Alpha orbits the star Alpha Centauri A (only 4.2 ly from Sol). The Empire terraformed this planet to hold Earth's inhabitants after it was devastated by radiation, but the project was never completed. Covered almost entirely with water, this planet was considered by Lord Dorwin to be the origin system of humanity. About halfway into the 1000-year darkness after the fall of the Empire, Golan Trevize ventured to this planet in his search for Earth. The inhabitants seemed nice enough, but tried to infect him and his crew with a disease. After leaving, Trevize headed to the Solar System.