Over the past three decades, computer models of planetary system formation have gone from fairly crude representations to sophisticated simulations using thousands of different starting points.
A paper presented at the Origins 2026 conference in Paris details innovative simulations of how our solar system might have formed without making assumptions about the planetary architecture with which we are so familiar.
In his paper, Nader Haghighipour, a planetary scientist at the University of Hawaii in Manoa, argued that his models, unlike previous models, incorporate many completely random starting points and, in turn, let physics drive the models’ ultimate evolution. As a result, these new models are much more complete and allow physics to dictate their outcomes.
“After about 30 years of doing terrestrial planet formation in one specific way, we have reached a point where we realized that the modeling we have done in the past has many limitations and can’t be pushed any further,” Haghighipour said.
“The most viable environment for the formation of habitable planets, one that emerges organically from the evolution of a stellar nebula and is free from any specific assumption, is a protoplanetary disk with a non-uniform distribution of solid material,” Haghighipour writes in his Origins conference paper.
“We have carried out more than 1,000 simulations of the late stage of terrestrial planet formation for a variety of distributions of planetesimals and planetary embryos,” he writes.
A random start
As Haghighipour points out, no one knows our solar system’s precise starting point or how random objects of different sizes were distributed in the initial protoplanetary disk.
“So, we had to go back to the beginning and start from scratch, letting the physics of planet formation take over and take us forward,” Haghighipour says. “That is, without accommodating what we already know about our solar system.”
Haghighipour and colleagues found that the formation of Earth at one Earth-sun distance (or astronomical unit) is a natural outcome of the evolution of our solar system.
“We find that Venus appears about 28% of the time and maintains its orbit, sometimes in the habitable zone of the stars, sometimes slightly outside,” Haghighipour says. “Mars appears a number of times as a small object in the vicinity of the current orbit of Mars.”
Haghighipour and colleagues’ models then simulated these hypothetical planetary bodies’ interactions with one another. Previously, such simulations would sometimes take six to eight months to run; now they can be done within six to eight weeks on current laptop computers.
Tiny details can make a huge difference.
Even a small variation in initial conditions can have a great impact on the final product of a given solar system, Haghighipour says.
An eternal puzzle?
“After life originated (we don’t know how and will never know), life developed branches and bifurcated so that it could find a way to stay in sync with Earth’s evolution,” Haghighipour says.
As for extrasolar Earths?
Given the commonality of Earth-sized planets (including small super-earths) in the habitable zones of solar-type stars, it would be completely logical to consider that Earthly life is common, Haghighipour says.
But can we detect life on planets in other solar systems?
“Finding life on other planets is a very complicated thing; our technology is not at that level,” Haghighipour says. “But this type of study will enable us to understand the characteristics of a planet like Earth and the physical processes that went into its formation and how it became habitable.”
The bottom line?
“There is no reason to believe that our Earth is a fluke,” Haghighipour says.
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New solar system models show Earth is no fluke (2026, August 21)
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