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Thread: Is Earth a failed star?

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    Is Earth a failed star?

    I've often wondered, is the earth really just a failed star?
    I know that I know nothing, so I question everything. - Socrates/Descartes

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    Quote Originally Posted by DaCaptain View Post
    I've often wondered, is the earth really just a failed star?
    No.

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    No, it's a successful planet.

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    I'd like to point out that the phrase "failed star" is not a technical term with a specific meaning. I recall Arthur C Clarke using it to describe Jupiter in one of his works of fiction, but even Jupiter is a stretch to call a failed star.
    I take the term, these days, to refer to some object that formed as one of several starless cores in a protostellar cloud, and one or more of the other cores became stars first, and blew away enough material around this core that never became even a red dwarf. (Exo)planets form after the core the orbit becomes a star using a different process. It is possible that some environments will result in sequences of events where some objects will be in a gray area between the two, but at the moment, there is no need for being able to precisely identify every case, so the terminology remains fuzzy.
    Forming opinions as we speak

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    Future star material.
    The moment an instant lasted forever, we were destined for the leading edge of eternity.

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    Quote Originally Posted by DaCaptain View Post
    I've often wondered, is the earth really just a failed star?
    My reasoning for this question is that the core doesn't seem to be cooling down. There's got to be a fusion reaction going on in the center that's been keeping it going for so long. It's not as hot as the sun so that's why I was thinking, failed star. Doesn't seem like geomagnetic forces alone could account for all the heat that's been generated during it's lifetime. Without a reaction I'd think that after a while everything would have become tidally locked and cooled down, like Mars, a long time ago.
    I know that I know nothing, so I question everything. - Socrates/Descartes

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    Quote Originally Posted by DaCaptain View Post
    My reasoning for this question is that the core doesn't seem to be cooling down. There's got to be a fusion reaction going on in the center that's been keeping it going for so long. It's not as hot as the sun so that's why I was thinking, failed star. Doesn't seem like geomagnetic forces alone could account for all the heat that's been generated during it's lifetime. Without a reaction I'd think that after a while everything would have become tidally locked and cooled down, like Mars, a long time ago.
    I think there have been suggestions that fusion takes place in the earth's core, but there is not a consensus that it does or doesn't.
    As above, so below

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    Quote Originally Posted by Jens View Post
    I think there have been suggestions that fusion takes place in the earth's core, but there is not a consensus that it does or doesn't.
    The only suggestions for any significant level of fusion in the core I've seen come from cold fusion advocates and are not backed by credible evidence.

    Quote Originally Posted by DaCaptain View Post
    My reasoning for this question is that the core doesn't seem to be cooling down. There's got to be a fusion reaction going on in the center that's been keeping it going for so long. It's not as hot as the sun so that's why I was thinking, failed star. Doesn't seem like geomagnetic forces alone could account for all the heat that's been generated during it's lifetime. Without a reaction I'd think that after a while everything would have become tidally locked and cooled down, like Mars, a long time ago.
    You might want to run some numbers (or read some papers on models which do) for that. Currently models suggest that the core is cooling, just slowly. The energy budget, once you include radioactive decay, latent heats of crystallisation and frictional heating, shows a small deficit from equilibrium conditions. The collision with the object that led to the Moon's formation helped stir things up by injecting a large pulse of heat. Mars is a poor comparison because it is much smaller and didn't have a Theia event. These factors lead to the lower core temperature estimate of 1500K for Mars (but it may be partly liquid). It also isn't tidally locked.

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    Quote Originally Posted by DaCaptain View Post
    My reasoning for this question is that the core doesn't seem to be cooling down. There's got to be a fusion reaction going on in the center that's been keeping it going for so long.
    If you replace "fusion" with "fission," then your thinking is correct. Note that fusion releases heat from building larger nuclei from smaller ones (like hydrogen into helium in stars), whereas fission releases heat by breaking up very large nuclei (like uranium and plutonium). There isn't hydrogen and helium in Earth's core, and the temperature is not high enough anyway, so it's not so much failing at fusion as it is succeeding at fission.

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    I recall the great Kelvin calculated that the Earth should have cooled down but he did not know about fission, so the fission contribution might be significant. But then were the solar balances and the current idea of the history well understood by Kelvin?
    sicut vis videre esto
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    Quote Originally Posted by profloater View Post
    I recall the great Kelvin calculated that the Earth should have cooled down but he did not know about fission, so the fission contribution might be significant.
    Yes, he used his knowledge of heat transfer and thermodynamics to calculate the time needed to cool the Earth from an assumed molten state, as was deemed likely upon formation. He had temperature gradient data taken in mines and calculated, initially IIRC, a 20 million year age. He later received deeper mine temp. data, I think, and came up with 100 million years. Darwin called him an "odious specter" since that was too young an age for his evolutionary theory.

