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B Luhman 16AB

  1. Jun 20, 2017 #1
    I have been reading up on the latest Hubble observations concerning the binary brown dwarf pair Luhman 16AB (officially WISE J104915.57-531906.1AB). It occurred to me that I did not know what to call the objects that most likely are in orbit around both brown dwarfs. Since brown dwarfs are more than a planet, but less than a star, neither moon nor planet seem to apply. I am not trying to be controversial, I honestly do not know the correct label for objects that obit brown dwarfs. Can anyone help me out?


    Luhman 16AB

    Recent sources I've been reading:
    Hubble Space Telescope astrometry of the closest brown dwarf binary system -- I. Overview and improved orbit - arXiv 1706.00657
    New Looks at Brown Dwarfs - Centauri Dreams, June 13, 2017
     
  2. jcsd
  3. Jun 20, 2017 #2

    Bandersnatch

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    'Satellites'?
     
  4. Jun 20, 2017 #3
    A quick glance through Google suggests that 'planet' is the most commonly used term.
     
  5. Jun 20, 2017 #4

    jim mcnamara

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    Staff: Mentor

    I tried the IAU: https://www.iau.org/public/themes/naming/#minorplanets
    This has the definition of minor planets, which those objects could well be. But I do not know for sure, either.

    I think IAU is supposed to have a complete sets of definitions.... So logically if it is a complete set of definitions, then one of them matches. Hmm.
     
  6. Jun 20, 2017 #5
    "Satellite" seems like as good of a generic term as any. At least it is an accurate description, without delving into what the object might be. Satellite could apply to anything that is in orbit.
     
  7. Jun 20, 2017 #6
    In this paper in nature they say "planet".

    Definition of a planet in the solar system:
    Definition of planets outside should be the similar. I believe the IAU does not have stance on the designation of any exoplanets. Any object large enough to be identified with current technology will also be large enough to form hydrostatic equilibrium and to clear the neighborhood. So it is an "exoplanet".
    A "minor planet" is too small to form hydrostatic equilibrium and is not a "comet". All things in the solar system held together by gravity are either "planet", "dwarf planet", "minor planet" or "comet".
     
  8. Jul 10, 2017 #7
    In a recent thread concerning the Brown Dwarf Minimum Mass I seem to have stumbled upon the answer to my question in this thread.

    A brown dwarf is only a brown dwarf while it is able to maintain an internal core temperature between 106 °K and 107 °K. Should the core temperature of the brown dwarf fall below 106 °K, such as after it has fused all of its deuterium/lithium, then it ceases to be a brown dwarf and becomes a giant gas planet. In which case, any object in orbit around a "dead" brown dwarf would be considered a "moon."

    Since the label of the objects in orbit around a star does not change when the star "dies" and becomes either a white dwarf, neutron star, or black hole, then the label of the objects in orbit around a brown dwarf should not change when the brown dwarf eventually "dies" and becomes a giant gas planet. Hence, the answer to my question appears to be "moon." Satellite, naturally, still works in a more generic sense.
     
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