#main sequence star

I finally drew Sol again haha

An interesting question was posed to me concerning our ability to know the "life" that is left for our very own Sun...

So, if you were to delve into your favorite astronomical reference book, you would discern a number of interesting qualities of our Sun. For example, it is made of hot plasma and is very big in comparison to our minuscule planet. In fact, the diameter of the Sun is about 109 times that of Earth, and the mass of the sun is about 330,000 times more than Earth. Let's think about that in terms of the entire solar system: the Sun accounts for about 99.86% of the mass of the entire solar system. What is it that makes the Sun so heavy? If we broke the Sun down into chemical components, the majority of it (about 75% or so) is made up of our archaic friend hydrogen. The rest is mostly helium, and less than 2% is made of other, trivial elements like oxygen. Our Sun is what is called a main-sequence star which means that it is constantly converting hydrogen into helium through nuclear fusion. This is the mode of energy creation for a star like our's, and is the reason why your skin turns a nice salmon pink if you are of a fair complexion in the summer time and forget to have someone rub sunblock on your back. Now, there are many things to be discussed about our solar partner that I could probably write a nice book discussing phenomena linked to our Sun, but for this post I will deal with the question at hand: How do we know that the Sun simply won't just burn out anytime soon?

My friend asked about this, since we know that stars do not have an infinite lifetime, and we always are seeing beautiful pictures from the Hubble telescope of supernovae and stellar explosions, which does warrant the interesting question of why and when our star will explode! 

Astrophysicists approximate the age of the Sun to be at 4.57 billion years old. How do they know this? Well they approximated this by dating material (via radiometric dating) around the solar system, and by using fancy computer modelling. Right now, our yellow friend is sitting at about the middle of the main-sequence cycle for a star, which means that it is at the middle of this phase of the Sun in which it is converting hydrogen into helium. We figure that the sun is converting 4 billion metric tons of mass into energy every second. That is one badass nuclear fusion reactor. Scientists believe that the Sun has enough mass to fuel this process for about 10 billion years. So right now we have about 5 billion or so years before we should start worrying about the Sun exploding. In 5 billion years, the Sun will become a red giant, and it is believed that this huge version of the Sun will engulf the Earth! So we have only 5 billion years of life left!! What to do in such a short amount of time?

Not so fast! We do not have 5 billion years to worry about the sun exploding however. In reality, we only have about a billion years left of terrestrial life here on Earth. Why?! Because during this main-sequence, the Sun has slowly been getting hotter and more luminous. This means that at a certain point, the Sun will give off too much heat for water to exist on Earth (thus effectively ending all forms of life). So in a mere billion years, we will have to kiss our terrestrial home goodbye. However, I tend to think that we will end up ruining life on this planet way before a billion years passes, what with the threat of nuclear war and not to mention global warming and pollution.

What's going to happen is, very soon, we're going to run out petroleum, and everything depends on petroleum. And there go the school buses. There go the fire engines. The food trucks will come to a halt. This is the end of the world.