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Oort cloud

  1. Apr 24, 2004 #1

    wolram

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    can anyone tell me if the existence of the Oort Cloud
    has been confirmed, or is it still hypothetical?
     
  2. jcsd
  3. Apr 24, 2004 #2
    No all the evidence is very tenuous. There are very many reasons to think it exists, but directly observing it is all but impossible.
     
  4. Apr 24, 2004 #3

    wolram

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    No all the evidence is very tenuous. There are very many reasons to think it exists, but directly observing it is all but impossible.
    ------------------------------------------------------------------------
    if the oort cloud does not exist is their some other
    possibility for the origins of comets?
     
  5. Apr 24, 2004 #4
    This may be of interest. http://www.solarviews.com/eng/oort.htm
     
  6. Apr 25, 2004 #5
    It seems that Sedna (2003VB12) is the very first object found belonging to the Oort cloud - except for long period comets, of course. Its distance from the Sun ranges from 76 to 900 AU (astronomical units).
     
  7. Apr 25, 2004 #6

    Nereid

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    It depends ...

    ... on what you accept as 'confirmation'! Some possible answers:

    "confirmation = direct observation of 6 trillion Oort cloud proto-comets" No.

    "confirmation = direct observation of at least one Oort cloud proto-comet" No; Sedna's orbit doesn't resemble an Oort cloud object

    "confirmation = direct observation of some objects which might have come from the Oort cloud" Yes; the Oort cloud is where the long period comets are thought to have originated; Sedna may have originated there too.

    "confirmation = observation of something which may resemble the Oort cloud around other stars" Yes; not only have several proto-planetary disks been detected (and some properties determined) around some young stars, but there are observations which suggest an 'evaporating Oort cloud', around a nova or two (IIRC)

    I don't know if observations of supernova remnants suggest that some of the material in the shells is vapourised Oort cloud comets; the 1987 SN in the LMC may provide some clues in the coming years.

    Why is it so hard to detect the Oort cloud directly? Because the objects thought to comprise it are cold (so don't radiate anything that we could detect), small and distant (so are way below the limit of detectability; if there were an Oort cloud object in the field of the recent Hubble UDF, it wouldn't be detected, unless it were really, realy big).

    Other than having the Sun go nova (and destroying all life on Earth) - so we could see the reflected light from Oort objects - there would seem to few techniques for direct observation. Maybe a variation of TAOS?
     
  8. Apr 25, 2004 #7
    I'm confused, the article by Imparcticle says that the Oort cloud has a width of 3 light years, but wikipedia
    http://en.wikipedia.org/wiki/Oort_cloud
    says that ranges from 50000 to 100000 AU, that is, from 0.79 to 1.58 ly, a width of 0.79 ly
    :confused:
     
  9. Apr 26, 2004 #8

    Nereid

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    Probably worth reading some papers on this, if you're interested. Since it's theoretical, the reasoning for the Oort cloud's size - mass, distance from the Sun, distribution of objects in it (e.g. spherical, with a concentration in the ecliptic?), thickness, ... - is perhaps the most important aspect.

    For those interested,
    there's a regular newsletter on EKOs (Edgeworth-Kuiper Objects), which sometimes has references to new papers on the Oort cloud. Jewitt's Kuiper Belt webpage has an interesting set of material, including the fact that Sedna isn't unique (2000 CR105 has a somewhat similar orbit; it's considerably smaller though), and a clear statement about Sedna not being a classical Oort cloud object.
     
  10. Apr 26, 2004 #9

    wolram

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    thanks NEREID
     
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