We Are All Star Stuff:

Discussion in 'Astronomy, Exobiology, & Cosmology' started by paddoboy, Jan 6, 2017.

  1. paddoboy Valued Senior Member

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    The elements of life mapped across the Milky Way by SDSS/APOGEE
    January 6, 2017

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    The six most common elements of life on Earth (including more than 97% of the mass of a human body) are carbon, hydrogen, nitrogen, oxygen, sulphur and phosphorus. The colors in the spectra show dips, the size of which reveal the amount of these elements in the atmosphere of a star. The human body on the left uses the same color coding to evoke the important role these elements play in different parts of our bodies, from oxygen in our lungs to phosphorous in our bones (although in reality all elements are found all across the body). In the background is an artist’s impression of the Galaxy, with cyan dots to show the APOGEE measurements of the oxygen abundance in different stars; brighter dots indicate higher oxygen abundance. Credit: Dana Berry/SkyWorks Digital Inc.; SDSS collaboration
    To say "we are stardust" may be a cliche, but it's an undeniable fact that most of the essential elements of life are made in stars.


    "For the first time, we can now study the distribution of elements across our Galaxy," says Sten Hasselquist of New Mexico State University. "The elements we measure include the atoms that make up 97% of the mass of the human body."

    The new results come from a catalog of more than 150,000 stars; for each star, it includes the amount of each of almost two dozen chemical elements. The new catalog includes all of the so-called "CHNOPS elements" – carbon, hydrogen, nitrogen, oxygen, phosphorous, and sulfur – known to be the building blocks of all life on Earth. This is the first time that measurements of all of the CHNOPS elements have been made for such a large number of stars.




    Read more at: http://phys.org/news/2017-01-elements-life-milky-sdssapogee.html#jCp
     
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  3. paddoboy Valued Senior Member

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    http://www.sdss.org/

    The Sloan Digital Sky Survey has created the most detailed three-dimensional maps of the Universe ever made, with deep multi-color images of one third of the sky, and spectra for more than three million astronomical objects. Learn and explore all phases and surveys—past, present, and future—of the SDSS.
     
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  5. Xelasnave.1947 Valued Senior Member

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    Thanks for this post and all the posts you make that I don't specifically thank you for Paddoboy.
    It seems like we have nearly covered everything with numbers like three million objects covered but its such a small part of the Universe.
    I was just reminded that even if it were three billion is is still such a small selection.
    I conclude the universe is big.
    Alex
     
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  7. paddoboy Valued Senior Member

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    Near infinite in fact, if not infinite

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    !
     
  8. Xelasnave.1947 Valued Senior Member

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    No its even bigger than that.

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    Alex
     
  9. Bowser Life is Fatal. Valued Senior Member

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    I followed your link, Paddoboy. It didn't give me anything to chomp on visually. Even after following several sub-links, I still didn't get any visual gratification. Looks more like a site that my wife's nephew might appreciate, the doctorate in astrophysics. If there's something in there that can wow the average Joe, please offer a link.
     
  10. paddoboy Valued Senior Member

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    The link simply confirms/restates what we already know.
     
  11. Bowser Life is Fatal. Valued Senior Member

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    I was hoping for something more like the below video...

     
  12. paddoboy Valued Senior Member

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    Here's another........................

    http://htwins.net/scale2/
     
  13. Bowser Life is Fatal. Valued Senior Member

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    That was cool! Thank you. I bookmarked it so I could show it to my daughter tomorrow.
     
  14. danshawen Valued Senior Member

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    "Vast."

    I think the series SG-1 has a similar moment in an episode about a linear network of stargate bucket brigades between the Milky Way and Pegasus galaxies. The disgust of the audience was palpable, like being told they are living in an actual universe. Thanks again for saving the day, Captain O.

    Knowing the compositions of 150,000 observable stars is of limited utility. All of the abundance of all of those elements contained by the Earth and dropped into a single small star would not register a hiccup on a spectrograph. "Trace amounts of star stuff" would be a more accurate characterization. Stars too are vast, compared to one minuscule planet circling a smallish one.
     
  15. exchemist Valued Senior Member

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    I had always thought ALL the elements, at least up to iron, were made in the stars. Are there some that aren't, and if so which ones?
     
  16. Seattle Valued Senior Member

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    Certainly hydrogen and helium.
     
  17. origin Trump is the best argument against a democracy. Valued Senior Member

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    And lesser amounts of Lithium and Beryllium.
     
  18. exchemist Valued Senior Member

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    Ah yes, these condensed out directly, after the Big Bang, didn't they? I was forgetting. What about heavier elements than these?
     
  19. paddoboy Valued Senior Member

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    Elements heavier then Iron/Nickel.....
    In catastrophic Supernova explosions.
     
    Last edited: Jan 7, 2017
  20. paddoboy Valued Senior Member

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  21. paddoboy Valued Senior Member

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    phttp://www.astro.ucla.edu/~wright/BBNS.html

    Gamow, Alpher and Herman proposed the hot Big Bang as a means to produce all of the elements. However, the lack of stable nuclei with atomic weights of 5 or 8 limited the Big Bang to producing hydrogen and helium. Burbidge, Burbidge, Fowler and Hoyle worked out the nucleosynthesis processes that go on in stars, where the much greater density and longer time scales allow the triple-alpha process (He+He+He -> C) to proceed and make the elements heavier than helium. But BBFH could not produce enough helium. Now we know that both processes occur: most helium is produced in the Big Bang but carbon and everything heavier is produced in stars. Most lithium and beryllium is produced by cosmic ray collisions breaking up some of the carbon produced in stars.

