The Origin of the Solar System

Research PaperScience
Jan 1, 2007

research paper is an academic project that presents a main idea or claim in the form of a thesis statement . The body of this paper expounds on the thesis and supports it using evidence from credible sources . In this sample research paper, the author presents the major theories that attempt to explain the origin of the Solar System.

Since prehistoric times, people have been pondering the origin of the Solar System. In all likelihood, ancient humans gazed up to the night sky and wondered where everything came from or how they are formed. Of course, religion offered explanations regarding the origin of the universe as well as the origin of life . But as science advanced and grew in influence, it also began to formulate more informed theories that attempt to explain where the universe came from such as the Big Bang Theory or how modern humans came about through the evolution of man . In particular, the understanding that the Earth is part of a planetary system now known as the Solar System coupled with knowledge about the workings of the universe has led to multiple theories published throughout the centuries. So, the main question is: where did our Solar System and everything in it come from? There are numerous theories available today, but the three most prominent are the Kant-Laplace nebular hypothesis, the Chamber-Moulton planetesimal hypothesis, and the capture theory.

The Kant-Laplace Nebular Hypothesis

The Kant-Laplace nebular hypothesis derives its name from the German philosopher Immanuel Kant (1724-1804) and the French mathematician Pierre-Simon Laplace (1749-1827). The theory was first developed by Kant, who theorized that the Solar System began as formless clouds of particles. The gravitational pull of these particles caused them to move and collide against each other. Over time, the particles reacted with one other and combined to form larger and larger objects until they became as big as planets (Dyck et al., 2018). Kant’s theory, however, had several limitations. For one, it did not explain why the planets revolve around the Sun in the same direction. Neither did it explain why the planets share a plane. It also did not take into account the existence of non-planetary objects like moons (Chambers & Mitton, 2017).

Laplace eventually developed Kant’s theory by supplementing it with further explanations. Laplace assumed that the Solar System began with the formation of the Sun due to the aggregation of particles in the center of a spinning cloud or nebula. The aggregation of particles led to the increase in heat and pressure until eventually, the particles became the Sun itself. As the Sun was emitting heat, it was also in the process of becoming smaller and cooling down. Two forces are generated here. First, the Sun’s contraction to a smaller size meant that it was also spinning at a faster rate, thus causing centrifugal acceleration that pushed material away. Second, the Sun’s gravitational pull attracted material toward it. These competing forces pushed and pulled the material away and toward the Sun until they eventually established balance. This resulted in concentric rings of material surrounding the Sun’s equator and revolving around it. Over time, the suspended material also combined to form the planets themselves (Buchwald & Fox, 2017).

Laplace’s additions to Kant’s theory helped answer some of the questions that Kant did not address. For one, the formation of the concentric rings of material around the Sun’s equator due to the push and pull forces exerted by the Sun explained why the planets were located in the same plane. For another, Laplace’s work also explained why the planets traveled in the same direction. Laplace’s model also explained why planets have satellites since the same mechanism that supposedly formed the planets around the Sun formed the satellites around the planets. Finally, this model also explained why terrestrial planets like the Earth and Mars are close to the Sun and the gas giants like Jupiter and Saturn are located farther out. The pushing and pulling forces described earlier pushed the lighter particles farther while trapping the heavier particles close to the Sun. However, this expanded theory still did not account for other factors. For instance, this model did not explain the presence of objects like asteroids with unusual orbits (Chambers & Mitton, 2017). But despite these, the model was widely accepted for over a century and remains to this day an important theory regarding the origins of the Solar System.

Chamberlin-Moulton Planetesimal Hypothesis

The second dominant theory is the Chamberlin-Moulton planetesimal hypothesis, which is named after the American geologist Thomas Chrowder Chamberlin (1843-1928) and the American astronomer Forest Ray Moulton (1872-1952). According to this theory, the Solar System was formed due to the passing of a star near the Sun. According to Chamberlin and Moulton, a star passed by the Sun early in the latter’s life. The force of the passing star caused the Sun to eject material from its main body. While the majority of the ejected material was eventually reabsorbed by the Sun, those that remained suspended eventually aggregated to become planetesimals, which are small objects of accreted material, and protoplanets, which are bigger objects developing into planets. Over time, these grew larger to become planets themselves, thus resulting in the formation of the Solar System (Stephenson, 2021; Moulton, 2021).

