Universe and Outer space

During this phase, we can see a Star similar to the Sun producing heat and light due to the thermonuclear fusion reaction. It has been estimated that stars spend about 90% of their lifetime in this phase. During this phase, the proportion of helium in its core keeps increasing and loses a very small fraction of its mass. The only visible differences will be a considerable increase in its temperature and luminosity. The Sun’s luminosity is estimated to have increased by about 40% since it reached the main sequence. (The initial mass and the proportion of heavier elements influence the evolution of a star). Nothing spectacular happens during this phase. Massive stars burn out their fuel faster while the lighter ones burn their fuel slowly and can last from tens to hundreds of billions of years.

So let’s keep moving forward in time, till we begin to see signs of expansion at the outer layers of the star. The star is beginning to turn into a Red Giant (This is because, the star runs out of fuel, and the nuclear fusion in the core stops…the core starts contracting under its own gravity…however this heats up the layer just outside the core, initiating fusion of hydrogen to helium…the higher temperatures causes the luminosity to increase manifolds…and the outer layers begin to expand causing the surface temperature to fall considerably and the visible light output shifts towards the Red end of the spectrum).

Its not safe for us to stay close to this star anymore because it is going to swell up like a balloon. The star’s diameter might increase hundreds of times during this phase. Our Red Giant star will also become very bright.

So Better wear your Sun glasses!!!