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    Default Do all stars have "Oort Clouds" ??



    Our Sun's Oort Cloud seems to extend at least a light-year away from the Sun.


    QUESTION:

    Arguing from the Cosmological Principal ("what's here is there"), could other stars have colossal cometary "Oort Clouds" too ? If so, comets could, conceivably, populate an appreciable fraction of the inter-stellar space between stars -- the disk of the Milky Way Galaxy might be a "blizzard" of such icy bodies*.
    * The Outer Oort Cloud was once believed to boast about a Jupiter's mass worth of comets (~0.001 Msol). The Inner Oort Cloud is believed to boast "tens or hundreds of times as many cometary nuclei as the outer halo" (~0.1 Msol). Thus, there is an outside chance, that (inter)stellar "Cometary Clouds" could be a galaxy-wide "blizzard" of icy bodies of not-inconsequential total mass.

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    Long Period Comets (LPCs) older than Solar System ??

    From Kenneth R. Lang. The Cambridge Guide to the Solar System, pg. 365-66:

    LPCs enter the planetary realm at all possible angles, and with every inclination to the Earth's orbital plane... LPCs move in all directions. Roughly half of them move along their trajectories in the retrograde direction, opposite to the orbital motion of the planets...

    Where did the Oort Cloud comets originally come from ? They could not have formed in their current position, b/c the material at such large distances from the young Sun would have been too sparse to coalesce...

    It [Oort Cloud] is located... up to 100,000 AU from the Sun. By comparison, the distance from the Sun to the nearest star, Proxima Centauri, is 271,000 AU... At greater distances, the stars in the neighborhood of our Solar System compete for gravitational control, and each is imagined to have its own retinue of comets.


    CONCLUSION:

    • LPCs show no "gravitational correlation" to typical, Solar System-like, motions.
    • They could not have formed as from our Sun's collapsing cloud core
    • 3/4 of the distance between Sol & Proxima Centauri (200,000 out of 271,000 AU) is occupied by LPCs


    This is completely consistent, w/ LPCs be extra-Solar objects, whose ices & rocks might predate our particular planet.

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    Sure they do, that is how stars trade biologicals.

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    Most comets may be from other solar systems | COSMOS magazine

    Most comets may be from other solar systems

    Computer simulations have revealed that famous long-period comets such as Halle-bop (pictured) are likely to have originated in another solar system...

    more than 90% of comets in the Oort Cloud were captured from other stars when the Sun spread apart from its ‘birth cluster’. Levinson said it is common for stars to be born in ‘clusters’, fed by a large cloud of gas held together by its own gravity. Around each of these stars will form comets, many of which will be stripped from the star by the gravity of the cluster.

    When some of the stars grow old enough, they emit strong stellar winds that literally blow the gas from the cluster, destroying its gravitational hold on the stars. Once this occurs the cluster starts to disperse, and if a star leaves the cluster at the same velocity as a comet from another star, the comet can be captured.

    Trillions of comets on average originally form around each star, and the study’s computer simulations show up to a quarter of this average can end up in an Oort Cloud.

    The fact the Sun stole so many comets doesn’t mean other stars missed out on the chance to have an Oort Cloud of their own. “It’s not a zero sum game,” said Levison, and noted for all of the comets captured by stars when the cluster dispersed, there are many times more floating around in inter-stellar space.
    Last edited by Widdekind; 06-14-2010 at 08:00 AM.

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    Sorry for raising this thread from death, but this is a pretty interesting question in my mind. If other stars have significant Oort clouds, it would only follow that comets and the like would be traded between systems on close passes of stars, whether they remained in stable orbits or were sent into the inner solar system and destroyed.

    For instance, Alpha Centauri is currently 4.37 ly (276kAU) away from us, but in about 30,000AD it will only be 3.26 ly (206kAU) away. If our Oort cloud truly extends past 100kAU and AC has a similar or slightly larger one (the system is 2x Ms), perturbations in the orbits of both clouds would be intense. Objects in the right direction tenuously holding on to 100kAU orbits around Sol would now be just as close to a system that's twice as massive.

    At ~0.5 solar masses Gliese 710 is likely to pass within our Oort cloud in 1.4Myr, and it would be reasonable to assume that some time in the billions of years since Sol left its birth cluster it's had as close or closer encounters with even more massive systems with their own clouds. I would think at least some cometary matter in our system is extra-planetary in nature.
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    Reading this thread is conjuring images of a natural cosmic transportation system in my head. All aboard for the Sol system!

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    As long as you don't mind waiting at the station for a few thousand millenia
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    Quote Originally Posted by jenniferchristine View Post
    As long as you don't mind waiting at the station for a few thousand millenia
    Doesn't sound that much worse than what they make you go through at the airport.
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