ASTR-301 Lessons

Professor Gagarina enters the room, levitating a large, many armed object ahead of her.  She places it carefully on her desk and waves her wand, illuminating the dark classroom.  There on her desk, ticking gently as the various arms move, is an intricate orrery showing the position of our solar system’s eight planets around a glowing, amber Sun.  On the walls are several brightly colored posters with swirling colors and otherworldly shapes.

Good evening, class.  You see before me a model of our solar system as it is now.  Today we are going to learn about where it came from.  The history of the solar system is a very long one, while our own is quite short.  Historians speak in terms of thousands of years, the rise and fall of civilizations, and many great changes that our world has undergone, but the history of our Earth is tied to the history of the solar system.  Our shared history, though, is measured in billions of years, where great changes can happen slowly or with extreme explosive force.  Understanding these changes is the key to understanding ourselves, our planet, and our magic.

A Whole Lot of Nothing

Five billion years ago, the place in the universe we now occupy looked much emptier.  Instead of the many planets and moons and our Sun, there was nothing but clouds of gases, ice, and dust.  There exists very little energy or activity in pre-solar clouds because they have very little density, meaning that elements and particles rarely interact, and therefore such clouds contain only traces of magic.  These clouds may have stayed together as they were with no change, were it not for a catastrophic stellar event in nearby space.  

                                                    Stars forming in the Orion Nebula

Stars, at their heart, generate light, heat, energy, and magic through nuclear fusion.  As a star begins to use up its main fuel source the center becomes hotter and heavier while the outer edges of the star expand outward, consuming what fuel remains as rapidly as possible.  Eventually the core of the star becomes so hot it starts consuming itself at a massive rate, increasing the temperature, magic, and energy released so quickly that the star explodes.  This explosion, known as a supernova, distributes energy and magic far further than the star could manage during its lifetime.

                                                          Crab Nebula, the result of a supernova

Both of these pictures depict the same type of celestial object.  The brightly lit clouds of gas, dust, and other minute matter are called nebulas, which is Latin for cloud.  There are several different types of nebula which can be divided into two categories: those that exist before stars are formed and those that exist afterward.  The nebula that our solar system came from was a pre-solar nebula; characterized by its high total mass and lack of energy, there is little magic in these clouds.  Nebulas generated after the death of stars, however, contain vast amounts of magic.  Dying stars, themselves generators of magic, seed other worlds, including our solar system, when they die.

Out of the Ashes

About four and a half billion years ago, the pressure wave resulting from a supernova close to the clouds of gas and dust in our space generated more concentrated regions in the clouds.  The extra concentrated weight caused the cloud to generate areas of high mass which collapsed and began to form more solid masses under their own weight.

Our Sun was formed from the largest of these masses: hydrogen, helium, and the magical energy spread from the dying star came together at the heart of the cloud.  Gravity and mass pulled the material inwards, creating enough heat and pressure to form a new star.  Over a period of about fifty million years the center of this star became much denser as gravity pulled material towards the center.  Eventually the heat was great enough to ignite nuclear fusion in the core and our Sun was born.  The Sun at this time burned more fiercely and more chaotically than more stable, older stars.  The variations in pressure, heat, and the amount of matter being pulled into the center of the star lead to the generation of solar winds consisting of high energy particles.  These particles, ejected from the sun at high speeds, spread even more magic, in the form of energy, to the materials that would make up our planet and the rest of our solar system.  Vast amounts of high energy particles and magic also consumed or blew away most of the cloud surrounding the new star.

Smaller bodies formed from the remaining magical energy and the material surrounding the new Sun to become planets.  Rocky planets formed closest to the Sun, and 200,000 years later there were several massive, solid planets that would become the four inner planets of our solar system.  Further from the Sun there is less light and heat, which allowed the various ices and other matter to come together to form solid masses.  The elements that made up these ices are much more common in the universe and these masses were able to grow very large.  The gravitational pull from these objects allowed them to gather large amounts of the remaining gases around them, especially hydrogen and helium, which are the most common elements in space.  These are the gas giants like Saturn and Jupiter, which formed about three million years after the Sun.  Uranus and Neptune are very similar in structure, but are thought to have formed much later.  By that time, the solar winds and the vast amounts of magic the young Sun was spewing into the universe had blown away much of the remaining cloud material, leaving much less gas to form part of the two furthest planets, who are known as the ice giants.

                                                  Artistic concept of early Earth

Come Together

Space dust is made up of many different elements, metals, and minerals such as iron, nickel, aluminum, and silicates.  Individual dust grains, spinning around the sun as it formed, attracted more and more grains of dust which gradually formed large spheres, a process known as accretion.  It is during this process that the fundamental elements of everything in our solar system became impregnated with magical energy.  Particles were exposed to magic from the supernova detonation and solar winds and as they came together, mass and magic were concentrated into planets, including Earth.  Once enough mass had been gathered gravity began to press the various grains closer together.  This enormous gravitational force generated two things: pressure and heat.  These forces helped to pull all the various elements and particles in to form the rocky substance of our Earth.

The solar system is finally coming together.  Smaller regions of cloud are collapsing down into objects that populate the once empty region of space with a huge collection of planets and other large bodies.

That will be all for today.  There is a short quiz you will need to complete on the material covered in this lesson.  Next week you will learn how Earth and its seven siblings came to form the solar system we know today.