[Physics Class Notes] on Solar Nebula Pdf for Exam

Solar Nebula is a large disc-shaped cloud of gas and dust from which planets, the sun, and other bodies of a solar system are formed.

The word “nebula” is a Latin word for “cloud.” The solar nebula was a twisting, flattened disk of gas and dust from which the solar system originated ~ 4.6 Ga ago, where Nebulae are made of residue and gases – hydrogen and helium. The residue and gases in a cloud are extremely fanned out, however, gravity can gradually pull together the bunches of residue and gas.

What will You Learn Here?

On this page, you will learn about the nebula solar system and the nebular theory of formation of our solar system.

What is a Solar Nebula?

Firstly, let’s understand what nebula is.

A nebula is an interstellar dust cloud of hydrogen, helium, and other ionized gases. 

Initially, the term was utilized to portray any diffused astronomical object, including galaxies past the Milky Way. 

The Andromeda Galaxy, for example, was once alluded to as the Andromeda Nebula before the real essence of worlds was affirmed in the mid-twentieth century by Vesto Slipher, Edwin Hubble, and others.

Define Solar Nebula:

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Solar nebula is a gaseous cloud from which, in the purported nebular hypothesis of the source of the solar system, the Sun is formed by condensation.

Development of Nebular Hypothesis

The Nebular hypothesis was developed by a German Philosopher and one of the core Enlightenment thinkers named Immanuel Kant.

Thereafter, he published his work in his Allgemeine Naturgeschichte and Theorie des Himmels, (i.e., the Universal Natural History and Theory of the Heavens), in the year 1755. Later, this theory was modified by Pierre Laplace in 1796.

So, do you know the nebular theory of formation of our solar system? If not, let’s understand this with the help of nebular hypothesis theory.

Solar Nebular Model 

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The development and upgrading in the Solar System started about 4.57 billion years prior with the gravitational breakdown of a little piece of a giant molecular cloud.

The greater part of the falling mass gathered in the middle, forming the Sun, while the rest flattened into a protoplanetary disk out of which the planets, moons, space rocks, and other little Solar System bodies framed. 

This model, known as the nebular hypothesis, was first evolved in the 18-century by Emanuel Swedenborg, Immanuel Kant, and Pierre-Simon Laplace.

Nebular Hypothesis Theory

In 1755, the German philosopher Immanuel Kant suggested that a nebula in a gradual rotation is slowly pulled together by its own gravitational force and flattened into a swirling disk that gave birth to the Sun and planets. 

During the late 19th century the Kant-Laplace views were unsupported by the British physicist James Clerk Maxwell, who showed that, if all the matter contained in the familiar planets had once been diffused around the Sun in the form of a disk, the shearing forces of differential rotation/twisting would have obstructed the condensation of individual planets.

Was Nebula Hypothesis a Failure?

For quite a few years, most astronomers supported the presumed collision theory, wherein planets were considered to have formed because of a close approach to the Sun by another star.

Protests have been raised to the theory of collisions, which are more persuasive than those to the Nebular hypothesis, particularly since it was changed during the 1940s.

The masses of the original planets were thought to be greater than in the prior version of the theory, and the obvious distinction in momentum was ascribed to the magnetic forces associating the Sun and the planets.

Hence, the nebular hypothesis consequently became the predominant theory of the inception of the solar system.

What is Nebula Hypothesis?

The nebular hypothesis is the most acknowledged model in the field of cosmogony to explain the formation and evolution of the Solar System, now, let’s get insight into the nebular model:

This theory suggests that our solar system is made up of gas and dust orbiting the Sun. 

According to the nebular theory, stars form in massive and dense clouds of molecular hydrogen – giant molecular clouds or GMC. 

These giant clouds are gravitationally precarious, and matter combines inside them to more modest denser clumps, which at that point rotate, collapse, and form stars.

Star development is an intricate cycle, which consistently creates a vaporous protoplanetary circle around the youthful star. This cycle may prompt planet development, which is an uncovered actuality up until now.

Now, let’s understand the Nebular theory of formation of our solar system through the Nebula Model:

Nebular Theory of Formation of our Solar System

The below diagram shows the formation of our solar system, i.e., Nebular Model:

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First Step: The dust particles get pulled by a self-gravitational force which then condenses to form a cloud.

Second Step: The clouds so formed are gravitationally unstable, so the conservation of angular momentum on these compresses and reshapes the cloud into a disk. Therefore, the disk starts rotating about its axis of rotation.

Third Step: Now, a central mass forms inside the rotating disk. This central mass is the proto-sun. 

Fourth Step: A centrifugal force balances the gravitational forces and a ring forms. Henceforth, a ring forms a planet.

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Point to Note:

According to the Nebular Hypothesis, the formation of planetary systems is assumed to be an innate result of star formation like the Sun. however, the sun-like star usually takes around 10⁶ years to form, with the protoplanetary disk evolving into a planetary system over the next 10-100 million years.