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Discoveries > Asteroids II


Asteroids have a stellar aspect and they are identified only through their fast motion on the sky. Several pictures taken time to time or visual observations of well-known fields of stars could put into evidence these moving stars.

Ceres was discovered on January 1, 1801, by Giuseppe Piazzi, director of the Palermo Observatory in Sicily. Piazzi sought to observe a star called Mayer 87 and instead he observed an object moving over the celestial sphere, which he first took for a comet. 24 successive observations from January 1 to February 11 convinced Piazzi that it was not a comet but a planet. His discovery was followed by many others during the nineteenth century showing a new category of objects, the asteroids.

Previously, astronomers had noticed the lack of a planet between Mars and Jupiter as predicted by Bode's law, totally empirical and not based on scientific bases but instituting a logical sequence of distances of the planets to the Sun. The discovery of Ceres answered this question: the missing planet was found! Unfortunately, it was not so: Ceres was too small for a planet, its orbit was not circular and Ceres was not alone but other similar and numerous bodies were found soon after.

Left, Giuseppe Piazzi who discovers Ceres. At right, le list of planets as published in the Connaissance des temps for 1808.
Credit :  DR