PIAZZI, Giuseppe (1746-1826). Autograph letter signed ("Piazzi"), to D. Gaetano. Palermo, 22 June 1807. 2 pages, 4to, visible area 235 x 176 mm, matted and framed with a portrait of Piazzi, unexamined out of frame, creasing. I HEAR IT IS RUMORED THAT OLBERS DISCOVERED A NEW PLANET. Italian astronomer and mathematician Giuseppe Piazzi (1746-1826), who founded an observatory at Palermo in 1790, writes about scientific books and equipment. He discusses the developments of the micrometer, created by Jesse Ramsden (1735-1800), which was used in gathering readings from at Palermo. He includes a small diagram and writes, "an ocular astronomical micrometer, called a Dinametra, as imagined by Ramsden." He shares the news of Heinrich Wilhelm Matthais Olbers' discovery of the asteroid Vesta on 29 March 1807: "I hear it is rumored that Olbers discovered a new planet." In 1801, Piazzi discovered dwarf planet Ceres, the largest member of the asteroid belt, which was initially believed to be a planet. With the additional discoveries of Pallas (discovered in 1802 by Olbers), Juno (discovered in 1807 by Karl Ludwig Harding), and Vesta, astronomers began to hypothesize about the nature of these celestial bodies, eventually leading to the discovery and designation of the asteroid belt. Ceres and Vesta are now considered dwarf planets, while Pallas and Juno are designated as asteroids.