For the past many years, I’ve found myself repeating over and over, “If anyone tells you they know how the solar system formed, they are lying.” As of the time of this recording, January 6, 2022, I’m willing to say that at least one team may actually have started to unlock this issue. 

In new models published in Nature, a team led by Andre Izidoro was able to evolve a disk of material around a young star into the solar system we see today, complete with, and here I quote from the press release:

• “An asteroid belt between Mars and Jupiter containing objects from both the inner and outer solar system.
• The locations and stable, almost circular orbits of Earth, Mars, Venus, and Mercury.
• The masses of the inner planets, including Mars, which many solar system models overestimate.
• The dichotomy between the chemical makeup of objects in the inner and outer solar system.
• A Kuiper belt region of comets, asteroids, and small bodies beyond the orbit of Neptune.”

These features have not been previously reproduced in all their reality.

To get to this solar system in a box, the team simulated a system like our solar system forming hundreds of times. They started with a gas disk around a young star and assumed bumps in the system’s pressure at specific places that were driven by chemistry: they put pressure bumps at the silicate sublimation line, the water snowline, and the CO snowline. This initial distribution of matter and pressure led to the formation of a ringed system like those we see in Atacama Large Millimeter/submillimeter Array (ALMA) data, and that disk evolved into what we see in our solar system.

More research will be needed to see if this system holds up for other kinds of star systems, but it is a major step forward to be able to get things as simple as “Why isn’t the Earth bigger?” and “Why is the asteroid belt where it is?” to come out of the physics instead of just being the truth about our solar system that lacks cause.

More Information

Rice University press release

“Planetesimal rings as the cause of the Solar System’s planetary architecture,” Andre Izidoro et al., 2021 December 30, Nature Astronomy