel an extensive expansion of mineral production. Tritanium and several other elements may be obtained at several of the Alpha Corporation's Centauri settlements. Alpha centauri itself has been a primary focus for human habitation-- it is now the home to 100 million citizens and two planets have been terraformed, and the empire is only in its 18th year.
Industrial expansion is slowing down, focusing now on research laboratories and shipyard capacity. Before the era's incredible scientists (60% bonus at lvl 10 adminstration) die, the research capacity needs to be upped enough to utilize them!