A new study from Ohio State University suggests that Jupiter-like exoplanets form much earlier than previously believed, challenging long-held models of planet formation. Instead of taking 3 to 5 million years, as once thought, gas giants may emerge within 1 to 2 million years, reshaping our understanding of how planets come to exist in young star systems.
A New Look At Planet Formation
Planets form from protoplanetary disks, swirling clouds of gas and dust surrounding young stars. These disks provide the raw materials needed for planetary growth through a process called accretion—the gradual accumulation of gas and solid particles.
The study, published in The Astrophysical Journal, suggests that gas giant planets must form while the protoplanetary disk is still young and massive.
By analyzing past observations of seven exoplanets and comparing their chemical compositions to Jupiter and Saturn, researchers found that these worlds accumulated massive amounts of solid material at a surprisingly young stage.
This suggests that gas giant planets must begin forming much sooner than scientists previously thought, otherwise, they would not have had access to enough building blocks.
The Problem With Current Planet Formation Models
For years, the dominant theory of gas giant formation has been core accretion—a “bottom-up” process in which small particles gradually merge to create a planetary core, which then gathers gas from its surrounding environment.
However, this method requires time, and previous models estimated that planets the size of Jupiter would take several million years to fully develop.
The new findings challenge this timeline. If Jupiter-like exoplanets form in just 1 to 2 million years, then either accretion happens much faster than we thought, or another mechanism is at play.
One alternative theory is gravitational instability, where a protoplanetary disk fragments under its own gravity, forming planets almost instantly.
What This Means For Our Solar System?
While the study focuses on exoplanets, it also raises new questions about the formation of Jupiter and Saturn. If exoplanets can form this quickly, it’s possible that Jupiter formed much earlier than previously believed.
Scientists have already suspected that Jupiter played a key role in shaping the early solar system, influencing the development of rocky planets like Earth and Mars.
In fact, the migration of Jupiter and Saturn could explain why Mars is so much smaller than Earth and Venus—the two gas giants may have disrupted the supply of planet-building materials in the early solar system. This study reinforces that idea, suggesting that gas giants can shape planetary systems much sooner than expected.
A Race To Refine Planet Formation Theories
Lead author Ji Wang, an assistant professor of astronomy at Ohio State University, believes this discovery forces astronomers to rethink how planets are born.
“These exoplanets formed so early that there was still a large reservoir of metals available,” said Wang. “This is something that the scientific community was not fully prepared for so now they’ll have to scramble to come up with new theories to explain it.”
The study also introduces a new statistical framework to estimate the solid accretion mass of exoplanets, a tool that could help researchers better understand planet formation across different star systems.