    Along came Rutherford with his new knowledge of radioactive decay and in a dramatic meeting, which Kelvin attended, the somewhat apprehensive Rutherford pointed out Lord Kelvin's error, but he carefully crafted his words.


    But then were the solar balances and the current idea of the history well understood by Kelvin?
    Yes, no doubt, since even IR (from Herschel's discovery) was known in 1800, decades before Kelvin's work.

    It's worth mentioning, per what I've learned from Ken's posts in the past, that internal convection plays an important role as well.
    We know time flies, we just can't see its wings.

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    Quote Originally Posted by Shaula View Post
    You might want to run some numbers (or read some papers on models which do) for that. Currently models suggest that the core is cooling, just slowly. The energy budget, once you include radioactive decay, latent heats of crystallisation and frictional heating, shows a small deficit from equilibrium conditions. The collision with the object that led to the Moon's formation helped stir things up by injecting a large pulse of heat. Mars is a poor comparison because it is much smaller and didn't have a Theia event. These factors lead to the lower core temperature estimate of 1500K for Mars (but it may be partly liquid). It also isn't tidally locked.
    Last time I looked, it seemed the greatest effect on the model was that the radioactive decay was concentrated near the surface, biasing those heat loss calculations. Left over heat of formation was the largest part of the budget in the core.

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    Quote Originally Posted by Ken G View Post
    If you replace "fusion" with "fission," then your thinking is correct. ....
    That was kind of my thinking in the first place. It failed to get the materials it needed for fusion.
    I know that I know nothing, so I question everything. - Socrates/Descartes

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    Quote Originally Posted by George View Post
    Yes, he used his knowledge of heat transfer and thermodynamics to calculate the time needed to cool the Earth from an assumed molten state, as was deemed likely upon formation. He had temperature gradient data taken in mines and calculated, initially IIRC, a 20 million year age. He later received deeper mine temp. data, I think, and came up with 100 million years. Darwin called him an "odious specter" since that was too young an age for his evolutionary theory.

    Along came Rutherford with his new knowledge of radioactive decay and in a dramatic meeting, which Kelvin attended, the somewhat apprehensive Rutherford pointed out Lord Kelvin's error, but he carefully crafted his words.


    Yes, no doubt, since even IR (from Herschel's discovery) was known in 1800, decades before Kelvin's work.

    It's worth mentioning, per what I've learned from Ken's posts in the past, that internal convection plays an important role as well.
    thanks for that, fills in the details.
    sicut vis videre esto
    When we realize that patterns don't exist in the universe, they are a template that we hold to the universe to make sense of it, it all makes a lot more sense.
    Originally Posted by Ken G

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    Quote Originally Posted by DaCaptain View Post
    That was kind of my thinking in the first place. It failed to get the materials it needed for fusion.
    That's taking it a little too far--we're all failed stars then

    ETA: usually, "failed star" implies getting close to being, not just a complete miss.

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    Quote Originally Posted by grapes View Post
    Last time I looked, it seemed the greatest effect on the model was that the radioactive decay was concentrated near the surface, biasing those heat loss calculations. Left over heat of formation was the largest part of the budget in the core.
    Why would this be the case? Uranium is heavy. Or is it because the outer 2km comprises a volume for its shell > the core volume?
    We know time flies, we just can't see its wings.

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    Quote Originally Posted by profloater View Post
    thanks for that, fills in the details.
    Also quite interesting is that Kelvin's age for the Earth matched the independent calculation for the age of the Sun (gravity; virial theorem), adding to Darwin's frustration. Multiple lines of evidence are sometimes just coincidental, just not often.
    Last edited by George; 2018-May-24 at 04:48 PM.
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    Quote Originally Posted by George View Post
    Why would this be the case? Uranium is heavy. Or is it because the outer 2km comprises a volume for its shell > the core volume?
    I'm no expert, but this link ( https://earthscience.stackexchange.c...ore-is-uranium ) gives its reasoning for concluding:
    This means that relative to solar system abundances, all three of these elements should be strongly enhanced in the Earth's crust, slightly depleted in the Earth's mantle, and strongly depleted in the Earth's core.
    The three are potassium, uranium, and thorium

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    I guess its a good thing uranium isn't concentrated in the core or it might go critical. (Not intended completely seriously)

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    Quote Originally Posted by grapes View Post
    I'm no expert, but this link ( https://earthscience.stackexchange.c...ore-is-uranium ) gives its reasoning for concluding:
    That almost eschews obfuscation. I found other sources agreeing with the claim but with little explanation, though I'm not spending a lot of time on it. I think it may be that only potassium can combine with iron to allow it to sink into the core, and the other radioactive elements do combine with lighter elements, which may keep them from sinking as much, I suppose. More likely is that meteorite data ratios are used to determine these things and potassium comes up very high in meteorites compared to the surface, so core concentration is one explanation for it.

