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Thread: Oldest known, iron deficient star discovered

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    Default Oldest known, iron deficient star discovered



    Researchers discovered a roughly 13.7B years old star that was formed shortly after the big-bang. A very interesting thing about this star is that it has barely any iron, but comparatively high amount of carbon and magnesium, which can offer some important clues on the evolution of primordial stars.

    "This incredibly anaemic star, which likely formed just a few hundred million years after the Big Bang, has iron levels 1.5 million times lower than that of the Sun"

    Paper: https://arxiv.org/pdf/1904.07471.pdf
    Last edited by drolem; 08-07-2019 at 10:52 AM.

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    Default Re: Oldest known, iron deficient star discovered

    This is a discussion that appeared elsewhere:

    https://theskysearchers.com/viewtopic.php?f=74&t=2111
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    Default Re: Oldest known, iron deficient star discovered

    While articles written for general 'consumption' are good since research papers may have too much technical details that can make them hard to understand, sometimes they may leave important things out, or make inadvertent errors like below in this not very well explained paragraph that is incorrect in a number of ways.

    The very first stars in the Universe are thought to have consisted of only hydrogen and helium, along with traces of lithium. These elements were created in the immediate aftermath of the Big Bang, while all heavier elements have emerged from the heat and pressure of cataclysmic supernovaeā€”titanic explosions of stars. Stars like the Sun that are rich in heavy element therefore contain material from many generations of stars exploding as supernovae.
    specifically: "all heavier elements have emerged from the heat and pressure of cataclysmic supernovae"

    1. Up to Fe, heavier elements can be made by fusion
    2. There are a number of different types of supernovaes, and not all will make some of the heavier elements
    3. Stars can shed material in other ways (i.e. planetary nebula)
    4. The s-process (red giants!) can create elements beyond Fe, but it's kinda slow and it can go only up to lantanides, not actinides,

    Merging neutron stars in particular can utilize the r-process which can then create the create many heavier elements, up to and including actinides, and maybe even beyond that, although the half life of most anything beyond U238 in most cases is short enough that they won't stay around very long. In particular, Np and Pu has some isotopes whose life is measured in thousands of years, but that's still a very short time in a cosmic scale.

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    Default Re: Oldest known, iron deficient star discovered

    Quote Originally Posted by drolem View Post
    While articles written for general 'consumption' are good since research papers may have too much technical details that can make them hard to understand, sometimes they may leave important things out, or make inadvertent errors like below in this not very well explained paragraph that is incorrect in a number of ways.

    "The very first stars in the Universe are thought to have consisted of only hydrogen and helium, along with traces of lithium. These elements were created in the immediate aftermath of the Big Bang, while all heavier elements have emerged from the heat and pressure of cataclysmic supernovaeāā‚¬ā€titanic explosions of stars. Stars like the Sun that are rich in heavy element therefore contain material from many generations of stars exploding as supernovae."

    specifically: "all heavier elements have emerged from the heat and pressure of cataclysmic supernovae"
    No, you are more mistaken than the article, sorry. See below.

    The first stars in the universe were made of H and He with traces of Li. Their mass distribution was very different from the mass distribution at the present time because the first generation of stars had no heavier elements to provide opacity. While the first generation was able to synthesize elements up to C, N, O in stars they were unable (low opacity again) to disperse that enrichment to other stars because the only means available to them was a supernova.

    For instance lower mass stars can enrich the galactic abundance of C, N, and O by passing through a planetary nebula stage, shedding a lot of the envelope. This mechanism wasn't available to the 1st generation of stars which were too massive.

    So the 1st generation of stars could ONLY enrich the interstellar medium via supernovae.

    You are making an out of context criticism of the article.

    1. Up to Fe, heavier elements can be made by fusion
    But beyond C, N, O these elements ONLY get dispersed in supernovae.

    2. There are a number of different types of supernovaes, and not all will make some of the heavier elements
    True. But the first generation of stars had a very limited repertoire of supernova types from which to choose,

    3. Stars can shed material in other ways (i.e. planetary nebula)
    But again that isn't happening in the first generation of stars.

    4. The s-process (red giants!) can create elements beyond Fe, but it's kinda slow and it can go only up to lantanides, not actinides,
    With the spelling correction "lanthanides" true.

    Merging neutron stars in particular can utilize the r-process which can then create the create many heavier elements, up to and including actinides, and maybe even beyond that, although the half life of most anything beyond U238 in most cases is short enough that they won't stay around very long. In particular, Np and Pu has some isotopes whose life is measured in thousands of years, but that's still a very short time in a cosmic scale.
    Where you have gone wrong is misreading the context of the article. The article is about a star whose pattern of enrichment indicates that it is from the 2nd generation of stars, enriched by one prior supernova. So your criticism is flawed.
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    Default Re: Oldest known, iron deficient star discovered

    PS The point of this research is that the abundances of this star are compatible with enrichment from the primordial abundance by one supernova event only, making this only a second generation star. Other enrichment mechanisms (planetary nebulae, etc.) are irrelevant because they only start working after many generations of star formation. In addition the pattern of abundances rule out alternatives.
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