The Alcor system was an inhabited star system with at least four planets, including Alcor IV. The system was known to Starfleet at least by the 23rd century, although it wasn't yet colonized until sometime between then and the 33rd century.
The Alcor system was a long distance from the location at which the USS Discovery was abandoned for nearly a millenium. The distance was such that crossing it in a Class C shuttlecraft was theoretically possible but a stretch. (ST: "Calypso")