Are Small Rocky Worlds Naked Gas Giants? 91
astroengine writes "The 'core accretion' model for planetary creation has been challenged (or, at least, modified) by a new theory from University of Leicester astrophysicists Seung-Hoon Cha and Sergei Nayakshin (abstract). Rather than small rocky worlds being built 'bottom-up' (i.e. the size of a planet depends on the amount of material available), perhaps they were once the cores of massive gas giant planets that had their thick atmospheres stripped after drifting too close to their parent stars? This 'top-down' mechanism may also help explain how smaller worlds were formed far from their stars only to drift inward toward the habitable zone."
Well then... (Score:2, Funny)
I imagine this excludes Earth, but if not it would explain a lot of the smells.
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considering we went from being stuck on to the ground to getting in space within a lifetime, i wouldn't write off long distance space travel just yet.
outlook doesn't really look that great though..
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Stop eating at cheesy Mexican restaurants and stop tipping the cows. That'll solve the problem for all of us.
Re:Well then... (Score:4, Funny)
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Yo mamma is so fat that she was mistaken for a naked gas giant!
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Slashdot always had stupid, juvenile humor mixed in with the more sophisticated gems, obscure sci-fi references, jokes in psuedo-code, and occasional guy who actually has some experience with the subject at hand. Perhaps you are just getting older?
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its not that those things aren't around anymore.. its the amount of crap you have to wade through to get to the goods that seems to be increasing.
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Well, that "theory" is wrong. A gas giant at Earth's orbit would retain its entire atmosphere. Pluto, well, not a gas giant?
It's not even a hypothesis.
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Pluto isn't even a planet any more :(
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We are no improved monkeys. Every species living today is the pinnacle of its own evolution. Our minds and civilisation are a glitch, a side product, not a evolutionary goal. The only goal of evolution is survival and reproduction.
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I'd bet that most of the time, "monkeys" is used instead of "primates" because of the derision that started around the time of the Scopes Monkey Trial, and the nomenclature stuck.
Wait a tic... (Score:2)
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That's what you get for not publishing your idea in a peer-reviewed science journal! Stupid 3rd graders.
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No, that's what he gets for not recognizing the fundamental difference between a 'rocky world' and a small ball of ice.
Hot Jupiters? (Score:4, Insightful)
For a long time the only planets we found were 'hot Jupiters'. Jupiter sized planets very close to their star (inside Mercury's orbit).
Why weren't these planets stripped of their atmosphere?
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For a long time the only planets we found were 'hot Jupiters'. Jupiter sized planets very close to their star (inside Mercury's orbit).
Why weren't these planets stripped of their atmosphere?
Because nobody's there to sing "You can leave your hat on"?
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For a long time the only planets we found were 'hot Jupiters'. Jupiter sized planets very close to their star (inside Mercury's orbit).
Why weren't these planets stripped of their atmosphere?
Because nobody's there to sing "You can leave your hat on"?
From a quick perusal of the article, one group of sentences stands out:
"The final fate of the clumps and thus the outcome of the simulation in its entirety does depend on the cooling prescription (as also expected based on analytical models of Nayakshin 2010c,b,a), initial conditions, e.g., the disc mass, and missing physics (e.g., exact radiative transfer, and a better opacity, dust growth and fragmentation models) not yet included into the code. If radiative cooling of clumps is not suppressed suffici
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I think the general idea is that these would in fact be proto-planets. Essentially any of these gas giants rotating close to their suns could evolve into an Earth like planet. The question would be how old are the systems that we are finding these gas giants close to their stars? If they are all old systems then I doubt the theory will hold up. If they are mainly younger systems then it's possible. There has to be more than one way for planets and moons to form if this theory is true because the theory wou
Re:Hot Jupiters? (Score:4, Informative)
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IANAA (astronomer), but it seems that the thrust of the article is on the homogeneous formation of protoplanets from gas and dust and their migration to stable positions rather than the stripping of atmospheres from gas giants. In fact, "stripped" gas giants have been theorized for quite some time and are referred to as "chthonian planets [arxiv.org]."
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General history of the universe is that each galaxy starts out as super-massive red giants which rapidly burn up their fuel and explode, forming new but smaller stars. Eventually the remains reform into stars and planets.
I guess the iron from the fusion process and the heavier elements from the supernova process would end up forming the new stars and planets.
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like whats found in the center of (almost?) every galaxy? yes, yes indeed... not all that matter gets turned into a black hole though, the left overs get turned into stars & planets.
Re:Hot Jupiters? (Score:4, Informative)
RTFA (A=abstract, since the article is behind a paywall)
Never fear, arXiv delivers: http://arxiv.org/abs/1010.1489 [arxiv.org]
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For a long time the only planets we found were 'hot Jupiters'. Jupiter sized planets very close to their star (inside Mercury's orbit).
