Aemonus

P2X-555 was a planet that was going to be visited by SG-1 but a solar flare in Earth's sun caused the team to be sent back to 1969; General Hammond knew this was going to happen before it did, however, and so gave Carter a note to himself, telling her not to open it until she was through the gate. After SG-1 came back to the present time, SG-5 were sent to complete their mission.