    The following stages occur during the first few minutes of the Universe:

    Less than 1 second after the Big Bang, the reactions shown at right maintain the neutron proton ratio in thermal equilibrium. About 1 second after the Big Bang, the temperature is slightly less than the neutron-proton mass difference, these weak reactions become slower than the expansion rate of the Universe, and the neutron proton ratiofreezes out at about 1:6.

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    After 1 second, the only reaction that appreciably changes the number of neutrons is neutron decay, shown at right. The half-life of the neutron is 615 seconds. Without further reactions to preserve neutrons within stable nuclei, the Universe would be pure hydrogen.

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    The reaction that preserves the neutrons is deuteron formation. The deuteron is the nucleus of deuterium, which is the heavy form of hydrogen (H2). This reaction is exothermic with an energy difference of 2.2 MeV, but since photons are a billion times more numerous than protons, the reaction does not proceed until the temperature of the Universe falls to 1 billion K or kT = 0.1 MeV, about 100 seconds after the Big Bang. At this time, the neutron proton ratio is about 1:7.

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    Once deuteron formation has occurred, further reactions proceed to make helium nuclei. Both light helium (He3) and normal helium (He4) are made, along with the radioactive form of hydrogen (H3). These reactions can be photoreactions as shown here. Because the helium nucleus is 28 MeV more bound than the deuterons, and the temperature has already fallen so far that kT = 0.1 MeV, these reactions only go one way.

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    The reactions at right also produce helium and usually go faster since they do not involve the relatively slow process of photon emission.

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    The net effect is shown at right. Eventually the temperature gets so low that the electrostatic repulsion of the deuterons causes the reaction to stop. The deuteron proton ratio when the reactions stop is quite small, and essentially inversely proportional to the total density in protons and neutrons. Almost all the neutrons in the Universe end up in normal helium nuclei. For a neutron proton ratio of 1:7 at the time of deuteron formation, 25% of the mass ends up in helium.

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    The mass fraction in various isotopes vs time is shown at right. Deuterium peaks around 100 seconds after the Big Bang, and is then rapidly swept up into helium nuclei. A very few helium nuclei combine into heavier nuclei giving a small abundance of Li7coming from the Big Bang. This graph is a corrected version of one from this LBL page. Note that H3decays into He3 with a 12 year half-life so no H3survives to the present, and Be7 decays into Li7 with a 53 day half-life and also does not survive.

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    The graph above shows the time evolution of the abundances of the light elements for a slightly higher baryon density. This figure is based on data from Burles, Nollett & Turner (1999). The asymptotic D/H ratio [by number] for this calculation is 1.78*10-5 which corresponds to OmegaBh2 = 0.029. The best current estimate is OmegaBh2 = 0.0214 +/- 0.002 from the D/H ratio measured in quasar absorption line systems, and OmegaBh2 = 0.0224 +/- 0.001 from the amplitudes of the acoustic peaks in the angular power spectrum of the CMB anisotropy.

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    The deuterium, He3, He4 and Li7 abundances depend on the single parameter of the current density of ordinary matter made out of protons and neutrons: baryonic matter. The graph above shows the predicted abundance vs. baryon density for these light isotopes as curves, the observed abundances as horizontal stripes, and the derived baryon density as the vertical stripe. A single value of the baryon density fits 4 abundances simultaneously. The fit is good but not perfect. There has been a dispute about the actual primordial helium abundance in the Universe: either 23.4 or 24.4 percent by mass, with both broups claiming 0.2 percent accuracy so this is 5 sigma discrepancy between the different observational camps. And a new measurement of the free neutron lifetime is 6 sigma smaller that the previous world average, giving a new prediction of the helium abundance of 24.6 percent. The observed lithium abundance in stars is less than the predicted lithium abundance, by a factor of about 2. But stars destroy lithium so it is hard to assess the significance of this difference.

    Other Big Bang Nucleosynthesis pages: LBL, Martin White.
     
  22. origin Trump is the best argument against a democracy. Valued Senior Member

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    Like you said elements up to iron in stars and the heavier elements are from novas and super novas.
     
  23. paddoboy Valued Senior Member

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    http://curious.astro.cornell.edu/ab...-are-light-and-heavy-elements-formed-advanced


    How are light and heavy elements formed? (Advanced)
    For an independent study course at my high school, I am researching the formation of the elements, both light and heavy. I have some basic understanding of how this is done, and I have also found some technical information that at this time I don't understand. Can you point me to some good articles on the topic, or perhaps cover some more advanced materials yourself?

    The lightest elements (hydrogen, helium, deuterium, lithium) were produced in the Big Bang nucleosynthesis. According to the Big Bang theory, the temperatures in the early universe were so high that fusion reactions could take place. This resulted in the formation of light elements: hydrogen, deuterium, helium (two isotopes), lithium and trace amounts of beryllium.

    Nuclear fusion in stars converts hydrogen into helium in all stars. In stars less massive than the Sun, this is the only reaction that takes place. In stars more massive than the Sun (but less massive than about 8 solar masses), further reactions that convert helium to carbon and oxygen take place in succesive stages of stellar evolution. In the very massive stars, the reaction chain continues to produce elements like silicon upto iron.

    Elements higher than iron cannot be formed through fusion as one has to supply energy for the reaction to take place. However, we do see elements higher than iron around us. So how did these elements form? The answer is supernovae. In a supernova explosion, neutron capture reactions take place (this is not fusion), leading to the formation of heavy elements. This is the reason why it is said that most of the stuff that we see around us come from stars and supernovae (the heavy elements part). If you go into technical details, then there are two processes of neutron capture called rapid process (r-process) and the slow process (s-process), and these lead to formation of different elements.

    For more details, refer the following websites:

    1. Big Bang nucleosynthesis

    2. Fusion in stars like the Sun

    3. s-process and r-process
     

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