Semi-major Axis

The semi-major axis is a key measurement in describing an orbit, such as that of a planet around the Sun or a satellite around a planet. It is half of the longest diameter of an elliptical (oval-shaped) orbit, essentially representing the average distance between the orbiting object and the central body over one complete orbit. This measure helps determine the size of the orbit; a larger semi-major axis means the object travels farther from the center, affecting the orbital period and overall dynamics of the system. It's a fundamental parameter used in celestial mechanics to understand orbital characteristics.