Question

What are the evolutionary stages of a Sun-like star? Explain the last stage.

Answer 1

Hint
Our Sun is a G-type main-sequence star, better known as a yellow dwarf. The evolution process for these goes like any other main-sequence star starting with a stellar nebula and ending with the formation of a white dwarf.

Complete step by step answer
Majority of the stars in quantity in our universe are the main-sequence star, including our Sun. The Sun is more precisely a G-type star because of its G-V spectral lines.
The birth of a star starts from the formation of a stellar nebula. These are gas clouds consisting of hydrogen, helium, and space –dust. The gas and dust collapse into each other due to gravitational attraction, and the pressure in the core makes the material heat up. As the core keeps getting hotter, a point is reached when fusion starts and a star is born.
As the star comes into existence, it keeps on thriving by converting hydrogen to helium in its core by the process of nuclear fusion. But there comes a time when the star runs out of this fuel, and that is when a Red Giant is formed. The Red Giant survives as long as it has helium to keep it going, but in a million years or so this source of energy also gets exhausted and helium starts converting to carbon.
The giant eventually blows off its outer layers and these give rise to a Planetary nebula. This astronomical object has a typical life of about 10,000 years. As the star becomes smaller in size by shedding its layers, only the hot core remains in the end. This concludes the last stage of evolution of the star and is known as a white dwarf. These are only formed when the mass of the remaining core is about 8 to 10 solar masses. Oxygen and carbon are the most abundant elements found in this stage.

Note
The first-ever white dwarf was discovered by Alvan Clark in 1862. It was a star named Sirius B. White dwarfs are called so because the first few that were observed exhibited white apparent light. Our Sun is bound to become a white dwarf, but this stage is another billion years away.