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posted by martyb on Wednesday October 25 2017, @02:09AM   Printer-friendly
from the Cosmic-Play-Doh® dept.

http://jhuapl.edu/newscenter/pressreleases/2017/171019.asp

Narrow dense rings of comets are coming together to form planets on the outskirts of at least three distant solar systems, astronomers have found in data from a pair of NASA telescopes.

Estimating the mass of these rings from the amount of light they reflect shows that each of these developing planets is at least the size of a few Earths, according to Carey Lisse, a planetary scientist at the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Maryland.

Over the past few decades, using powerful NASA observatories such as the Infrared Telescope Facility in Hawaii and the Spitzer Space Telescope, scientists have found a number of young debris disk systems with thin but bright outer rings composed of comet-like bodies at 75 to 200 astronomical units from their parent stars — about two to seven times the distance of Pluto from our own Sun. The composition of the material in these rings varies from ice-rich (seen in the Fomalhaut and HD 32297 systems) to ice-depleted but carbon rich (the HR 4796A system).

[...] In Fomalhaut and HD 32297, researchers expect that millions of comets are contributing to form the cores of ice giant planets like Uranus and Neptune — although without the thick atmospheres enveloping the cores of Uranus and Neptune, since the primordial gas disks that would form such atmospheres are gone. In HR 4796A, with its warmer dust ring, even the ices normally found in the rings' comets evaporated over the last million years or so, leaving behind core building blocks that are rich only in leftover carbon and rocky materials. "These systems appear to be building planets we don't see in our solar system — large multi-Earth mass ones with variable amounts of ice, rock and refractory organics," Lisse said. "This is very much like the predicted recipe for the super-Earths seen in abundance in the Kepler planet survey."

The supposed exoplanets could also be called "massive solid planets" or "mega-Earths".

Accretion of Uranus and Neptune from inward-migrating planetary embryos blocked by Jupiter and Saturn

Infrared Spectroscopy of HR 4796A's Bright Outer Cometary Ring + Tenuous Inner Hot Dust Cloud


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  • (Score: 3, Interesting) by Fluffeh on Wednesday October 25 2017, @03:49AM (3 children)

    by Fluffeh (954) Subscriber Badge on Wednesday October 25 2017, @03:49AM (#587255) Journal

    On the surface perhaps, but if they have molten cores and vulcanism then there should be plenty of opportunities for life beneath.

    Actually, although this sort of volcanic activity can lead to simple life - it is unlikely to create more complex life as the energy density (availability) is not high enough.

    Here's an interesting paper if you want to do some extra reading: http://www.pnas.org/content/111/35/12628.full [pnas.org]

    Here's a section that talks about energy density:

    Energy. Energy for life can come from chemical redox couples generated by geothermal processes or light from the central star. Geothermal flux can arise from (i) the planet cooling off from its gravitational heat of formation, (ii) decay of long-lived radioactive elements, or (iii) tidal heating for a close-orbiting world or moon. Note that on Earth only a tiny fraction of the geothermal heat is converted into chemical energy, whereas about half the solar flux occurs at wavelengths that are usable for photosynthesis
    ...
    Life based on geothermally derived chemical energy would, by dint of energy restrictions, always remain small and globally insignificant.

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  • (Score: 2) by Arik on Wednesday October 25 2017, @04:07AM (2 children)

    by Arik (4543) on Wednesday October 25 2017, @04:07AM (#587258) Journal
    Life tends to follow the easiest path to survival, and photosynthesis is easier here, so that's what it does. But if it became impossible overnight life would continue. Also it stands to reason that geothermal energy would be considerably greater on a planet as under discussion - earth-like in composition, but several times larger. It might well be less likely for intelligent life to evolve on such a planet, but I am not convinced that's necessarily true, and even if it that may not mean so much if they are very common.
    --
    If laughter is the best medicine, who are the best doctors?
    • (Score: 2) by Fluffeh on Wednesday October 25 2017, @04:43AM (1 child)

      by Fluffeh (954) Subscriber Badge on Wednesday October 25 2017, @04:43AM (#587266) Journal

      It might well be less likely for intelligent life to evolve on such a planet, but I am not convinced that's necessarily true

      Certain parts of the body require a LOT of energy to function. Our brains, as small as they are compared to the rest of the body account for about 20% of the total energy we use. Additionally, while it can be theorized that with a smaller amount of energy to use, evolution creates life that uses it sparingly (such as animals that move slower for example - like the Sloth) - but it just makes it less likely.

      I'm not saying it is impossible - if the universe is infinite, then it's certainly happening somewhere, just the chances of it happening in a particular place is small.

      The other thing you need to think about from a biological point of view, is that there are vast amounts of various extremophiles here on earth - all manner of things that lives in amazing environments from ultra saline water to radioactive bars in reactors - but these have ADAPTED from life that already existed. If you had a planet where the ONLY environment was plutonium bars in water, the those things just wouldn't pop into existence one day. You have to have a certain set of conditions for the super primitive life to get a start, then you can wind up the difficulty levels so to speak.

      • (Score: 2) by Arik on Wednesday October 25 2017, @05:41AM

        by Arik (4543) on Wednesday October 25 2017, @05:41AM (#587282) Journal
        I'm not sure why you think the sloth is any less likely than we are.

        Anyway my point wasn't about the likelihood but about the shape it might take, and I do like that sloth idea.

        Perhaps small sloth-like beings, with dense muscles and opposable thumbs, for climbing in lava vents rather than trees so I imagine thickly padded palms. Perhaps with heads of Organian proportions.
        --
        If laughter is the best medicine, who are the best doctors?