Franz Xaver von Zach

It’s the birthday of Franz Xaver von Zach, who was born in 1754 in Pest, Hungary. As a young man, Zach served in the Austrian military. He then embarked on a career in astronomy. In 1786 he became the director of the Duke of Saxe-Gotha-Altenburg’s new observatory in Gotha, Germany. In that capacity, Zach organized an international group, the Celestial Police, which aimed to find the planet predicted to lie between the orbits of Mars and Jupiter. Zach was among the astronomers who, in late 1801 and early 1802, discovered the dwarf planet Ceres. The successful prediction was made on the basis of the Titius–Bode law, which says that, extending outward, each planet is approximately twice as far from the Sun as the one before. The empirical law correctly predicted the orbit of Uranus, but not those of Neptune or Pluto. The law’s physical basis remains unclear.

Date in History: 4 June 1754