At the dawn of the 19th century, the celestial police were on patrol. They were looking for a planet between the orbits of Mars and Jupiter. And on the century’s first day, a future squad member found one – sort of. Later discoveries showed that it wasn’t a planet at all, but the first and largest member of the asteroid belt – a wide band of millions of rocky bodies.

Astronomers were looking for a planet because of the numbers. There seemed to be a mathematical relationship between the distances from the Sun to the known planets. But there was a gap between Mars and Jupiter. So one astronomer began organizing a search party: the celestial police.

Giuseppe Piazzi, at the Palermo Observatory in Sicily, was on the list of people to invite. But he was already searching on his own. And before he got his invitation, he found something – 225 years ago today. Piazzi originally thought it was a comet – but hoped for something bigger.

As other astronomers began studying it, they decided it was the sought-after planet. They named it Ceres, for the Roman goddess of agriculture.

Within a few years, though, they’d found several other bodies in similar orbits. So they realized that Ceres wasn’t a planet at all, but just one member of a band of debris – the asteroid belt.

Today, Ceres has regained its planetary status – sort of. It’s a dwarf planet – the only one in the inner solar system.

Script by Damond Benningfield