And if Vulcan was a primordial black hole of planetary-mass ?

Abstract: In this work, I re-examine the question of a possible explanation for the anomalous advance of Mercury's perihelion by the existence of a hypothetical planet, Vulcan, which I consider to be a kind of primordial black hole of planetary-mass. The detection of this kind of celestial body has become possible with modern experimental techniques, inter alia, such as the Optical Gravitational Lensing Experiment. Recently, an excess of ultra-short microlensing events with crossing times of 0.1 to 0.3 days has been reported, suggesting the possible existence of sub-Earth-mass primordial black holes in our solar system. The primordial black hole Vulcan planetary mass hypothesis could then explain the anomalous advance of Mercury's perihelion under the influence of its gravitational attraction, still remaining hidden from astronomers' telescopes. But in this case, it will also influence the perihelion advance of the other planets. To this end, I first calculate the mutual partial contributions to the perihelion motion of all the planets by two different methods without Vulcan in a model of simplified solar system consisting of the Sun and eight planets. Next, I include Vulcan in this model within the framework of the Newtonian theory of classical gravitation and analyze Vulcan's influence on the perihelion advance of the inner planets, using Vulcan parameters from my previous work. These results are compared with the perihelion advances of the inner planets predicted by the theory of general relativity, and with the data obtained by modern observations.