A typical star begins as a thin cloud of hydrogen gas that, under the force of gravity, collects into a huge, dense sphere. When the new star reaches a certain size, a process called nuclear fusion ignites, generating the star's vast energy.
Elements are created inside active stars by nuclear reactions called stellar nucleosynthesis . The mass and type of the star, temperatures within it, and where it is in its life cycle (which fuels ...
THE ORIGIN OF THE ELEMENTS AND THE LIFE OF A STAR. The chemical elements have not always existed. Their nuclei can not have a huge age, for if they did, the radioactive nuclei would have already vanished. They could be twice as old as the Earth, for instance, but not ten times as old.
The Chemical Composition of Stars and the Universe ... Cecilia Payne studied the spectra of stars, and devised a way to figure out the temperature and true chemical composition of stars. She concluded that the atmospheres of stars were ... helium fuses into heavy elements (in high-mass stars)
Stars have been forming since the Universe began. In fact, astronomers calculate that 5 new stars form in the Milky Way every year. Some have more of the heavier elements left over from previous ...
Stars are made mostly of hydrogen and helium in the plasma state.Traces of heavier elements can also be found. When stars form, they are composed of approximately 70% hydrogenand 28% helium, the ...
Astronomers label all elements heavier than helium "metals", and call the chemical concentration of these elements in a star, its metallicity. A star's metallicity can influence the time the star takes to burn its fuel, and controls the formation of its magnetic fields, which affects the strength of its stellar wind.
Stellar nucleosynthesis is the theory explaining the creation (nucleosynthesis) of chemical elements by nuclear fusion reactions between atoms within stars. Stellar nucleosynthesis has occurred continuously since the original creation of hydrogen, helium and lithium during the Big Bang. It is a highly predictive theory that today yields ...
Further fusion processes can create heavier elements such as silicon, magnesium and sodium. However, the abundance of these elements in most stars is very low and accounts for less than 1 percent of the mass. Fusion within stars can only account for the creation of elements up to the mass of iron.
How do stars form and evolve? Stars are the most widely recognized astronomical objects, and represent the most fundamental building blocks of galaxies. The age, distribution, and composition of the stars in a galaxy trace the history, dynamics, and evolution of that galaxy. Moreover, stars are responsible for the manufacture and distribution of heavy elements such as carbon, nitrogen, and ...