The Sigma Erandi system is a star system.

When the USS Enterprise-D purchased hytritium needed on Beta Agni II from Kivas Fajo in 2366, Fajo told the crew that the next closest source of hytritium was Sigma Erandi, but he could not guarantee they had any on hand. The system was also three weeks away from the Enterprise's current position, so the USS Grissom, the Starfleet vessel closest to Sigma Erandi, was informed to stand by in case more hytritium was needed. (TNG: "The Most Toys")