The Formation of the Elements, and of us
At the bottom of this entry, I give the Weekly Pondering 10 assignment, for those of you in ASTR 1/2. Any text that you need to read is on Blackboard or linked to here.
10: The Formation of the Elements, and of us
One of the most obviously integral topics in astronomy is that of the lives and deaths of stars. Perhaps just as important, but maybe less obvious, is how cosmic events are connected to phenomena on Earth. It was Isaac Newton who first proposed a model of gravitation which connected the movement of the “heavenly” bodies to the movement of objects on Earth. In Astronomy 1 we have learned about the spectra of stars, and we have learned that we can identify spectral lines that we find in stars with spectral lines that we observe for atoms in experiments on Earth. This is the field of spectroscopy, and it gives us confidence that stars are not only made of atoms, but particular and identifiable atoms. (Although we don’t discuss this much, spectroscopy is applied to temperate and cold bodies in addition to stars, inside and outside of the Solar System.)
Thus far, however, we have not discussed where the elements come from. In this Weekly Pondering, we will do just that. Below, we link to the first 7 pages of chapter IX from one of Carl Sagan’s most well-known works, Cosmos. Please read this chapter, and watch the video that is embedded above. In a sentence or two, describe where the elements come from. Below, we reproduce a table which lists estimates for the abundances for common elements heavier than Hydrogen and Helium, which are the two most common elements in the universe, in a portion of the Milky Way galaxy--and this closely approximates the abundances throughout the galaxy. (These are abundances by number of elements, not by mass.) What are the two next most common elements in our galaxy, according to the table? Do a little research on the four most common elements in the human body. Is there overlap? Briefly describe your answers to these questions, in a paragraph or so. Is there some interesting significance here?
Please click on the top link to the left to see the proportion of the elements in the galaxy, and click on the bottom link to the left to read chapter IX from Cosmos. If you have trouble logging, please see the note below regarding the login procedure to submit. (The credentials needed for all of these links are the same.)
Wilson, T. L., and R. T. Rood. "Abundances in the interstellar medium." Annual Review of Astronomy and Astrophysics 32.1 (1994): 191-226.
Submit WP 10 here:
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