Ceres probably formed farther out in the solar system and migrated inward
When Sicilian astronomer Giuseppe Piazzi spotted Ceres in 1801, he thought it was a planet. Astronomers didn't know about asteroids at that time. Now we know there's an enormous quantity of them, primarily residing in the ...
Ceres is about 1,000 km in diameter and accounts for a third of the mass in the main asteroid belt. It dwarfs most of the other bodies in the belt. Now we know that it's a planet—albeit a dwarf one—even though its neighbors are mostly asteroids.
But what's a dwarf planet doing in the asteroid belt?
A new research article provides the answer: Ceres didn't form in the asteroid belt. It formed further out in the solar system and then migrated to its current position. This isn't the first study to reach that conclusion, but it adds weight to the idea.
The article is "Dynamical Origin of the Dwarf Planet Ceres," and it's published in the journal Icarus. The lead author is Rafael Ribeiro de Sousa, a physics professor at Sao Paulo State University in Brazil. Other co-authors come from the same university and France and the U.S.
(Note: Ceres is called a dwarf planet, a protoplanet, and sometimes an asteroid. No point getting hung up on it. It was officially classified as a dwarf planet in 2006.)
Ceres is one of three dwarf planets or protoplanets in the asteroid belt. The other two are Vesta and Pallas. A fourth large body, Hygiea, is 434 km in diameter and may also be a dwarf planet. These four largest bodies make up half the mass of the asteroid belt.
This image of Ceres approximates how the dwarf planet’s colours would appear to the eye. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
These are the four largest objects in the asteroid belt. Ceres is the only one massive enough for self-gravity to collapse it into a spheroid shape. Credit: ESO/M. Kornmesser/Vernazza et al./MISTRAL algorithm (ONERA/CNRS)
Compounds like ammonia condense beyond the Solar System’s frost line. Since Ceres contains ammonia, it likely formed beyond the frost line. Credit: NASA / JPL-Caltech, InvaderXan of http://supernovacondensate.net/.