Giuseppe Piazzi

Giuseppe Piazzi  (July 16, 1746 to July 22, 1826)  Piazzi was an astronomer and a priest of the Theatine order. He is most famous for discovering the first asteroid, which he named Ceres, on January 1, 1801. Ceres was originally considered a planet, but was reclassified as an asteroid in the 1850’s after other asteroids were discovered.  Ceres is by far the largest object in the asteroid belt, and because it is large enough that its self-gravitation squeezes it into a spherical shape, it was reclassified again in 2006 as a “dwarf planet,” as was Pluto.  Among other contributions Piazzi made to astronomy was supervising the compilation of an extensive and very accurate star catalogue containing 7,646 stars, which was published in 1803.  Piazzi also looked for stars with large so-called “proper motion,” an indication that they are relatively close to the solar system and thus good candidates for measuring stellar parallax. In 1804, he identified 61 Cygni as having especially large proper motion, and in 1838 Friedrich Bessel was able to measure its distance from the earth (which is 11.4 light years) using parallax. This is the first star whose distance to earth was measured (other than the Sun).  

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