Sun

Our Sun is an ordinary star although it is quite large compared to other stars. In terms of “mass”, most stars have less than half the mass of our Sun. You could fit 109 Earths across the Sun. The Romans called the Sun “sol” (as in SOlar).

The Sun is about 70% hydrogen and 28% helium. The Sun converts hydrogen to helium at its core. The Sun is not a solid body like Earth. This accounts for why the outer shell of the Sun rotates around its core. In this way, it sort of behaves like planets that are made of gas. At its poles, it rotates once about every 36 days while at the equator (or mid-line) it rotates about every 25 days. This produces a swirling type effect.

The core of the Sun, or the inner 25% of its radius, is very dense, about 150 denser than water. It is also under a tremendous amount of pressure. Nuclear Fusion is how the hydrogen is converted to helium. When the hydrogen particles fuse to form the helium, a little bit of the mass is left out and released as energy. The energy that is released at the core is called gamma rays. The gamma rays make their way towards the outer shell but on the way, the bounce and are absorbed. By the time the energy reaches the surfaces, it’s mostly just visible light and heat. It takes this energy millions of years to reach the surface.

Surrounding the Sun is an area of space called the corona. It extends millions of miles into space. You can see it clearly when there is a solar eclipse.

A stream of charged particles (mostly electrons and protons) is also spit out. These travel through space and are called Solar Wind. They have a funny effect on electrical devices here on Earth. The output of Solar Wind changes from day to day. On bad days, it can cause power surges in our electrical lines which blows out electrical equipment.

The Sun is about 4.5 billion years old and has consumed about half of the hydrogen at is core. It will continue being the Sun for about 5 billion more years. At that time, it will run out of hydrogen fuel and “burn out” (and be a lot brighter by that time too). It will swell in size and completely swallow the Earth. By that time, Man will have figured out a way to travel through space to other planets or how to build another Sun because once the Sun burns out, life here on Earth will not be able to exist.

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