Important support for General Relativity came from studies of the precession of the orbit of....what planet?
It wasn't precession, it was rotation of the major axis direction of the elliptical orbit, also called "perihelion shift". The planet was Mercury.
The important support for General Relativity came from studying the precession (specifically, the perihelion shift) of the orbit of the planet Mercury. This phenomenon refers to the rotation of the major axis direction of an elliptical orbit, where the closest point to the sun (perihelion) gradually shifts around the sun over time. According to classical Newtonian physics, the precession of Mercury's orbit was not fully explainable, suggesting that an additional force or effect was at play.
To understand the significance of this precession, Albert Einstein developed his theory of General Relativity, which proposed that gravity is not solely a force as described by Isaac Newton, but a curvature of spacetime caused by massive objects. Einstein's theory predicted that the bending of spacetime by the sun's mass would account for the observed precession of Mercury's orbit. This prediction was later confirmed by the measurements made during the 20th century, providing strong evidence in support of Einstein's General Relativity.