Giuseppe Piazzi
The astronomer in Palermo who discovered Ceres, the first known asteroid, on the first night of the nineteenth century.
Key facts
- Born
- 1746
- Died
- 1826
- Nationality
- Italian
- Field
- Astronomer and priest
Giuseppe Piazzi was a priest of the Theatine order and a mathematician who founded the observatory at Palermo in Sicily. He spent years making a careful catalogue of the positions of thousands of stars.
On the night of 1 January 1801, while checking star positions, Piazzi noticed a faint object in the constellation of Taurus that was not in any catalogue. Over the following nights it moved slowly against the stars. At first he thought it might be a comet, but it had no fuzzy glow and moved too steadily. He followed it for several weeks until it was lost in the glare of the Sun.
The object was hard to find again. The young German mathematician Carl Friedrich Gauss developed a new method to calculate its orbit from Piazzi's few observations, and at the end of 1801 it was found again almost exactly where Gauss predicted. Piazzi named it Ceres after the Roman goddess of farming and the patron goddess of Sicily.
Ceres orbits the Sun between Mars and Jupiter, in the region now called the asteroid belt. It is about 940 kilometres across, by far the largest body in the belt, and since 2006 it has been classed as a dwarf planet. NASA's Dawn spacecraft orbited it from 2015 to 2018, after visiting Vesta.
On the timeline
- 1 January 1801Piazzi discovers Ceres