Abstract

The precession of the equinoxes was discovered in the second century BC by Hipparchus, and it was described as a slow revolution of the whole field of stars about the ecliptic poles. This could be explained if the Sun orbited some unseen object. The modern explanation was given by Newton as being the slow rotation of the Earth?s polar axis about the ecliptic poles caused by gravitational forces from the Sun and Moon on the non-uniform mass distribution in the oblate Earth. In the first model, the Earth?s celestial equator is fixed in space, and the celestial sphere appears to rotate. In the modern model, the celestial sphere is fixed, and the celestial equator rotates. These two models are indistinguishable by astronomical observations. This paper computes a range of possible solar orbits, depending only on the assumed mass of the unseen attractor, that were obtained by minimizing the squared error in the ecliptic longitude of Regulus as measured by Hipparchus circa 128 BC, Ptolemy in 138 AD, 11 observations by Arabic astronomers in the period of A.D. 830-975, the modern longitude of Regulus, and the modern precession rate. An intriguing possibility is that many transneptunian objects and long-period comets may orbit the same attractor that the Sun orbits. Pluto could have been captured by the Sun, if it had been deflected by Neptune. The goal of this line of research is to see if there is a particular attractor mass that will cause Pluto to have been captured by the Sun.