The Formation of The 'So Large' System

By Winnie Jiang

Main Article

When we look up at the night sky, we can see our moon illuminating the night roads. Mercury, Venus, Mars, Jupiter, and Saturn gleaming brightly. And meteor showers visiting our vast solar system in this long history of space. Nevertheless, our solar system has not been like what we now know.

The Solar System was just an enormous dense cloud of gas and dust 4.5 billion years ago at an outer spiral arm of the Milky Way Galaxy. Possibly a nearby exploding star, a Supernova explosion's shockwave caused the cloud to collapse. The shockwave brought gas and dust particles together, and gravity caused the contraction to continue, shrinking the original cloud size.

The center of the cloud was denser than the other parts; hence its gravitational pull was stronger, compressing more molecules, heating itself up, and becoming a protostar. The clouds around it began to spin and flattened themselves out to a disk, later becoming essential components of planetary formation.

Over time, the center of the protostar was dense and hot enough, fueling a nuclear reaction. The nuclear reaction increased the heat released from the star, and the outward pressure from the heat halted the collapse. By now, the star at the center of our solar system, the Sun, is formed.

When the Sun was forming, planets formed also. The particles from the disk of gas and dust orbiting the Sun collide. The gas acts like glue, helping the solid materials to stick together. However, the fast particles will bounce off; the slower ones will stick together. Imagine a snowball fight. If you get struck by a slow snowball, it would likely be stuck on you. Nonetheless, if you are struck by a fast snowball, it would bounce off, and you would likely flinch away from it. Forming larger and larger particles by attracting particles due to gravity. These big materials are called planetesimals. Amidst this chaos, planets began to form. And only a few of those planets would remain.

We now know the remaining planets as Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. Scientists suspect there is the ninth planet similar to the size of Uranus and Neptune, orbiting far beyond Pluto, a dwarf planet in the Kuiper Belt; they named the planet "Planet X."

Many particles left behind from the solar system's formation became the asteroid belt between Mars and Jupiter, the Kuiper Belt, lying beyond the orbit of Neptune, and the Oort Cloud, which lies even beyond the Kuiper Belt, surrounding the solar system as a sphere. The Oort Cloud is also where the Sun's influence ends.

Of course, the order of the Solar System is not this simple. It is divided into the inner solar system and the outer solar system with the asteroid belt in between. The inner solar system includes Mercury, Venus, Earth, and Mars. The inner planets are dense, rocky, mostly similar in size and composition, have no rings, and do not have many moons. This is because the "Big Daddy," the Sun, it's gravitational pull denser materials towards itself, and the lighter particles like gas can escape more easily. Mercury and Venus have no moons, Earth has only one moon, and Mars has two. However, few asteroids visit the inner planets and become their moon temporarily. Earth had a mini-moon called 2020 CD₃, and it was discovered on February 15, 2020. It orbited Earth for as long as 380 days.

The outer planets are Jupiter, Saturn, Uranus, and Neptune. The outer planets are enormous, have a composition of liquid and gasses, have numerous moons, and all have rings; also, because of their thick gaseous outer layers, they are all gas giants, also called the Jovian planets.

In fact, our solar system is unique to other planetary systems in some ways. Many exoplanets are gas giants close to their stars; however, our jovian planets are located in the outer solar system and are extremely cold.

Scientists suspect Jupiter, one of the Jovian planets, formed early in the solar system's formation and had traveled back and forth. This scenario is called "The Grand Tack," published in 2011 in nature. It said that the Sun's gas swept Jupiter inward, as close to the Sun as Mars is now. And Saturn, a newborn planet, was swept in also. However, Saturn's gravitational pull was able to stop Jupiter from moving even closer to the Sun. So the two planets stayed there and absorbed materials in that region. When most gasses were used or flung away, Jupiter was free to move back from the Sun's swirling gas and settled where it is today. This migration caused Mars' small mass and the significant difference in composition of the asteroid belt. The terrestrial planets are also said to be formed after Jupiter's adventure from a messy planetesimal disk Jupiter left behind. Their rocky composition and small mass compared to the gas giants are also caused by the Grand Tack.

The Solar System is a wondrous thing, from its formation, to what it is now. In the grand scheme of things, our Solar System was able to form, the Earth was able to form, and we are given the opportunity to live in this miraculous place written by the Universe. We can always raise our heads for a few seconds, and appreciate the world after the chaos of the formation of the Solar System that we now live in.

Vocabulary

Solar System:

The collection of eight planets and their moons in orbit around the sun, together with smaller bodies in the form of asteroids, meteoroids, and comets. The planets of the solar system are (in order of distance from the sun) Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. (Oxford Language and Google)

Star:

A sphere of gas held together by its own gravity. (NASA)

Planet:

A celestial body that […] is in orbit around the Sun […] has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and […] has cleared the neighbourhood around its orbit. (NASA)

Milky Way Galaxy:

The galaxy of which the sun and the solar system are a part and which contains the myriads of stars that create the light of the Milky Way. (Merriam-Webster)

Planetary System:

A set of asteroids, planets, and other non-stellar objects orbiting around a star or a star system bound by gravity. The Solar System is a Planetary System.

Supernova:

The explosion of a star. It is the largest explosion that takes place in space. (NASA)

Gravity:

The force that attracts a body toward the center of the earth, or toward any other physical body having mass. (Oxford Language and Google)

Protostar:

A cloud of gas and dust in space believed to develop into a star. (Merriam-Webster)

Nuclear Formation:

The nuclei of two atoms combine to create a new atom. Most commonly, in the core of a star, two hydrogen atoms fuse to become a helium atom. (Lumen Learning)

Planetesimals:

Any of numerous small celestial bodies that may have existed at an early stage of the development of (a planetary) system. (Merriam-Webster)

Asteroid Belt:

Particles left behind from the solar system's formation became the asteroid belt between Mars and Jupiter.

Kuiper Belt:

An asteroid belt that lies beyond the orbit of Neptune.

Oort Cloud:

A sphere of asteroids that lies beyond the Kuiper Belt, it is also where the Sun's influence ends.

The inner solar system: Includes Mercury, Venus, Earth, Mars, and everything that lies between the Sun and the asteroid belt. The inner planets are dense, rocky, mostly similar in size and composition, have no rings, and do not have many moons.

The outer solar system: Includes Jupiter, Saturn, Uranus, Neptune, and everything that lies between the asteroid belt and the Oort Cloud. The outer planets are enormous, have a composition of liquid and gasses, have numerous moons, and all have rings, they are also called the “Gas Giants.”

The Grand Tack: A scenario where Jupiter and Saturn migrated to the inner solar system where Mars now is and moved out to the outer solar system once again.