It is now known that the elements observed in the Universe were created in either of two ways. Light elements namely deuterium, helium, and lithium were produced in the first few minutes of the Big Bang, while elements heavier than helium are thought to have their origins in the interiors of stars which formed much later in the history of the Universe. Both theory and observation lead astronomers to believe this to be the case.
So where were they formed?
B - Proto-stars and Star formation Stars form in nebulae and clouds. The major part of interstellar gas exists in the form of neutral material, basically atomic and molecular hydrogen.
Spectroscopic observations at centimeter and millimeter wavelengths have allowed astronomers to determine that the major part of interstellar material is concentrated in giant molecular clouds with a mass ranging between ten thousand and one million times the mass of the Sun. This fact makes them the most massive objects in the galaxy.
Observations of interstellar molecules have revealed that the major part of the gas in these clouds is extremely cold, with temperatures ranging between and degrees Celsius and with average densities of a few hundreds of molecules every cubic centimeter.
One of the most important aspects in the study of molecular clouds is the fact that it is in the most dense condensations of these clouds where new stars are born. In the case of the Milky Way this takes place at a rate of suns per year, approximately.
Due to the high visual extinction associated with these condensations, the physical processes involved in the star formation take place in extremely dark regions and, therefore, are only accessible by means of observations in the far infrared and at radio wavelengths -- from submillimeter to centimeter wavelengths This image, taken by the Hubble Space Telescopeshows gaseous pillars in a star-formation region of the Eagle Nebula also known as M16, or Messier For further details, read the complete caption.
Visit the Hubble server for more images of this phenomenon. This is a schematic view of the process of star formation, obtained from Prof. Check out her talk on Star formation. Inside these galaxies, other clumps began to collapse under gravity into smaller bodies.
These new stars continued to collapse and heat up. After perhaps 10 or million years of this steady collapse, the internal temperature of the new star reached a value of about 10 million degrees proton energies of about 1 keVand thermonuclear reactions between the protons in the gas began.
Nuclear fusion reactions are now accepted to be the source of energy in the starts. Until recently this fact was based on circumstantial evidence only. This is because the light we observe from stars is emitted in their surface, and we cannot look inside them to determine what is going on.
One of the early evidences that nuclear reactions occur in stars was the observation of spectral lines of an element called technetium on the surfaces of certain old stars.
Technetium has no stable isotopes, i.May 01, · Stellar nucleosynthesis is the only theory we currently have that involves laboratory tested physics that could explain that. Direct evidence involves detection of solar neutrinos.
In fact, the established field of neutrino oscillations was born by looking at the discrepancy between predictions and observations surrounding solar . EVIDENCE FOR A SINGLE STELLAR ENVIRONMENT OF R-PROCESS NUCLEOSYNTHESIS FROM LIVE Cm IN THE EARLY SOLAR SYSTEM.
F. L. H Tissot1,2, N. Dauphas1, L.
Grossman3, 1Origins Lab, Department of the Geophysical Sciences and Enrico Fermi Institute, The University of Chicago, IL. Stellar & Supernovae Nucleosynthesis And Cosmic Chemical Evolution Jim Truran Argonne National Laboratory “The First Stars and Evolution of the Universe” Institute for Nuclear Theory, Seattle no compelling evidence for a distinct earlier stellar .
In physical cosmology, Big Bang nucleosynthesis by stellar nucleosynthesis in evolving and exploding stars. Characteristics That the observed abundances in the universe are generally consistent with these abundance numbers is considered strong evidence for the Big Bang theory.
Stellar Nucleosynthesis – ThoughtCo Stellar nucleosynthesis creates heavier elements from hydrogen and the big bang theory but believed instead that hydrogen was continually nbsp; Stellar nucleosynthesis – ScienceDaily is the collective term for the nuclear reactions taking place in stars to build the nuclei of the heavier elements.
May 01, · Stellar nucleosynthesis is the only theory we currently have that involves laboratory tested physics that could explain that.
Direct evidence involves detection of solar neutrinos. In fact, the established field of neutrino oscillations was born by looking at the discrepancy between predictions and observations surrounding solar neutrinos.