The invention relates to a flywheel for stabilising the position of a spacecraft, comprising a hub means (1) for fastening the flywheel, a flywheel ring (4), which externally surrounds the hub means (1) circumferentially at a distance, a support means (3) for supporting the flywheel ring (4) on the hub means (1), and a vibration damping device (6, 8) having a tuned mass damper means (8) which is axially movable back and forth relative to the flywheel ring with respect to a rotation axis of the flywheel.