13 Dec 21
@Metal-Brain
It is not a solid core but that doesn't detract from the overall theme, they grow till gravity overcomes the pressures keeping fusion from happening so at some point it starts up the fusion process.
13 Dec 21
@sonhouse saidThe fusion of what elements?
@Metal-Brain
It is not a solid core but that doesn't detract from the overall theme, they grow till gravity overcomes the pressures keeping fusion from happening so at some point it starts up the fusion process.
Only big stars fuse heavier elements, not small stars. A small star fuses hydrogen into helium. The core of heavier elements in a star don't fuse together unless it is a big star and it exhausts the lighter elements.
What he is asserting doesn't make much sense. He needs to explain how heavy elements can fuse in a small star. I am assuming that is what he means by solid, but nothing is solid in the core of a huge planet. Too hot.
13 Dec 21
@metal-brain saidTrue -- the core wouldn't be a solid like a stone in your hand, but a hot, compressed sludge of matter resembling more a solid than gas.
"If it continues to grow, the solid core eventually ignites via fusion."
What is your source of information?
Stop calling it solid. You don't call the earth's core solid, do you? Liquid iron is not solid.
As for the proof that big masses ignite via fusion -- the stars you see at night. If they didn't ignite, stars wouldn't exist.
And if rocky or iron cores prevented fusion, then a planet would keep growing until it's thousands or millions of times bigger than Jupiter, something not yet seen, unless of course those those gigantic masses collapse into neutron stars without ever becoming stars, which also has not been seen.
13 Dec 21
@bunnyknight saidMy point is that if a metal core of mostly iron was large enough there would be less hydrogen and it would surround a big core. I doubt there would be enough pressure and heat from gravity to ignite a fusion reaction if the hydrogen is not in abundance. That would explain why it didn't turn into a star.
True -- the core wouldn't be a solid like a stone in your hand, but a hot, compressed sludge of matter resembling more a solid than gas.
As for the proof that big masses ignite via fusion -- the stars you see at night. If they didn't ignite, stars wouldn't exist.
And if rocky or iron cores prevented fusion, then a planet would keep growing until it's thousands or ...[text shortened]... gantic masses collapse into neutron stars without ever becoming stars, which also has not been seen.
How big is the core of Jupiter in relation to the surrounding gas? Did the Voyager 1 or 2 measure that?
13 Dec 21
@bunnyknight saidThanks for the education.
Absolutely. Eventually either pressure or gravity will cause something catastrophic to happen. I think the core would undergo fusion long before it collapses into neutron matter.
Scientists still don't know exactly how big a rocky planet can get. So far the biggest rocky planet they found is about 40 Earth masses.
I think of course the max planet size can be determined empirically by looking at thousands of planets to see what the largest ones are. But is there a theoretical max? If a 40 earth mass planet exists, then why not 41 (theoretically)? What conditions would support the existence of very large solid mass planets?
14 Dec 21
@metal-brain saidI sure would love to explore Jupiter's core if I could. I wonder if it even has a solid surface beneath all that gas, or perhaps liquid hydrogen. Some have even speculated that the core is diamond. Of course to get down there you'd need a hard pressure suit to avoid getting squished by the air pressure.
My point is that if a metal core of mostly iron was large enough there would be less hydrogen and it would surround a big core. I doubt there would be enough pressure and heat from gravity to ignite a fusion reaction if the hydrogen is not in abundance. That would explain why it didn't turn into a star.
How big is the core of Jupiter in relation to the surrounding gas? Did the Voyager 1 or 2 measure that?
As for fusion taking place, I wonder if an iron core could still exist unfused while hydrogen is fusing all around it. Another words, hydrogen would be fusing while iron plasma would remain intact.
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14 Dec 21
@wildgrass saidThere is a (multi-directional) spectrum, and it depends on the composition. For more (and more accurate!) information, try https://en.wikipedia.org/wiki/Brown_dwarf and take it from there.
Thanks for the education.
I think of course the max planet size can be determined empirically by looking at thousands of planets to see what the largest ones are. But is there a theoretical max? If a 40 earth mass planet exists, then why not 41 (theoretically)? What conditions would support the existence of very large solid mass planets?
