SUN - ITS ORIGIN AND FATE

It is a G-type main-sequence star (G2V, “yellow dwarf”). This lifespan began 4.6 billion years ago, and will continue for another 4.5 – 5.5 billion years.

The Sun is about half way through the most stable part of its life. During past four billion years, it has remained unchanged. This will continue for another four billion years. After that its hydrogen fuel will be exhausted. The various phases of its life cycles are as follows:

The Birth of the Sun:

According to this theory, the Sun and all the planets of our Solar System began as a giant cloud of molecular gas and dust. Then, about 4.57 billion years ago, a passing star, or shock waves from a supernova caused gravitational collapse at the center of the cloud.

From this collapse, dust and gas began to collect into denser regions. As the denser regions pulled in more and more matter, conservation of momentum caused it to begin rotating, while due to increasing pressure it heated up. Most of the material came at the center as a ball, while the rest of the matter flattened out into disk that circled around it. While the ball at the center formed the Sun, the rest of the material formed the protoplanetary disc. Eventually, the Sun became a main-sequence star.

The Main Sequence:

The Sun, is on the main sequence stage , during which nuclear fusion reactions in its core fuse hydrogen into helium which began 4.57 billion years ago.

Core Hydrogen Exhaustion:

After 5.4 billion years, Sun hydrogen will be exhausted in the core. Core will heat up and get denser, causing the Sun to grow in size till orbit’s of Mercury, Venus, and even Earth. It will then enter the Red Giant Branch (RGB) phase .

Final Phase and Death:

Sun will have approximately 120 million years of active life left.

In this phase, the core (full of degenerate helium), will ignite violently in a helium flash. The Sun will then shrink to around 10 times its current size and 50 times its luminosity. It will continue to burn helium in its core until it is exhausted. Now, it will be in its Asymptotic-Giant-Branch (AGB) phase, where it will expand again and become more luminous.

Sun will then become unstable and loose its mass. It will become larger each time and increase its luminosity. Eventually half of the Sun’s current mass will remain and its outer envelope will form a nebula.

The final, core temperature will be over 100,000 K, after which the remaining matter will cool to become a white dwarf. It will take trillions of years to fade it to black.

Ultimate Fate of our Sun:

When Sun ran out of hydrogen fuel, it would consume heavier fuel till nickel .

Then, iron would start to build up in the core of the star. When about 1.38 times the mass of the Sun is iron collected at the core, it would implode, releasing energy.

This energy would destroy everything in the Solar System. The energy might be enough to outshine the galaxy, and a new nebula would be visible from nearby star systems. All that would remain would be a rapidly spinning neutron star, or maybe even a stellar black hole. It will eventually collapse into a white star until it burns itself out.

A rapidly spinning neutron star, or maybe a stellar black hole will be remaining. It will eventually collapse into a white star until it burns itself out.