As the temperature continues to drop, protons and neutrons can undergo fusion to form heavier atomic nuclei. Its harder and harder to make nuclei with higher masses.So the most common substance in the Universe is hydrogen (one proton), followed by helium, lithium, beryllium and boron (the first elements on the periodic table).Isotopes are formed, such as deuterium and tritium, but these elements are unstable and decay into free protons and neutrons. A key point is that the ratio of hydrogen to helium is extremely sensitive to the density of matter in the Universe (the parameter that determines if the Universe is open, flat or closed).Tags: Critical Thinking VideosArt Convergences Essay LiteratureTitle Of Term PaperPersuasive Essay Examples 5th GradeHow To Write A Research Paper On A BookGreat Essay 4 BookEssays On Performance Appraisals And FairnessCritical Thinking PuzzlesOnline Directory Business PlanEssay On Time Management In Life
Four protons are added, one by one, to a carbon nucleus to form a succession of excited (unstable) nuclei of carbon, nitrogen, and oxygen.
phase supplies energy to stars on the main sequence of the Hertzsprung-Russell diagram .
There are two chains of reactions by which the conversion of hydrogen to helium is effected: the proton-proton cycle and the carbon-nitrogen-oxygen cycle (sometimes referred to simply as the carbon cycle). The proton-proton cycle operates in less massive and luminous stars like the sun, while the carbon-nitrogen-oxygen cycle (which speeds up dramatically at higher temperatures) dominates in more massive and luminous stars.
Thus, elements heavier than iron cannot be fuel sources in stars.
And, likewise, elements heavier than iron are not produced in stars, so what is their origin? The construction of elements heavier than Fe (iron) involves nucleosynthesis by neutron capture.