Ceres’ Occator Crater in false colour showing surface composition via NASA’s Dawn spacecraft/ JPL/ Caltech/ UCLA/ MPS/ DLR/ IDA.
On January 1, 1801, an Italian priest, mathematician and astronomer Giuseppe Piazzi discovered the first asteroid, now called Ceres. It orbits in the asteroid belt, between the orbits of Mars and Jupiter. These days, Ceres is no longer classified as an asteroid, however. In 2006, the International Astronomical Union decided Ceres was big enough to be designated a dwarf planet. Ceres became the first-ever dwarf planet to be orbited by a spacecraft, from 2015 to 2018, when NASA’s Dawn mission peered down at Ceres and unlocked some of its mysteries.
The story of the discovery of Ceres goes back to German astronomer Johannes Kepler and to Tycho Brahe, a Danish nobleman and inveterate night sky observer, in the 1500s. When Kepler obtained Tycho’s astronomical data, he searched it for the explanation behind the motion of the planets, in particular Mars’ retrograde motion. This work led Kepler to what is one of his most praised discoveries, what we today know as Kepler’s three laws of planetary motion.
However, Kepler’s analysis also led him to discover something else. He noticed an unusually ...