How solar system formed
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The Formation of the Solar System
Introduction to Solar System Formation
The formation of the solar system began approximately 4.56 billion years ago, a process that has been pieced together through the study of meteorites, the current structure of the solar system, and observations of planet-forming systems around young stars 12. This article synthesizes the key stages and mechanisms involved in the formation of our solar system.
Collapse of the Interstellar Cloud
The solar system's formation started with the gravitational collapse of a region within a molecular cloud, leading to the creation of a protoplanetary disk around a newly formed Sun . This collapse was likely triggered by external forces such as a nearby supernova, which injected short-lived radionuclides like 60Fe into the nascent solar system 46.
Formation of the Protoplanetary Disk
As the interstellar cloud collapsed, it formed a rotating disk of gas and dust around the young Sun. This disk, known as the solar nebula, was the birthplace of planetesimals—small bodies that would eventually coalesce to form planets . The presence of high-temperature grains far from the Sun suggests significant mass transport within the disk, possibly driven by bi-polar outflows and turbulent diffusion .
Differentiation of Inner and Outer Solar System
The solar system's formation involved the differentiation of materials into two distinct reservoirs, separated by the migration of the snow line—the boundary between regions containing water vapor and solid ice 59. This migration created two populations of planetesimals, which later collided and merged to form the planets. This process explains the compositional differences between the inner rocky planets and the outer gas giants 59.
Role of Stellar Clusters
The solar system likely formed within a star cluster containing at least 1000 stars, which influenced its chemical composition and the orbital parameters of its bodies . The high density of such clusters could have led to significant gravitational interactions, shaping the early solar system's structure . However, the solar system's high circularity suggests it formed in a less dense, "leaky" cluster rather than a dense starburst cluster .
Meteorite Evidence and Planet Formation
Meteorites provide crucial evidence for the solar system's formation. Chondritic meteorites, which formed from the accretion of material in the solar nebula, indicate that the solar nebula dissipated within a few million years . The differentiation of asteroidal-sized bodies occurred within 5 to 15 million years, while the terrestrial planets took around 100 million years to form, incorporating already differentiated bodies .
Supernova Influence and Radionuclides
The discovery of decay products of 60Fe in meteorites suggests that the solar system formed in a region with one or more massive stars that went supernova, injecting newly synthesized radionuclides into the protoplanetary disk . This supernova event likely played a critical role in the solar system's chemical makeup and the presence of short-lived radionuclides 46.
Conclusion
The formation of the solar system was a complex process involving the collapse of an interstellar cloud, the formation of a protoplanetary disk, and the differentiation of materials into distinct reservoirs. Influenced by nearby supernovae and the dynamics of a star cluster, the solar system's evolution was shaped by both internal and external forces. Meteorite evidence and astronomical observations continue to provide valuable insights into this intricate process, helping us understand the origins of our cosmic neighborhood.
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