Poor old Jupiter has had a rough childhood after getting a massive hit from a mega-Earth Jupiter may have started life as a dense rocky planet that only became more gas-like after a massive newborn planet smashed right into it 4.5 billion years ago, according to new research. The paper, published in Nature on Wednesday, describes the scenario. A giant planetary embryo ten times as massive as the Earth, crashed …
It turns out Juno is the orbiter that produced these measurements. I had to read it in Ars Technica.
There was an episode of Dr Who where they went back to the formation of the solar system, opened the Tardis doors and watched the solar system form & develop at high speed.
With all these theories of planetary billiards, I'd love to sit and watch the formation of the solar system. It could be awesome viewing.
I did some simulations many years ago and you could get some interesting results in a couple of days of 200MHz Pentiums. I imagine now with GPUs and the like you could get some rather spectacular simulations done, The one thing I thought I learned at the time was you really have to assume a relatively uniform disk at the start or all bets are off.
Anyone know of any current modelling software for this?
Another possibility is that, when the core was massive, it had sufficient fissionable material to start a nuclear reaction that pushed the material apart again. This could be an ongoing thing: Fissionable materials collect the centre, react, disperse, collect again, and so on.
I have absolutely no evidence for this theory, though.
For a planet/body to ignite to turn into a star, it's more about the mass & density it has, rather than what it's made up of.
It's a bit of both. Yes, you need enough mass / gravity to produce the pressures required to initiate the nuclear fusion reaction, but you also need enough hydrogen at or near the core to provide the fuel.
Nuclear fusion of elements heavier than hydrogen only happens naturally in stars, when hydrogen fuel exhaustion allows gravitational collapse of a star's hot core, producing the enormous temperatures and pressures required to initiate fusion of heavier elements such as helium, carbon, oxygen etc.
If you replace fission with fusion, then what you're describing is how all stars work. It's called hydrostatic equilibrium: the heat rushing outwards balances gravity pressing inwards.
But Jupiter is not heavy enough to do this. (And it's unlikely it ever has been.) But it's slowly shrinking and those contractions are converted into heat enabling it to emit more "light" than it receives.
The other responses have been about fusion, which of course Jupiter is too small for. But the OP was about fission. Fission still occurs in the Earth, and is the source of the heat flow from the interior; this heat flow powers plate tectonics, in the sense that it causes melting.
The supply of fissionable isotopes was much higher in the early solar system, since most of those isotopes with relatively short half lives have by now fissioned away (with the exception of some that are themselves products of fission of longer-lived isotopes, like radon). So presumably the heat production due to fission (not fusion) was much higher in the planets of the early solar system.
Give that, plus the fact that massive planets might be more effective at separating out heavy elements--rather like a centrifuge (with heavier elements being more likely to be fissionable), your idea does seem plausible to me. But I'm no geophysicist...
@Torebn Mogensen: Nah. there wouldn't be enough energy to do that against that much gravity.
Also, even if enough fisionables collected in one spot to go boom, let alone create heat a la Oklo reactor, that'd have negligible effect on a Jupiter sized object even if there were hundreds of thousands of such happening all at once (highly unlikely).
To create the sort of effect you have in mind would need such huge concentrations of such rare material coming into close proximity at the same time in such a precise manner that, in essence it's highly unlikely to ever occur naturally during large multiple of the universe's current lifespan.
As for "it's the aliens wot dunnit" theories - if they had the capability to arrange that sort of thing, I can;t think of any reason why they'd want to do so - building a Dyson swarm instead would be a better use of their time and effort. Of course, if the sacred tome of HHGTTG actually is correct, then it might've been one of Slartibartfast's chums on the piss wot dunnit.
According to the paper, that would fall under "planetesimal enrichment and vaporization" and the verdict is "...relevant models typically cannot produce an extended diluted core [as is seen in Jupiter and, to a lesser extent, Saturn]."
Translation: proto-planets would have disintegrated, and their metals sunk to the centre and been deposited on a conventional rocky core. (Think growing salt crystals.)
Whereas Jupiter's core hasn't fully condensed into a solid lump. (Although it might do eventually.) And the authors' model model suggests a head-on collision that happened at a very late stage in planet formation would produce that.
Is it not also just as likely some pressure/fluid/heat dynamics is spreading things about too. I mean, it has super diamonds and metallic hydrogen. For certain, there are still uncertainties of the exact mechanics at the size and densities of what we get with Jupiter... so saying it's most likely a (unprovable/testable past event) planetary collision is all well and good... but how do we know it's the "better" theory compared to any other?
but how do we know it's the "better" theory compared to any other?
We don't. Until a theory is proven valid*, it's just a guess and there's lots of guesses about Jupiter.
*Some guesses are probably just too improbable to be real. Reference the post above about 'Ron".
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I think the best analogy is the night that Sven's wife called him on the cell on his commute home. Lena said, "Now Sven, you be careful out dere. The news says dere's somevun driving de wrong vay on de freevay." Sven replies, "Ya, sure, if dere's one, dere's a tousant."
I propose that we name whatever hit proto-Jupiter and proto-Earth, Sven.
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