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KOMPAS.com – Humans live on a planet called Earth. However, Earth is not the only planet in this solar system.
The solar system or universe consists of the stars from the planet Earth, namely the Sun and everything that is bound to it by gravity such as the planets Mercury, Venus, Mars, Jupiter, Saturn, Uranus, and Neptune.
In addition there are also dozens of moons, millions of asteroids, comets, and meteoroids. Outside the solar system there are many more planets and stars.
The Milky Way, this solar system, is just one of the 100 billion galaxies in the universe.
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What is the solar system?
Reported Space, November 10, 2021, the solar system consists of the sun and everything that orbits around it, including planets, moons, asteroids, comets, and meteoroids.
The solar system extends from the sun, past the 4 inner planets, through the Asteroid Belt, and into the Kuiper Belt.
Scientists estimate that the edge of solar system is about 9 billion miles (15 billion kilometers) from the sun.
Beyond the heliopause lies the giant spherical Oort Cloud, which is thought to surround the solar system.
So how did the solar system form?
There are many theories about the formation of the solar system. according to NASA, Our solar system formed about 4.5 billion years ago from dense clouds of interstellar gas and dust.
The cloud collapsed, possibly due to a shock wave from a nearby exploding star, called a supernova.
When this dust cloud collapses, it forms a solar nebula (a spinning, rotating disk of material).
At the center, gravity pulls more material inward. Eventually, the pressure in the nucleus is so great that hydrogen atoms begin to combine and form helium, releasing a huge amount of energy.
Throughout this process, the Milky Way Sun was born and eventually accumulated more than 99 percent of the available matter.
Matter further down the disc also agglomerates. These clumps collide with each other, forming objects that are getting bigger and bigger.
Some of them grow large enough for their gravity and shape them into spheres, planets, dwarf planets, and large moons.
In other cases, planets do not form. The asteroid belt is made up of pieces of the early solar system that could never have come together to form a planet.
The other small pieces that remained became asteroids, comets, meteoroids, and small irregular moons.
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Here are some theories of the formation of the solar system:
Nebula Theory or Fog Theory (Immanuel Kant-1755 and Pierre Simon de Laplace-1796)
Quoted from NASA, The Nebula Theory is a scientific theory of how stars and planets form from molecular clouds and their own gravity.
Most of the matter in the giant molecular clouds that make up our solar system is made up of the hydrogen and helium produced during the big bang.
Meanwhile it was reported Britannica, Kant’s central idea was that the solar system began as a cloud of scattered particles.
As some of these aggregates became larger than others, they grew faster and eventually formed planets.
But his theory did not explain the planets moving around the sun and also did not explain the revolutions of the planet’s satellites.
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Then a step forward was made by Pierre-Simon Laplace of France, about 40 years later.
He was a brilliant mathematician and very successful in the field of celestial mechanics.
The Laplace model begins with the Sun already forming and rotating and its atmosphere expanding beyond the distance at which the farthest planet would have been created.
Without knowing about the source of energy in the stars, Laplace assumed that the Sun would begin to cool as it radiated heat.
Then due to the cooling, the pressure exerted by the gases decreases and the sun contracts.
According to the law of conservation of angular momentum, a decrease in size will be accompanied by an increase in the rotational speed of the Sun.
Centrifugal acceleration will push matter in the atmosphere outward, while gravitational attraction will pull it toward the central mass.
Then when these forces are balanced, a ring of material will remain in the sun’s equatorial plane.
This process will continue through the formation of several concentric rings, each of which will then combine to form a planet.
Similarly, the moons of a planet will come from the rings produced by the planets that make it up.
The Laplace model naturally leads to observations of the planets revolving around the Sun in the same plane and in the same direction as the Sun’s rotation.
Because Laplace’s theory incorporated Kant’s idea of planets merging from dispersed matter, their two approaches were often combined in a single model called the Kant-Laplace nebular hypothesis.
This model of the formation of the solar system was widely accepted for about 100 years.
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Teori Planetesimal (Thomas C. Chamberlin dan Forest R. Moulton-1905)
In the early 20th century, some scientists decided that the flaws in the nebular hypothesis made it untenable.
Thomas Crowder Chamberlin and Forest Ray Moulton developed a new idea, that the planets formed simultaneously, namely by the meeting of the sun with other stars.
The basis of this model is that the solar system began with the Sun, which was a star (but at that time it was not named the Sun).
Then when another star passes very close to the Sun, the material is pulled out. The materials then combine to form planets.
But the weakness of this theory is that the formation of such a solar system is considered very rare, because close encounters of two stars are very rare.
Then in the mid-20th century scientists realized that hot gaseous material released from the star’s atmosphere would simply disappear in space.
Therefore, the basic idea that the solar system could have formed through the confluence of stars is untenable.
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