Science Writing

The Birth of the Solar System

Day 1 of my 28 Day Solar System Writing Challenge.

The birth of our Solar System was a violent affair. Roughly 4.5 billion years ago a cloud of gas drifting in space suddenly began to collapse in on itself.

This was the beginning of our Solar System, our little corner of the Milky Way that we call our own.

This collapse brought most of the hydrogen, helium, and heavy elements into one point in space, and they formed a protostar, the precursor to the Sun that shines on us today.

Spinning at a rapid rate and drawing more and more material into it, the protostar would eventually consume more than 99% of the material that was within the original cloud. The other less than 1% would become the asteroid belt, the planets and the many moons that crowd out solar system.

What caused the collapse of the molecular cloud? The leading theory is that a nearby supernova exploded and forced the cloud together until it began to collapse uncontrollably, but no one truly knows.

After the collapse, the spin of the protostar formed an accretion disc of matter. Over millions of years this disc flattened out due to the angular momentum of the spin, and the matter within, different heavy and light elements, coalesced into an abundance of different celestial bodies.

The birth of the Solar System and planets, from the formation of the accretion disk to the growth of the planets. Source:  Dorofeeva and Makalkin (2004)

But the Solar System didn’t form evenly. Due to the intense heat of the burgeoning Sun, the objects nearest within the accretion disc, namely the first four planets, Mercury, Venus, Earth, and Mars, could only form out of rock and materials capable of surviving the heat and pressure. Further out, where the temperature was far less, gaseous planets and icy moons could form, pulled together by gravity.

This process, from collapse to the accretion disc dissipating to the formation of the planets in their earliest forms, took about one hundred million years.  

An artist depiction of the early solar system Source: NASA

But to say that the Solar System has finished evolving and will remain in its current state forever would be grossly inaccurate. Everything in space is constantly moving and evolving. The Sun churns as it continuously undergoes nuclear fusion, the enormous energy tossed out by the reactions at its core in a constant battle with gravity forcing it to stay together. The planets shift and tilt in their orbits, interacting with one another, their moons and other celestial bodies as they hurtle through space along ever-changing orbits.

This is the first of the 28 articles on the Solar System and is very much an introduction to the topic at hand. I hope you’ll stick around for the other 27 where I will I go into more detail about specific aspects of the incredible corner of space we live in.


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