Space Rumors

A star once it forms and begins to shine is a stable body that remains practically unchanged for many years. In the nucleus of a star, near its center, hydrogen is being converted into helium. The energy produced makes the interior of the star extraordinarily hot. This energy escapes from the surface of the star in the form of light and heat. The gas formed by the star tends to expand, and is capable of supporting the weight of the star itself, stopping its contraction. This situation lasts as long as there is enough hydrogen in the center of the star. Stars spend about 90% of their lifetime fusing hydrogen to produce helium in high-temperature and high-pressure reactions near the core. Such stars are said to be on the main sequence and are called dwarf stars, the Sun, for example, is estimated to have increased in luminosity by about 40% since it reached the main sequence 4.6 billion years ago. Every star generates a stellar wind of particles that causes a continual outflow of gas into space. For most stars, the amount of mass lost is negligible.

The Sun loses 10−14 solar masses every year, or about 0.01% of its total mass over its entire lifespan. However very massive stars can lose 10−7 to 10−5 solar masses each year, significantly affecting their evolution. Stars that begin with more than 50 solar masses can lose over half their total mass while they remain on the main sequence. The time for the main sequence depends on the amount of the fuel its having to fuse and the rate at which it fuses the fuel i.e. its initial mass and its luminosity. Large stars consume their fuel very rapidly and were short lived, but the small stars (red dwarfs) consume their mass very slowly and live for billions of years and at the final stage they become dimmer and dimmer. Since the age of the universe is 13.7 billion years, no red dwarfs have reached to that position.