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Space Science

Are Small Rocky Worlds Naked Gas Giants? 91

Posted by Soulskill
from the elliptical-streaking dept.
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."
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Are Small Rocky Worlds Naked Gas Giants?

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  • by reeno49 (1558221)

    I imagine this excludes Earth, but if not it would explain a lot of the smells.

    • by macraig (621737)

      Stop eating at cheesy Mexican restaurants and stop tipping the cows. That'll solve the problem for all of us.

    • by Penguinshit (591885) on Saturday September 17, 2011 @09:02PM (#37431658) Homepage Journal
      I once sat next to a gas giant on an airplane. Thank God it was just a short commuter flight.
    • by dkleinsc (563838)

      Yo mamma is so fat that she was mistaken for a naked gas giant!

  • I've had this idea before. Thought that's what happened to Pluto, when I was was in 3rd grade. I don't see anyone nominating me for a Nobel prize!
    • Re: (Score:3, Funny)

      by Anonymous Coward

      That's what you get for not publishing your idea in a peer-reviewed science journal! Stupid 3rd graders.

      • 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)

    by clonan (64380) on Saturday September 17, 2011 @07:13PM (#37431306)

    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?

    • by c0lo (1497653)

      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"?

      • 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

    • Re: (Score:3, Interesting)

      by Anonymous Coward

      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)

      by GreenTom (1352587) on Saturday September 17, 2011 @07:36PM (#37431402)
      RTFA (A=abstract, since the article is behind a paywall)...the abstract doesn't say that gas giants formed, then were stripped. It suggests the protoplanatary disk breaks up into clumps of gas and dust, and that the clumps that come too close to the star are stripped of their gas. I think all this happens long before the dust clouds condense into planets. At least from the abstract, all they seem to be saying is that the same original dust clouds could become rocky planets or gas giants, depending on if they're disrupted or not.
      • by Anonymous Coward

        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]."

      • by mikael (484)

        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.

      • Re:Hot Jupiters? (Score:4, Informative)

        by arcctgx (607542) on Saturday September 17, 2011 @09:05PM (#37431674)

        RTFA (A=abstract, since the article is behind a paywall)

        Never fear, arXiv delivers: http://arxiv.org/abs/1010.1489 [arxiv.org]

    • by Holammer (1217422)

      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.

      • by Anonymous Coward

        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

        • by dryeo (100693)

          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

    • An explanation compatible with this new idea would be they may planets in a system not be old enough for the process to have completed.
    • by osu-neko (2604)

      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.

    • by Anonymous Coward

      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.

  • modified > challenged

    no?

  • 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?

  • by fuzzyfuzzyfungus (1223518) on Saturday September 17, 2011 @07:50PM (#37431448) Journal
    Your crust is showing. Slut.
  • I don't know. Why ask me? What on Earth makes you think I would know? Go ask an expert. Geesh.
  • by gstrickler (920733) on Saturday September 17, 2011 @08:19PM (#37431530)

    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].

    • by tragedy (27079)

      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,

      • by sFurbo (1361249)

        . 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.

  • 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. I thought rocky planets were basically accretions of asteroid junk.
    • by osu-neko (2604)

      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.

      • 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.

  • Ah wait, it was just your mom.
  • 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.

  • 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..

  • Show me the simulation. It would make a nice screen saver and maybe explain the theory to those who haven't read TFA or imagined it previously.
  • Gas giants are wannabe stars. They are Pauly Shores of the night skies.

  • 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

    • by mark-t (151149)

      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

    • We can't see through the atmosphere of Venus, but that doesn't make Venus a gas giant. The atmospheres of Venus and Earth are extremely thin compared to the radius of the planets themselves, whereas Jupiter's atmosphere is bigger than its rocky core. Also by the way, Earth's atmosphere is mostly nitrogen.
  • 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?

    • by mark-t (151149)
      That phrase sort of had me puzzled as well.... planets don't just "drift"... they are in (relatively) stable orbits around their parent star, and it's my understanding that generally speaking, that's roughly where the planet is born - out of the matter in the accretion disc of the parent star that had a sufficient tangential velocity to the star to sustain an orbit at that distance.
  • by hesaigo999ca (786966) on Sunday September 18, 2011 @01:27PM (#37434674) Homepage Journal

    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.

    • And I would have to ask you how life would form when the rocky core is encased in a solid hydrogen shell. Not to mention once you have a gas giant close enough for its atmosphere to be stripped by its star, then you're pretty much a lost cause for developing life. Especially when the entire atmosphere has been stripped and all that is left is an airless world. This isn't like a gas giant being stripped of most of its atmosphere and leaving an Earthlike world behind.

      Not to mention that cocoons were an evo
      • >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

        • Correct, we are still learning about this field. However, you are erring in that you are treating a planet like it is a living entity rather than what it really is. The planet isn't having any trouble at all in maintaining itself due to our existence. What is having trouble maintaining itself is the complex balance or ecosystems which reside ON this planet. The fact that Earth has oceans and land and a favorable atmosphere does not in any way suggest that the planet itself is alive or predisposed toward mak
          • 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

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