Why weren't these planets stripped of their atmosphere?
Because those are young planetary systems? Just like ours was some 4.5 billion (give or take) years ago. Sounds like a reasonable guess.
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Your guess is wrong.
Magnetic field of planets keeps their atmosphere in place, to some extent. Basically, it prevents ionized gases from escaping. Without a magnetic field, Earth would be like Mars, lifeless and almost without atmosphere. It is believed that Mars lost its atmosphere when its magnetic field disappeared.
For light elements, like H or He, you need much stronger gravitational force to keep the non-ionized molecules down. Something like Jupiter.
This brings us back to Jupiter. Jupiter is well with
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Magnetic field of planets keeps their atmosphere in place, to some extent. Basically, it prevents ionized gases from escaping. Without a magnetic field, Earth would be like Mars, lifeless and almost without atmosphere. It is believed that Mars lost its atmosphere when its magnetic field disappeared.
We
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Why weren't these planets stripped of their atmosphere?
Some of them quite clearly are being stripped, undergoing significant mass loss as their stars blast away at their atmosphere. Remember, for most everything you look at, it is not in its end-state.
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The reason we only found hot Jupiters for a long time is because those are by far the easiest to discover. It doesn't mean there are more hot Jupiters than earth-like planets. It simply means we did not have the precision yet to see the earth-like planets. When we looked at a star, we either saw a hot Jupiter, or we saw nothing. Anything smaller or further away than a hot Jupiter did not cause enough wobble in the parent star to notice.
Wait a minute... (Score:2)
modified > challenged
no?
What about all these new gas giants? (Score:2)
Many of these extrasolar gas giants are in extremely small orbits very close to a star. So how could Earth and Mars have lost huge atmospheres?
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Is that sail or sale? Or is that a sail sale? I suppose you can hold a sale around Neptune in a submarine having fun on Triton, especially if something like the Battleship Yamato [wikipedia.org] actually makes the trip into space. If a battleship can do that, I suppose a submarine can too.
I also suppose these "scientists" haven't been able to really prove the existence of China to your satisfaction either. Yes, Marco Polo brought back some amazing legendary stories and a few trinkets he claims to have come from there.
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They can't really prove there is a distant planet revolving around a distant world.
You seem to have bought the 'distant world' theory, you're this close in believing the earth isn't flat. Do your parents know this?
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Continuing Gas Giants remark... (Score:3)
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Richie, eat your crust!
Are Small Rocky Worlds Naked Gas Giants? (Score:2, Redundant)
Re:Trivial? (Score:5, Interesting)
How does this square with the idea that gas giants have materials like metallic hydrogen at their cores? I can see how accretion can occur without the necessity for a rocky core, and I can see how it would occur with one.
There isn't necessarily a dilemma here as the theory still can be consistent for both results, in terms of rocky "terrestrial" bodies being naked gas giants and "traditional" gas giants still having a metallic hydrogen core.
Planets like Jupiter and Saturn, while certainly the bulk of their current mass is Hydrogen and Helium, they do have other elements that comprise their structure and more than likely you would find at the core of these planets a "rocky" core that would include Iron, Nickle, and other elements that would be more identifiable with what we have here on the Earth. The question would be how large would that tiny "rocky" core would be if you stripped off the outer gaseous layers.
The problem with this theory is mainly how you go about stripping off that outer layer. The presumption here is that objects close in to a star like the Earth, Mars, and Venus are at the moment would have had this outer "shell" being stripped off at some point in the distant past as the Solar System was being formed.
Highly unlikely theory (Score:5, Interesting)
As this calculation for CoRoT-2b [slashdot.org] indicates, at 6M tons per second, a hot super-Jupiter would need more than 39B years (~3x the age of the universes) to be "blown/boiled away". Jupiter is ~1/3 the mass of CoRoT-2b, so at 6MT/s, it would last 13B years. The rate of loss of atmosphere would have to be at least a factor of 10 greater than on CoRoT-2b, or greater than 60MT/s just for a Jupiter mass planet to to reach an Earth mass core in 1.3B years. Our solar system is estimated to be ~5B years old and that Earth and Mars both appear to have been rocky for more than 2B years, so 1.3B years to blow off an atmosphere seems to be a generous estimate of quickly it must have happened.