In a way, the Chamberlin-Moulton planetesimal hypothesis shares many elements with the Kant-Laplace nebular hypothesis. In particular, the accretion of material resulting in the formation of planets and other objects figure prominently in both theories. However, the main difference is the role played by another star. Unlike Kant and Laplace’s theory, Chamberlin and Moulton integrate the role of another star in the formation of the system. Furthermore, the planetesimal hypothesis had not supplanted the nebular hypothesis in terms of acceptance by the scientific community. For instance, the American physicist Lyman Spitzer, who was more familiar with the fundamentals of physics , asserted that material expelled from the sun would not accrete but instead would scatter or continue to travel beyond the confines of the Solar System (Chambers & Mitton, 2017). But regardless of its merits, the Chamberlin-Moulton planetesimal hypothesis remains an important development in humanity’s quest for an explanation of the Solar System’s origin.

Capture Theory

Capture theory is another prominent hypothesis that attempts to explain the origin of the Solar System. This theory was first proposed by British physicist Michael Mark Woolfson (b. 1927) in the 1960s. According to Woolfson, the Solar System may have formed as a result of interaction between the Sun and a protostar, which is a star in its early stage of development. This began with what Woolfson considers as tidal interactions between a passing low-density protostar and the Sun. The Sun’s gravitational pull drew material from the protostar as it passed by, which was made possible due to the aforementioned low density of the young star. Once the material had been pulled out, they settled around the Sun and slowly accumulated to become planets. This process lends the theory its name; the Sun “captured” material from the passing protostar, which in turn became the planets and other objects in the Solar System (Woolfoson, 2014).

Like the Chamberlin-Moulton planetesimal hypothesis, the capture theory integrates some of the elements from preceding theories. Firstly, the capture theory is similar to the Kant-Laplace nebular hypothesis in that it considers accretion, the process by which loose materials coalesce to form planets, as integral to the birth of the Solar System. Secondly, it also features the role of another star as proposed by Chamberlin and Moulton. But the crucial difference is that the capture theory derived material from the protostar whereas the planetesimal hypothesis theorizes that the material came from the Sun itself.


There are many theories that attempt to explain the origins of the Solar System. Three of the more prominent ones are the Kant-Laplace nebular hypothesis, the Chamber-Moulton planetesimal hypothesis, and the capture theory. The nebular hypothesis asserts that the Solar System began as a nebula that slowly formed a star in the center and then moved on to the formation of the planets as a result of the forces exerted by the Sun. The planetesimal hypothesis, on the other hand, claims that a passing star drew material out of the Sun, and this material eventually accumulated around the Sun and became the planets and other objects. Finally, the capture theory also factors in the role of a passing star. But instead of the star causing the Sun to expel material, it claims that the process was the other way around. The Sun captured material from the passing young star, which in turn became the planets and other objects. Each of these theories has its own strengths and weaknesses. It may also be true that none of these theories will ever be considered the definitive explanation. But they are all important in humanity’s attempt to understand where the Solar System came from.

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Buchwald, J. Z. & Fox, R. (2017). The Oxford handbook of the history of physics. Oxford University Press.

Chambers, J. & Mitton, J. (2017). From dust to life: The origin and evolution of our Solar System. Princeton University Press.

Dyck, C., Dahlstrom, D. O., & Wunderlich, F. (2018). Kant and his German contemporaries. Cambridge University Press.

Moulton, F. R. (2021). An introduction to astronomy.

Stephenson, C. A. (2021). Periodic orbits: F. R. Moulton’s quest for a new lunar theory. American Mathematical Society.

Woolfson, M. M. (2014). The formation of the Solar System: Theories old and new. World Scientific.

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