Main Sequence Star: Our Sun’s Thermonuclear Reaction

How did the sun come into existence?

The sun is mostly hydrogen (74%) and helium (25%). It started with hydrogen bundling together and rotating. Eventually, four hydrogen atoms connect with four electrons to create one helium atom through heat.

If you look at hydrogen on the periodic table, four individual hydrogen atoms have more mass than one helium atom. According to Einstein, you can’t lose mass. But you can convert mass to energy. Stars are a thermonuclear reaction where four hydrogen atoms are put together into helium.

In our case, our Sun releases the energy that we see as sunlight on Earth. So it burns hydrogen into helium and releases energy. Typically, stars go through this “main sequence” for about 95% of its life. So for most of our sun’s life, it’s releasing energy as sunlight through thermonuclear reactions.

How much longer will the sun’s fire burn for?

Just like any fire, eventually fires burn out. Similarly, stars all have life spans. Heavyweight stars have the most fuel, but burns it at the fastest rate.

The smallest stars live the longest at a minimum of 50 billion years. If you compare this to the universe, it’s only 13 billion years old.

Our Sun is 1 SM and is classified as a lightweight. In the lightweight category, this means that it has a life expectancy of about 10 billion years.

Currently, we’re into 5 billion years for our Sun. It’s at the middle age of its life and has about 4 billion more years. It won’t become a supernova and will collapse into a white dwarf.