Answer: The part of the X-ray machine that aims at the central ray is the collimator.
The collimator is a device attached to the X-ray machine that shapes and directs the X-ray beam by limiting its size and shape. It helps to minimize patient exposure to radiation by only allowing the specific area of the patient's body to be imaged to be exposed to radiation, thus reducing unnecessary radiation exposure to other parts of the body. The central ray is the center of the X-ray beam, which is directed by the collimator to the specific area of the patient's body being imaged.