    This article addresses the above, and suggests to me that the other elements are higher in concentration for the surface than found in meteorites, so less in the core, no doubt is the logic. [This assumes Earth's formation region was similar to the asteroid belt's region for radioactive elements, which isn't illogical, I suppose.]
    Last edited by George; 2018-May-24 at 06:19 PM.
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    Uranium and thorium are highly reactive chemically, and the crust is vastly enriched in them compared with the universe as a whole.

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    Quote Originally Posted by DaCaptain View Post
    That was kind of my thinking in the first place. It failed to get the materials it needed for fusion.
    That would be part of the story, but not all of it, because you also need very high temperature. That's the sense to which Jupiter is a "failed star," because it has the hydrogen, but not high enough temperature. You could then say that the Earth is a doubly failed star, but it starts to get pretty far fetched when it's that far from being a star!

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    Quote Originally Posted by Ken G View Post
    That would be part of the story, but not all of it, because you also need very high temperature. That's the sense to which Jupiter is a "failed star," because it has the hydrogen, but not high enough temperature. You could then say that the Earth is a doubly failed star, but it starts to get pretty far fetched when it's that far from being a star!
    Hmm, when a star forms is it always a fusion reaction? Are there such things as fission stars?
    I know that I know nothing, so I question everything. - Socrates/Descartes

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    Quote Originally Posted by DaCaptain View Post
    Hmm, when a star forms is it always a fusion reaction? Are there such things as fission stars?
    It's always fusion, yes. Brown dwarfs are defined as not fusing normal hydrogen but fusing deuterium, and even those are not officially stars (though many regard them as a type of star).

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    Quote Originally Posted by Shaula View Post
    The only suggestions for any significant level of fusion in the core I've seen come from cold fusion advocates and are not backed by credible evidence.
    Yes, that sounds right I suppose. I was basing what I wrote on a paper (https://www.nature.com/articles/srep37740) that I thought was in Nature Communications, but now I see it's Scientific Reports, so not very significant.
    As above, so below

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    The way I understand it, Earth is the product of what happens to a failed star.... the star fails, loses enough energy to finally inflate, and hopefully go supernova. The Earth is what the failed star has regurgitated.

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    Also, as Grapes has mentioned, a ''failed star'' usually has a specific terminology any way.

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    Quote Originally Posted by Dubbelosix View Post
    The way I understand it, Earth is the product of what happens to a failed star.... the star fails, loses enough energy to finally inflate, and hopefully go supernova. The Earth is what the failed star has regurgitated.
    The way you (mis)understand it is not mainstream science. The Space/Astronomy Questions and Answers subforum is where folks get mainstreams answers to their questions. ATM responses are not allowed.
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    Quote Originally Posted by PetersCreek View Post
    The way you (mis)understand it is not mainstream science. The Space/Astronomy Questions and Answers subforum is where folks get mainstreams answers to their questions. ATM responses are not allowed.
    Ok... but where is my non-mainstream answer? We are leftovers of a star that went supernova a long time ago.

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    Quote Originally Posted by Dubbelosix View Post
    The way I understand it, Earth is the product of what happens to a failed star.... the star fails, loses enough energy to finally inflate, and hopefully go supernova. The Earth is what the failed star has regurgitated.
    You asked what is non-mainstream. It might simply be that you are misinformed or are using terminology incorrectly. A failed star does not go supernova, because a failed star is understood as "an object that came close to becoming a star but failed to get fusion going." Such an object will never go supernova. It is very large stars that become supernova at the end of their lives, so they are very successful stars. For example, the sun will not become a supernova because it is not massive enough. And I also wonder what you mean by "hopefully." It's a simple process, not something that one hopes for. In fact, if you are a civilization that is located near the star, then "hopefully" it will not go supernova...

    And it is true that some of the elements on the earth are from supernova or perhaps neutron star mergers (I guess), but not everything is. I think that the hydrogen and helium may be primordial, but I could be wrong about this.
    As above, so below

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