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Nebular Theory Might Explain How Our Solar System Formed
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Our solar system contains the sun, inner rocky planets, the gas giants , or the outer planets, and other celestial bodies, but how they all formed is something that scientists have debated over time.
The nebular theory , also known as nebular hypothesis , presents one explanation of how the solar system formed. Pierre-Simon, Marquis de Laplace proposed the theory in 1796, stating that solar systems originate from vast clouds of gas and dust, known as solar nebula, within interstellar space.
Learn more about this solar system formation theory and some of the criticism it faced.
What Is the Nebular Theory?
Criticisms of the nebular theory, solar nebular disk model.
Laplace said the material from which the solar system and Earth derived was once a slowly rotating cloud, or nebula, of extremely hot gas. The gas cooled and the nebula began to shrink. As the nebula became smaller, it rotated more rapidly, becoming somewhat flattened at the poles.
A combination of centrifugal force, produced by the nebula's rotation, and gravitational force, from the mass of the nebula, left behind rings of gas as the nebula shrank. These rings condensed into planets and their satellites, while the remaining part of the nebula formed the sun.
The planet formation hypothesis, widely accepted for about a hundred years, has several serious flaws. The most serious concern is the speed of rotation of the sun.
When calculated mathematically on the basis of the known orbital momentum, of the planets, the nebular hypothesis predicts that the sun must rotate about 50 times more rapidly than it actually does. There is also some doubt that the rings pictured by Laplace would ever condense into planets.
In the early 20th century, scientists rejected the nebular hypothesis for the planetesimal hypothesis, which proposes that planets formed from material drawn out of the sun. This theory, too, proved unsatisfactory.
Later theories have revived the concept of a nebular origin for the planets. An educational NASA website states: "You might have heard before that a cloud of gas and dust in space is also called a 'nebula,' so the scientific theory for how stars and planets form from molecular clouds is also sometimes called the Nebular Theory. Nebular Theory tells us that a process known as 'gravitational contraction' occurred, causing parts of the cloud to clump together, which would allow for the Sun and planets to form from it."
Victor Safronov , a Russian astronomer, helped lay the groundwork for the modern understanding of the Solar Nebular Disk Model. His work, particularly in the 1960s and 1970s, was instrumental in shaping our comprehension of how planets form from a protoplanetary disk.
At a time when others did not want to focus on the planetary formation process, Safronov used math to try to explain how the giant planets, inner planets and more came to be. A decade after his research, he published a book presenting his work.
George Wetherill's research also contributed to this area, specifically on the dynamics of planetesimal growth and planetary accretion.
This article was updated in conjunction with AI technology, then fact-checked and edited by a HowStuffWorks editor.
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44 The Nebular Theory
A protostar is an object in which no nuclear fusion has occurred, unlike a star that is undergoing nuclear fusion. A protostar becomes a star when nuclear fusion begins. Most likely the next step was that the nebula flattened into a disk called the Protoplanetary Disk ; planets eventually formed from and in this disk.
Three processes occurred with the nebular collapse:
- Temperatures continued to increase
- The solar nebula spun faster and faster
- The solar nebula disk flattened
The orderly motions of the solar system today are a direct result of the solar system’s beginnings in a spinning, flattened cloud of gas and dust.
Introduction to Astronomy Copyright © by Lumen Learning is licensed under a Creative Commons Attribution 4.0 International License , except where otherwise noted.
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Observed features any origin model of the solar system/planets must explain
Atoms in your body, collapsing clouds of gas and dust in nebular hypothesis, the spinning nebula flattens, condensation of protosun and protoplanets, the composition of the sun, the two classes of planets, etc. explained by the nebula hypothesis:, evidence for the nebular hypothesis.
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