Brief reminder of Part 1 (without mistake ) :
Stars are born at the heart of vast clouds of gas and dust, made up of tiny particles that clump together. Gravity increases their volume by attracting more matter.
After thousands of years, pockets of dense matter in the nebula colapse under their own weight due to gravity. One of these compressed masses of gaz, called a protostar, is the fledgling star. The slumping of the cloud creates a disc that rotates around the protostar. During this stage, matter is transferred from the cloud to the disc and then to the star. Millions of years later, as the temperature of the star ' s core reache 15 million degres Celsius, fusion begins, setting the core ablaze and triggering thermonuclear reactions, giving birth to a star.
Nuclear fusion produce an enormous amount of energy that exerts pressure outward and counterbalances the gravity that is trying to make the star collapse. This delicate balance generated by gravity and pressure will last the entire life of the star.
Depending on the mass corresponding to the matter that the star posseses, it will die either quietly or spectacularly by implode, accompanied by a brief but fantastic increase in luminosity.
Our Sun is of average size compared with other stars in the univers. However, it is the largest star in our galaxy, estimate to be 110 times larger than the Earth. |