14 Dec 21
@wildgrass saidI don't think anyone knows the exact maximum planet size or mass. The thing with massive planets is that their strong gravity attracts gas, and they eventually puff up like a giant fluffy pillow, so it's impossible to see how big the solid part actually is.
Thanks for the education.
I think of course the max planet size can be determined empirically by looking at thousands of planets to see what the largest ones are. But is there a theoretical max? If a 40 earth mass planet exists, then why not 41 (theoretically)? What conditions would support the existence of very large solid mass planets?
14 Dec 21
@bunnyknight saidYes, I was wondering the same thing. I assume all stars have a core of mostly iron and other heavy elements. That is where the gravity is. I have no idea how big the cores are in stars. Impossible to know with all that intense solar radiation.
I sure would love to explore Jupiter's core if I could. I wonder if it even has a solid surface beneath all that gas, or perhaps liquid hydrogen. Some have even speculated that the core is diamond. Of course to get down there you'd need a hard pressure suit to avoid getting squished by the air pressure.
As for fusion taking place, I wonder if an iron core could stil ...[text shortened]... using all around it. Another words, hydrogen would be fusing while iron plasma would remain intact.
I am guessing the size of the core would make a difference. A bigger core would have more surface area where the hydrogen meets it. I am guessing there would be less pressure than a small core with more pressure on less surface area.
"hydrogen would be fusing while iron plasma would remain intact"
I am sure that is the case in all stars in recent history. Heavier elements must be at the core of stars. That is where the most gravity is. The question is, does the size of the core make a difference between fusion or no fusion? I am not sure, but I think it does make that difference depending on how big the core of heavier elements is. Why else would such a big planet not become a star? A lack of hydrogen? That is the only other thing I can think of.
14 Dec 21
@Metal-Brain
The iron would remain intact because that is fusion poop. Iron is the leftover after fusion takes place.
Iron is star poop.
It is right in the place on the periodic table that says you get nothing from either fusion or fission, it is the dead end of star fusion. Useful dead end for sure🙂
15 Dec 21
@sonhouse saidI like iron. I think iron is cool. I once got to touch this big 10 ton meteorite with my bare hands; it resembled Swiss cheese and was the most beautiful piece of pure iron I've ever seen.
@Metal-Brain
The iron would remain intact because that is fusion poop. Iron is the leftover after fusion takes place.
Iron is star poop.
It is right in the place on the periodic table that says you get nothing from either fusion or fission, it is the dead end of star fusion. Useful dead end for sure🙂
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15 Dec 21
@sonhouse saidI never thought of it that way before, but I will from now on!
@Metal-Brain
The iron would remain intact because that is fusion poop. Iron is the leftover after fusion takes place.
Iron is star poop.
It is right in the place on the periodic table that says you get nothing from either fusion or fission, it is the dead end of star fusion. Useful dead end for sure🙂
"Iron is star poop."
Hell of a thought!
15 Dec 21
@sonhouse saidNot really. Supernovas are stars too.
@Metal-Brain
The iron would remain intact because that is fusion poop. Iron is the leftover after fusion takes place.
Iron is star poop.
It is right in the place on the periodic table that says you get nothing from either fusion or fission, it is the dead end of star fusion. Useful dead end for sure🙂
https://phys.org/news/2019-06-earth-heavy-metals-result-supernova.html
You mean smaller stars, not the big ones that can go nova.
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15 Dec 21
@metal-brain saidNo, they're not. Supernovas were stars, up to the point where they go supernova. It's only at that point, in the explosion, that the super-heavy elements are produced, not before using normal fusion. And once that happens, you no longer have a star, but a cloud of star remains.
Not really. Supernovas are stars too.
Of course, these remains may then contract under gravity again to form a new star system; but then, the super-heavy materials will form the planets, not the new star itself.
15 Dec 21
@shallow-blue saidHow long does a supernova last? It is not a fleeting moment. It is more complicated than you assert.
No, they're not. Supernovas were stars, up to the point where they go supernova. It's only at that point, in the explosion, that the super-heavy elements are produced, not before using normal fusion. And once that happens, you no longer have a star, but a cloud of star remains.
Of course, these remains may then contract under gravity again to form a new star system; but then, the super-heavy materials will form the planets, not the new star itself.