The Sun

Keywords

The Sun, protostar, yellow star, 4.6 billion years, hydrogen fusion, helium, carbon, core, red giant, white dwarf, gravitational pressure, thermal pressure, hydrostatic equilibrium, main sequence, helical model.

Introduction

The Sun is a star. Like the ones you see in the sky above at night. Each star has a life cycle, and our Sun is about halfway through it's own life cycle. The Sun is a giant ball of plasma, hydrogen and helium are the most abundant of chemicals that make it what it is. The Sun is kept together by two types of pressure - gravitational pressure, where things are being pulled together, and thermal pressure - this is generated by nuclear fusion.

Okay, so how was it made?

Gravity. Shall I say it again? Gravity. It is how most things in the universe have been made. At least celestial beings and objects in space. The Sun is no different. A giant cloud of hydrogen that contained remnants of dead stars from the past collapsed. It could have collapsed by a nearby explosion of supernova, but this is unclear.

Once the gases collapsed, over time it became more dense and started to heat up. Whilst this was happening, a solid core formed in the centre of the star, and this was very much hotter than the rest of it. This is called a protostar, which although it is very hot, it's not quite hot enough to start hydrogen fusion. If the mass of the Sun was slightly less than it was at this point, it would have been like having a still-birth, and nothing much else would have happened. It's quite common in the universe that this happens.

Interesting fact: the Sun holds about 99.86% of the entire mass of the Solar System, but is still just a mass of gas and has no solid surface.

Thankfully, there was a little more mass in the Sun, and gravitational collapse occurred. The continual compression and gravitational pull created more and more heat, which resulted in...

Hydrogen Fusion Begins!

The Sun has lots and lots (like, millions) of hydrogen atoms floating around each other. What happens when you superheat these atoms? Fusion. Nuclear fusion, to be precise. They moulded together and formed helium, which in turn created more and more heat. This is the main source of the Sun's fusion furnace. It continues this process to this day. The creation of thermal pressure (generated by the nuclear fusion of hydrogen), and the gravitational pressure both neutralised themselves against each other, and boom - you have hydrostatic equilibrium.

This phase of a star is called the "Main Sequence", and the Sun has been in this phase for some 4.6 billion (4,600 million) years. It will continue to do this for some millions of years to come.

How the Solar System was Created

So, in effect, from the remnants of an old star that ended life, to another star that became our Sun. This was how the Solar System was created, with a disk of swirling matter around it.

But that's not the only thing we know. From early astronomy, where thinking was generally that the Earth was the middle point and everything (including the Sun) rotated around it, to the Sun becoming the middle point, and everything rotates around that, we have now figured that the Sun is also moving along, with everything that rotates around it, moving forward (or backward, for those of you being pedantic) with it.

The Sun is in a helical model. There is an image in the resources that show this.

What Happens in the Future?

Well, at some point, that finite resource of hydrogen will run out, and when it does, the Sun will expand. It will turn into a red giant star, much like Betelgeuse in the constellation Orion, and when it does, it will swallow Mercury and Venus. Temperatures on Earth will become so hot it will become uninhabitable. Even the orbits of the remaining planets will change as a result of the change in dynamic of the Sun.

The red giant Sun will compress further, and turn helium into carbon. Once again, the supply of helium will run out, and then there will be no further generation of heat, and no other elements will be able to be heated. Eventually, the red giant will turn into a white dwarf star, and its energy will slowly radiate over eternity and be left to die.

This is not due to happen for abosolute millions of years. Long after you or I have passed on. But, in our quest, we seek out new lives and civilisations (to quote Star Trek), in the form of exoplanets that litter the universe. At the moment, we realise that we are the only "humanoid" creatures to live, and that we are the only living planet in the universe, but millions of years may pass, and we may find new species of creatures or organisms that we can live with, adapt to or even move on to. There are already plans to make a settlement on Mars, so who knows?