Final answer:
Stellar occultations are used to measure the diameter of a Solar System object accurately. They employ the shadowing of stars by objects like the Moon, planets, or companion stars and utilize the timing of these events to calculate the diameter of these objects.
Step-by-step explanation:
Stellar occultations are the most accurate way to measure the diameter of a Solar System object. This method involves an object, like the Moon or a planet, passing in front of a star and temporarily blocking its light. By measuring the time it takes for the occultation to occur, astronomers can calculate the size of the object causing the occultation.
Occultations are more commonly used with the Moon rather than planets because the moon is closer to the Earth, and its relative motion across the sky is faster, offering more frequent occultation events to observe. Eclipsing binary systems also allow astronomers to measure stellar diameters through analysis of their orbital motions.
Astronomers use various methods to determine stellar characteristics. For instance, while spacecraft flybys can provide accurate measurements of mass and radius, which can then be used to calculate density, spectral analysis informs about a star's radius, composition, and motion by utilizing phenomena like the Doppler effect.