Is Earth a failed star?

[Dubbelosix]

You asked what is non-mainstream. It might simply be that you are misinformed or are using terminology incorrectly.

No offense, but people need to start reading more carefully. I was sparing the persons feelings by trying to get on even ground, I even said in the following post that the terminology he was using was mumbo jumbo in the contexts he had given.

[Dubbelosix]

I am well aware of what is mainstream and what isn't.

[Swift]

Ok, let's stop the side conversation. Thanks,

[Ken G]

The issue seems to be the difference between a "failed" star and a "dying" star, as opposed to not using "star" language at all. If one wishes, one way to frame this issue is to say that any spread out high-mass ball of material is destined, as it loses heat and contracts, to end up as either a "failed star" (if it reaches its quantum mechanical ground state before ever undergoing significant fusion) or a "dead star" (if it does reach fusion, but then runs out of fuel). If one is to use that lens, one says every astrophysical object is currently either a star, a failed star, or a dying/dead star. Someone else might then bemoan the overuse of anthropomorphisms and analogies in place of precise language, but to each his/her own.

[George]

Wouldn’t it be handy to have a snazzy word that simply means non-star? Then we would have two separate categories of objects: Star types from O1 down; Non-star types from BD to perhaps meteoroids.

This would let failure to not be an option.

[DaCaptain]

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.

I had been thinking about this for a while and it seems that fusion is the more likely of the two to have happened. In order for a earth sized clump of uranium or plutonium to form and then spontaneously start a fission reaction seems out of the ordinary. Look at all the stars that are out there. Are any fission??? Why would fusion only be confined to star formation? Aren't the earth, the sun, and all the planets of our solar system approximately the same age and formed from the same soup.

[Hornblower]

I had been thinking about this for a while and it seems that fusion is the more likely of the two to have happened. In order for a earth sized clump of uranium or plutonium to form and then spontaneously start a fission reaction seems out of the ordinary. Look at all the stars that are out there. Are any fission??? Why would fusion only be confined to star formation? Aren't the earth, the sun, and all the planets of our solar system approximately the same age and formed from the same soup.

As has been said before, the Earth is not hot enough inside to induce a significant amount of exothermic fusion of light elements, and never has been. In ordinary stars there certainly is radioactive decay of uranium and thorium taking place, but these elements are only on the order of one part in a billion of their total mass, so the contribution to the star's luminosity is negligible. The ample amount of hydrogen fusion is what keeps them hot and stable for a long time. For Earth, where the fusion, if any, is negligible, the decay of uranium and thorium is a significant source of internal heat.

[DaCaptain]

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).

This post has been bugging me for a while. If all stars are fusion, how is it that earth starts a fission reaction rather than fusion? Isn't fusion more prolific through out the cosmos?
Which is easier to create?

[George]

This post has been bugging me for a while. If all stars are fusion, how is it that earth starts a fission reaction rather than fusion? Isn't fusion more prolific through out the cosmos?
Which is easier to create?

It is easy to cause fission, but fusion requires extreme conditions to take place. Uranium can split apart naturally, or if hit by a tiny neutrino or larger particle. For a single atom, this is barely noticeable. A controlled fission reaction takes more effort but nothing compared to fusion.

Stars that form from clouds will include whatever tiny amount of fissionable atoms were in the cloud. Planets have a higher concentration of these only because the lighter gasses can't be held by the planet's much weaker gravity. But the energy generated in a star by decaying atoms is peanuts compared to the energy generated by its collapse from a gigantic cloud fragment into a compressed "small" ball. Only with enough mass will the core temperatures rise high enough for hydrogen to combine in one or more ways to make helium. With enough mass, due to fusion, a star is born.

[Ken G]

This post has been bugging me for a while. If all stars are fusion, how is it that earth starts a fission reaction rather than fusion? Isn't fusion more prolific through out the cosmos?
Which is easier to create?

Fusion only releases energy when the nuclei are smaller than iron, and fission only releases energy when the nuclei are larger than iron. So which you get is entirely a matter of composition-- stars are made of small nuclei, rocky planets, large ones. And as pointed out, fusion requires high temperature because nuclei repel, fission does not.

[grapes]

Fusion only releases energy when the nuclei are smaller than iron, and fission only releases energy when the nuclei are larger than iron. So which you get is entirely a matter of composition-- stars are made of small nuclei, rocky planets, large ones. And as pointed out, fusion requires high temperature because nuclei repel, fission does not.

Or, typically, "fission bombs" are triggered by "fusion bombs." The easiest way to set up the extreme conditions necessary.

[Ken G]

I see what you mean, but I think you reversed it!

[grapes]

I see what you mean, but I think you reversed it!

D'oh! yes