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Debate Heats Up Over Solar System's Formation Order

10/13/2025

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Summary

Story summary

Planetary scientists remain divided over the solar system’s formation order, which began about 4.6 billion years ago.
The accretion theory holds that gas giants formed first, shaping early planetary development.
A competing streaming instability model proposes a different sequence for planet formation.
Planetary scientist Cauê Borlina argues that terrestrial planets may have formed first, causing a chaotic buildup of gas giants.

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Story summary

Planetary scientists remain divided over the solar system’s formation order, which began about 4.6 billion years ago.
The accretion theory holds that gas giants formed first, shaping early planetary development.
A competing streaming instability model proposes a different sequence for planet formation.
Planetary scientist Cauê Borlina argues that terrestrial planets may have formed first, causing a chaotic buildup of gas giants.