How did our cosmic home—the solar system— fashion itself? This is a tale of billions of years. Put another way, begin with a huge whirling cloud of gas and dust. Consider that clouds whirling around aimlessly and shapelessly through space. About 4.6 billion years ago, this large cloud collapsed. It contracted, heating up, and eventually it became what we know today as the Sun. Out of leftover material, what would be ourselves—the planets, moons, asteroids, and comets were formed.
Our solar system formed from a tremendously vast interstellar cloud—the solar nebula. This tremendous cloud of dust, hydrogen, and other gases collapsed under its own self-gravity. This may have been triggered by a collisional shock wave caused by a nearby supernova—that is, an exploding star. As the cloud collapsed, it began to spin faster and faster, much like a figure skater does when she pulls in her arms to generate increased momentum to spin more quickly. The core became incredibly hot and dense and formed the Sun. “About 99.9% of the material fell into the middle of the cloud and became the Sun,” says researcher Tim Gregory. The remaining 0.1% of the matter continued in orbit around the Sun and started flattening into a flat, rotating disk known as the protoplanetary disk. Over time, this disk cooled down and condensed; the first solids formed and clumped together.
These clumps grew bigger and bigger, sweeping up all the leftover dust until they became planets. High temperatures near the Sun took up rocky planets like Mercury, Venus, Earth, and Mars. Farther along, where it was cool enough, gas and ice giants formed—Jupiter, Saturn, Uranus, and Neptune. A lot of understanding about the timing of our solar system comes from piecing together an ancient, scattered puzzle. Let us break this down: 4.6 billion years ago: collapse begins in part of the interstellar solar nebula, forming eventually the Sun.
4.55 billion years ago: Nuclear fusion in the Sun starts fusing hydrogen into helium, radiating light and warmth.
4.5 billion years ago: The Earth and other rocky planets start forming. A Mars-sized object smashes into Earth, resulting in the Moon being created. 3.8 to 3.5 billion years ago Life on Earth as we knew it begins, the origin of everything that will lead, eventually, to us. It was, however a process of formation that left over many of the small bodies that didn’t become planets.
Among them are the asteroids most of them are located in the asteroid belt between the paths of Mars and Jupiter.
One of these rocks melted early in their history to form iron cores and rocky mantles. Those that didn’t melt are called chondrites, and they remain as pristine samples of the original materials that made up the solar system. Says Gregory, “Chondrites are the first solids that formed in the solar system.”. Now, let us talk about moons. It also contains hundreds of moons and they’re all planetary satellites. As might be expected, Jupiter again comes first, with 95 moons, and Saturn is second, with 146. Even the dwarf planet Pluto has five moons. And few of the planets without accompanying satellites are Venus. It does, however, have a quasi-satellite called Zoozve. It also holds much more than the eight planets with their moons. Beyond Neptune, there exists a ring of icy bodies, among them the dwarf planet Pluto, known as the Kuiper Belt. At even further reach lies the Oort Cloud—a huge shell of icy debris supposedly at the source of long-period comets. The Oort Cloud marks the outer boundary of the Sun’s gravitational influence. Things become interesting when one learns that two launched NASA spacecraft do exist, Voyager 1 and Voyager 2, launched in 1977 at the edge of our solar system and shall enter interstellar space. Voyager 1 did so in 2012, followed by Voyager 2 in 2018. However, for them to fully exit the Oort Cloud will take thousands of years more.
Our solar system wasn’t made overnight. Rather, a list of long-drawn-out processes leads to the shaping of these well-known celestial bodies. Events which formed our solar system can then be summarized in the following crucial ways:
- The forming of the Sun from the collapse of the solar nebula,
- Forming a protoplanetary disk from which the planets formed, and
- Gravitational accumulation of materials to form the terrestrial and gas giant planets
Continuing the process of moon, asteroid, and comet formation and evolution. So next time you face upwards towards the night sky then, remember that each star and planet has a story unfolding for its birth, just our solar system has been. It is not a moving-stop journey against learning, understanding not just where we came from—our place in the vast cosmos.
