The Enterprise's sensors registered the cube as being entirely solid, massing around 11,000 metric tons, and each edge measuring 107 meters. The device remained at a short distance from the Enterprise but would alter it's course to block the Enterprise when she altered her course.
Lieutenant Commander Spock theorized that the cube was a type of space buoy or "flypaper" which was designed to keep the Enterprise in her place and test her capabilities. When Captain James T. Kirk ordered the Enterprise to pull away, the cube began spinning eratically and emitted lethal radiation. With no other choice, Kirk had the cube destroyed by firing the ship's phasers.