What are the elements of earth?

What ratios of heavy elements are created by star-death, and can we extrapolate anything about the age/history of the universe based on the quantities/ratios present on Earth?

• In my lay-astrophysics education, I was taught that all elements heavier than Helium are the product of star-based fusion, and most of the elements heavier than Carbon are the product of late phases of star life, and their deaths.  There is an estimated ratio of heavy elements in our solar system (including the sun) that could be worked out, from the studies of composition, spectronomy, probe samples, etc.  We are also learning more about the statistical likelihood of exoplanets in other star system, based on an ever widening sample from indirect observation. How many generations of star birth and death would be necessary to account for this rough ratio of heavy elements? Given our understanding of star life spans (in the billions of years) and our current understanding of the age of the universe (less than twenty billion years), has there been enough time for stars to live and die, and make the ratios of heavy elements that we can currently observe?

• Answer:

  Short answer: yes Long answer: Nucleosynthesis is an extremely fascinating topic, and we've been able to work out the major processes.  The way that a nucleosynthesis calculation works is that you have this huge reaction matrix with the isotopes and nuclear reaction rates.  Then you set then under some conditions, and you can get a huge amount of detailed information. The two main processes to create heavily elements are the r-process which probably happens in supernova, and the s-process which we are pretty sure happens in red giants.  The number of generations seems right.  One thing about heavy elements is that they are produced in massive stars with short lifespans.  A 20 solar mass star will live for tens of millions of years rather than billions so that there have been a lot of generations of stars those stars that have lived.