To account for inconsistencies between Mercury’s predicted and observed orbital path, French astronomer Urbain Jean Joseph Leverrier postulated that a tiny, hypothetical planet, which he named Vulcan, was present within Mercury’s orbit. Sightings of Vulcan were reported until 1878, and Leverrier died believing he had discovered another planet. Eventually, however, the orbital anomalies were explained by Einstein’s general theory of relativity. After what was the hypothetical planet named? Discuss