Given that our sun is only converting ~600M tons/sec of hydrogen into ~594M tons of helium, a net loss of 6MT/s, therefore a Jupiter mass planet would need to be receiving a enough of the solar radiation to blow off 60MT/s. Yes, E=mc^2, and c^2 is large, but you're still talking about a lot of mass to move out of notable gravity well (first out of the Sun's gravity well, then move more mass out of Jupiter's gravity well). If jupiter were in earth's orbit, would it receive enough solar radiation to lose 60MT/s? Not from solar wind, the total solar wind [wikipedia.org] mass is ~1.85MT/s. even if all 1.8MT were directed at Jupiter and Jupiter had no magnetopause to protect it from the solar wind, 1.8MT/s would not strip 60MT/s of atmosphere. So you have to come up with a theory where the EM radiation causes the the planet to eject it's own atmosphere, which is still going to be virtually impossible [wikipedia.org].
Re:Highly unlikely theory (Score:5, Interesting)
The Sun (Sol in Latin and derivative languages) is more like a 3rd or 4th generation star in terms of material recycled from previous stars that has gone through supernovas and reformed to become new stars. At least that is where exotic elements like Uranium, Gold, Silver, and just about everything heavier than Oxygen have come from.
I presume the objection here is that 1st generation stars (which at this point are very old stars which likely have had any planets around them ripped off simply by passing near other stars on any journey they have made going around the galactic core or even a small globular cluster) would behave differently than something you would see around the Sun. Certainly compounds more exotic than water would be quite rare and even water would be minor.
Still, of the planets that are being considered with this model, I think the GP post is fairly on spot in terms of skepticism on this theory. EM radiation alone is unlikely to be able to provide the energy needed to strip gas giants of their atmosphere, where I think you would need some kind of gravitational actor as well. The problem with that theory is it introduces a 3-body problem and requires an explanation for where that object went, whatever it was. The 3-body problem is a big deal because at the very least any planet would likely be in a highly elliptical orbit where the presence of that gravitational anomaly would leave some evidence behind. I don't think that is necessarily a good idea either.
The environment in a stellar nursery would be rather complex, where perhaps a "nearby" neutron star emitting x-rays and other complex aspects of the environment might also be a factor. The ignition sequence of what happens with a star finally starts the fusion process could also be a factor here, where there might be some added complexity in the protostar cloud before the star finally settles down into a stable main sequence pattern. A brief (on the scale of a typical star's lifetime) period of intense radiation and/or stellar wind when this ignition starts might be something to consider. Current theory suggest this is a rather benign event where gravity merely starts compressing the gasses that gradually start producing more fusion before it becomes stable, but that might be mistaken. For small stars (stellar class M objects, for instance) that may be the case, but larger stars certainly do have their own peculiar life cycles anyway so the "birth" of a large star might be nearly as dramatic as its death, just as the death of class M stars is rather wimpy too.
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The gravitational forces alone on Jupiter are more than enough to hang onto the full atmosphere it currently holds, even if it were at the position that the Earth is at. Yes, even if Jupiter was "heated" to the temperatures that we find on Earth today from solar flux radiation, the Hydrogen gas would do just fine. Some would be pulled off due to solar wind and increased thermal pressure, but it would take the lifetime of the Universe before it would be something you would notice.
It is for this reason I wa
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At least that is where exotic elements like Uranium, Gold, Silver, and just about everything heavier than Oxygen have come from.
Agree with everything else you said -- but it's Iron, not Oxygen, that is the heaviest element that can be created through stellar fusion processes.
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Oxygen is about the heaviest element that was left over from the Big Bang in any substantial quantity, which is what I was referring to. Most of the heavier elements like even Carbon or Sodium needed nuclear fusion processes in order to form them in the quantities we see in the Solar System today.
Yes, I do realize that Iron is at the "bottom" of the fusion well in terms of what element starts supernovas. Perhaps I should have made that more clear what I was trying to suggest here. Likely nearly every ele
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Re:Highly unlikely theory (Score:5, Informative)
I read the article and the abstract. Apparently you failed to comprehend it, go read it again. They talk about stripping the atmosphere/gases from a 7.5 Earth Mass (Me) clump at ~8 AU. So, my example still applies. The details may vary a bit, but a 7.5Me clump is going to have a significant gravity well/escape velocity, and for it to absorb enough solar radiation @ ~8 AU is beyond unbelievable, the math just doesn't work.
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Since a super-Jupiter would probably have a higher escape velocity than Jupiter, it might be easier to strip atmosphere from Jupiter than from a super-jupiter. Also, I'm assuming that solar wind that hits a gas giant dead on probably results in net absorption rather than net loss of atmosphere and that most of the loss occurs where the solar wind hits the sphere of the planet at a tangent. Jupiter does, presumably (unless the material is very much denser), have a smaller circumference than a super-jupiter,
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. Jupiter does, presumably (unless the material is very much denser), have a smaller circumference than a super-jupiter, so that might slow the loss by a bit.
