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posted by girlwhowaspluggedout on Monday March 10 2014, @12:01AM   Printer-friendly
from the who-keeps-atlantis-off-the-maps dept.

Papas Fritas writes:

"Ian O'Neill writes in Discovery Magazine that despite NASA's best efforts to track it down, there is no evidence for the existence of Planet X. This hypothetical world that may or may not be orbiting the sun beyond the orbit of Pluto has inspired many a doomsday theory. In the run-up to the much anticipated "Mayan Doomsday" of December 21, 2012, the marauding Planet X was scheduled to make a inner-solar system dash, sparking gravitational mayhem and triggering civilization-ending solar flares.

But in spite of the doomsday nonsense, the hunt for "Planet X" actually has roots in real science. In the mid- to late-19th Century, astronomers were tracking the gravitational perturbations of the gas giant planets in an effort to track down an undiscovered world in the outermost reaches of the solar system. This hypothetical massive planet was dubbed "Planet X." However, this fascinating trail ended with the discovery of tiny Pluto in 1930. The idea that the sun may have a stellar partner has also been investigated, perhaps there's a brown dwarf going unnoticed out there. Nicknamed "Nemesis," this binary partner could be evading detection. One strong piece of evidence laid in the discovery of the "Kuiper Cliff," a sudden drop-off of Kuiper Belt objects in the region just beyond Pluto. Could the Cliff be caused by a previously overlooked world? Also, geological record has suggested there's a regularity to mass extinctions on Earth linked to comet impacts. Could a distant orbiting body be perturbing comets, sending them our way on a cyclical basis?

However, the Center for Exoplanets and Habitable Worlds at Penn State University has analyzed data from NASA's Wide-Field Infrared Survey Explorer (WISE), a space telescope that carried out a detailed infrared survey of the entire sky from 2010 to 2011. If something big is lurking out there, WISE would easily have spotted it. According to a NASA news release, "no object the size of Saturn or larger exists out to a distance of 10,000 astronomical units (AU), and no object larger than Jupiter exists out to 26,000 AU. One astronomical unit equals 93 million miles. Earth is 1 AU, and Pluto about 40 AU, from the sun." Observations by WISE have also ruled out the Planet X Comet Perturbation theory.

 
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  • (Score: 5, Insightful) by melikamp on Monday March 10 2014, @01:37AM

    by melikamp (1886) on Monday March 10 2014, @01:37AM (#13710) Journal

    I wish someone with the requisite knowledge would explain why planets are assumed to be hot enough to be detectable. Is it possible that a planet which condensed out of the primordial hydrogen-helium soup has nothing to fuse, and is really really cold by now?

    Call me crazy, but I think it is reasonable to suppose that the frequency of objects is correlated (probably not linearly) with their sizes. The Solar system provides plenty of anecdotal evidence, with 1 star, 4 giants, 19 bodies comparable in size with Earth (down to .1 Earth radius), hundreds of objects comparable to Sharon and Sedna (0.1-0.01 Re), and it just keeps going like that all the way to the microscopic dust. On the galactic scale, red dwarfs are way more populous than all the heavier stars put together, and all but two of the 50+ local group members are tiny disturbed galaxies. So I think the interstellar space may well be littered with stray planets, and if it's not, then we have a really interesting problem on our hands.

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  • (Score: 2, Insightful) by BradTheGeek on Monday March 10 2014, @02:20AM

    by BradTheGeek (450) on Monday March 10 2014, @02:20AM (#13717)

    Even of the mass is too low to fuse, there is still heating from gravitational effects. One has only to look at the other gas giants to see that. Even if that heating and subsequent emission is low, it should be visible in the infrared, especially with the sensitivity of detectors available to us now.

  • (Score: 1) by morgauxo on Monday March 10 2014, @03:00PM

    by morgauxo (2082) on Monday March 10 2014, @03:00PM (#14006)

    "Is it possible that a planet which condensed out of the primordial hydrogen-helium soup has nothing to fuse"

    Hmm... well, anything made of hydrogen certainly has something to fuse! Hydrogen is the easiest element to fuse!

    But... no planet is ever going to fuse hydrogen (or anything else). Why? By Definition! If it were large enough to have enough pressure to start fusion it wouldn't be a planet. It would be a star!

    However, large planets do still generate their own heat through other methods. We can see this in Jupiter and Saturn, gravitational effects make them hotter than just the energy they receive from the sun. The same should happen with any planet large enough to be the mythical planet X.

    What about small planets? Those don't count when you are talking about planet X. Planet X is a theoretical explanation for oddities in the orbit of Neptune and also for flinging comets towards Earth and causing periodic extinction events. This would require a large planet thus it would be self-warming.

    • (Score: 4, Informative) by VLM on Monday March 10 2014, @03:34PM

      by VLM (445) Subscriber Badge on Monday March 10 2014, @03:34PM (#14022)

      "no planet is ever going to fuse hydrogen (or anything else)."

      Jupiter is a fairly effective deuterium fuser with plenty of fuel. You can google for all manner of astrophysics journal papers, its been heavily discussed. Lots of PHD and grad students working on this for a long time. Google for "jupiter excess heat" "jupiter anomalous heat" and similar topics. Jupiter seems likely to squirt out enough D-D fusion heat to explain its unusually high temp, and the rate is reasonable in that its got enough fuel to keep percolating along for like a hundred billion years so its calm and steady state.

      Much as you can make a tabletop device that operates way below breakeven, you can get planets in the same situation, cooking along way below breakeven, yet, still, none the less, slowly cooking. I believe breakeven for deuterium is like 1-2 dozen Jupiter masses and plain old P-P breakeven is around 75 Jupiter masses, certainly less than 100, but this is all from memory.

      For tabletop / lab size / planet or star size, there's no lightswitch below which there's no reaction and above which the rate goes infinite. The rate does scale pretty intensely with mass but its totally arbitrary with current knowledge to call 10 jupiter masses a planet and 15 a star, nothing magical happens just one is hotter than the other. Much like humans love to play name games WRT what is a planet vs a wanna-be planet.

      So yeah, Jupiter fuses plenty of deuterium, enough to raise its temp / heat emission and its measurable. Just not enough to ignite in a self sustaining "fire", not enough by a huge factor.

      Like trying to set soaking wet paper on fire. No a pile of wet newspaper mush won't self sustain burning. But if you hold a torch to it it'll slowly burn or even just sitting around it'll slowly decompose and oxidize. So saying wet paper "won't oxidize" is not correct, although its also true it won't burn like a blazing campfire.

    • (Score: 2) by melikamp on Monday March 10 2014, @04:39PM

      by melikamp (1886) on Monday March 10 2014, @04:39PM (#14081) Journal
      Bah, I meant fission, not fusion. But reading the follow-up discussion made things more clear to me :)