Life+Cycle+of+a+Star



5.In order to prevent stars collapsing under their own gravity, some outward pressure must exist. this is supplied by the energy released by nuclear reactions in the core of the star. more massive stars need to burn their nuclear fuel at a much greater rate than smaller stars in order to produce enough energy to balance their much greater gravity. the difference in required reaction rates is actually greater than the difference in mass, consequently the more massive a star is, the faster it expends its fuel.

6.A medium-size star will live in the hydrogen phase, called the main sequence phase, for about 50 million years.

7.How long it takes for a star to die depends upon its initial mass. A lower-mass star like the sun can survive for billions of years, but after the hydrogen and helium fuel is gone it cannot get hot enough to fuse carbon.