The circumferences will be about the same. Around the mass of Jupiter, the extra gravity from more material balances out the volume of the extra material. Gliese 229B has 20 to 50 times the mass of Jupiter, but around the same size.
Inside a gas giant (Score:1)
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I thought the solid surfaces of gas giants weren't rocky at all, but rather hydrogen compressed to a metallic state under extreme pressure? Without the pressure, the gas would melt and then boil away.
At the surface, that's probably true. It does not contradict the notion, still generally held to be true, that there's a rocky core underneath that.
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I thought the solid surfaces of gas giants weren't rocky at all, but rather hydrogen compressed to a metallic state under extreme pressure? Without the pressure, the gas would melt and then boil away.
At the surface, that's probably true. It does not contradict the notion, still generally held to be true, that there's a rocky core underneath that.
Both you and the GP's notions are based on speculation an computer modeling. The Juno craft will soon be leaving for Jupiter, and hopefully will help us understand what really is at the core.
I once met a naked gas giant! (Score:2, Funny)
Diamonds, Garnets, and Granulites? (Score:2)
At those pressures, we ought to see a planet covered in diamonds, garnets, granulites, etc. - very high temperature metamorphic rocks. If the planet is made of other types of rock, then there probably wasn't that much pressure on it when the rock formed.
Disclaimer: I am not a xenogeologist.
Are ALL small rocky worlds naked gas giants..? (Score:1)
This seems to be the title of this post. Very unlikely don't you think. Are some? Sure, why not.
The general rule of thumb is that volatiles like water/hydrocarbons/helium get evaporated and blown out by the nascent star at the centre of a proto-planetary disk. So, many rocky planets will form from the remaining silicate and other non-volatile materials (such as Iron) that are left after most of the volatiles are gone. Will some gas giants migrate inwards and have their atmospheres evaporated and blown off..
SMTS (Score:1)
undersized stars (Score:2)
Gas giants are wannabe stars. They are Pauly Shores of the night skies.
Earth could be considered a Gas Giant (Score:2)
The Earth surrounded by Oxygen gas (and other gases) in the atmosphere, the only difference to us is that our eyes have evolved to see through the wavelength of oxygen making it appear 'invisible', but from the hypothetical alien point of view, an alien looking at earth might not have the eyes to see through the Oxygen and it would look like any other gassy planet from their perspective.
Maybe the technology can be developed to look through the gasses of other planets to see inside in the same way we can see
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Nice theory, but no... at least with regards to your alien concept.
A substance is considered opaque when light does not pass through it.
Light *DOES* pass through our atmosphere. It is translucent to many frequencies (heck, it's even translucent to visible light), and it absorbs many others. I do not think it actually reflects any EM frequencies, however, except those that hit it at a sufficient angle to be totally reflected due to its index of refraction.. To an alien whose eyes could only see in s
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Half an explanation (Score:2)
perhaps they were once the cores of massive gas giant planets that had their thick atmospheres stripped after drifting too close to their parent stars?
(emphasis mine)
Let's assume they did. How did they drift back out?
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Of course! (Score:3)
Eureka moment....here is what I believe, if the clouds are like the cocoon of a moth, helping keep it safe until it transforms, then you could almost say that the cloud is there for a reason, and that the planet is now morphing into a solid planet ready for life. This would imply that the gas is great vs. anything damaging to a planet while forming....such as cosmic or gamma rays, solar winds, UV rays etc...whatever that might be ....we can also deduce that if the gas planets are the precursors to
formed planets...then we can assume there is an evolutionary path that forces the gas inside to condense while the gas outside stays there for protection...leading to believe that there are 2 types of gas...one for creation of , and one for defense....
Now that we know this, I think if we were to use that same information and look into the defense properties of that second gas, in order to define what it is made up of, and maybe replicate that someway for our development of mars, in essence helping the mars rock to become habitable (again or for the first time?) ...
it might help us create a second rock that can hold human life.
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Not to mention that cocoons were an evo
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>This is not due to some cosmic evolution whose purpose is to create life on a planet.
This is based on proof or theory , as most people tend to forget that ALL space information (that has not been found to be truth) is still just theory.
If someone were to say that planets are actually alive, and that they were beings, you would say...what?
However, consider the mechanisms that planets harboring life has in order to maintain its stability, sort of like defense mechanisms if you will, then you could say tha
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With your said analogy of a planet, technically we would not be considered alive either....if all we are is a bunch of atoms strung together and
kept in a particular state by a beating heart some lungs to provide oxygen, and maybe a stomach to digest food to provide fuel to continue
existing, then of course the planet is not alive, we are not alive etc...
However, if you consider the fact that an animal is alive as much as a human, even though they do not share the same type of intelligence seeing as they do n