(NASA)
Astronomers from the State University of São Paulo determined that the dwarf planet Ceres was not formed in the main asteroid belt.
The team used computer simulations and found that Ceres comes from beyond the orbit of Saturn, and that the large planetesimal that is similar to some Kuiper Belt objects.
Ceres is the largest object in the main asteroid belt and has interesting properties:
Its mass is about 0.33% of the total mass of the Main Belt
It has a low density and low albedo.
It’s similar to carbonaceous chondrites.
Also, Ceres' position in the Main Belt is close to many C-type asteroids, but the wierdly enough, object is not one of them.
Actually, Ceres is more similar to G-type asteroids. It has a partially differentiated structure, and consists of a water-ice-rich mantle and a rocky core.
Ceres' properties make it similar to the largest Kuiper belt objects like Charon, Eris or even Pluto. This raises questions about the origin of the planetesimal.
In particular, the discovery of ammonia ice on the surface of Ceres is considered strong evidence that it formed in the outer solar system, outside the snow line.
Because of this, the hypothesis arose that Ceres could be a planetesimal captured from the outer part of the protoplanetary disk during its interaction with the giant planets described.
The findings
Now the Brazilian planetary scientists have published simulations of the early dynamic evolution of the outer Solar System.
The intention of the team led by Rafael Ribeiro de Sousa is to determine possible mechanisms for the migration of a Ceres-sized object into the Main Asteroid Belt from beyond the orbit of Saturn.
The researchers have determined that the proportion of the population of Ceres-sized planetesimals that fall into the Main Asteroid Belt ranges from 2.8×10–5 to 1.2×10–3.
This percentage depends on the initial position of the object in the outer part of the circumstellar disk.
The captured bodies had a 70% chance of having an orbital semi-major axis between 2.5 and 3 astronomical units
They also had a 33% chance of an eccentricity of less than 0.2%, and a 45% chance of an orbital inclination of less than 10 degrees.
The earlier estimates predicted the existence of 3,600 Ceres-sized planetesimals in the circumstellar disk beyond Saturn's orbit.
That means that the probabilities of capturing a Ceres-sized body into the Main Belt are 15%, 34%, and 51% for the inner, middle, and outer parts. belts, respectively.
The process itself of migration and capture of Ceres into the Main belt took place in several stages.
First, there was a phase of rapid mixing of planetesimals in the outer protoplanetary disk due to scattering processes.
Then the proto-Ceres would come into mean-motion resonance with the giant planets.
After that, it could collide with other migrating objects that were able to increase or decrease the eccentricity of its orbit and eject it into relatively stable regions of the inner asteroid belt.
The parameters of that proto-Ceres object orbit could also be affected by friction from the gas in the disk.
At the final stage, the gas dissipated from the protoplanetary disk, and other external objects were removed, leaving Ceres in a stable orbit in the Main Belt.
Source:
- Icarus: https://www.sciencedirect.com/science/article/abs/pii/S0019103522000549?via%3Dihub
- Space.com: https://www.space.com/simulation-reveals-birthplace-of-mystery-planet-ceres
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