The Sun is a highly unique star as it is located at the center of the Solar System. Generally, it is white in color (though it appears yellow when seen from earth). Its yellow-green radiation earns it the designation of a yellow star. In terms of size, it has a diameter of approximately 865,000 miles. This roughly covers the diameter of 109 earths. Mass-wise, it takes up about 99 percent of the entire Solar System mass. Out of that 99 percent, hydrogen makes up three quarter while helium occupies the remaining amount.
Before we look into life cycle of the sun, it helps to understand stars. Stars are basically born in nebulae. As massive clouds of gas and dust collapse due to gravitational forces, protostars (young stars) are formed. Further collapse produce sequence stars. Naturally, stars expand in proportion with age. The core contracts as it eventually runs out of gases (hydrogen and helium). This causes it to become less bright. Depending on its original mass, it can either become a neutron star, white dwarf, or black hole. Sun life cycle is highly similar the previous description.
The Sun begins with the shrinkage of large-enough gas cloud. Nuclear fusion then occurs when density and temperature rises. Subsequently, hydrogen is converted to helium and the burning of hydrogen halts the shrinking. At this particular point, Sun is established and this is also the current state of this star. It is worth noting that the hydrogen gas eventually burns out (after billions of years) and the star begins to burn helium. At this stage, it is known as a red giant. The star shrinks every time it runs out of fuel. When helium gas eventually runs out, the life cycle of the sun is nearing its end. As layers are shed, the core becomes a dense “white dwarf”. Soon, it ends up as a dead star (final state of star).
Sun life cycle is an interesting topic because not many people understand how it’s formed or when it’ll die. There are many myths surrounding the existence and death of Sun, but it helps to uncover the truth.