1 I/2017 UI Oumuamua

Discussion in 'Astronomy, Exobiology, & Cosmology' started by nebel, Nov 26, 2017.

  1. nebel Registered Senior Member

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    thoughts: an elongated massive body spinning fast, possibly with high iron content ,--fits what requirements? : interstellar travel. spin: artificial gravity at the extremities, iron? magnetic shielding. alternative theory: , it was launched with enough energy to reach us, good aim, near 1AU. but is waiting for us to snag it next time around, because it does not have the retrorocket, decellerating capacity. prototype for us to use on the return trip. move to alternate or humour.
     
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  3. DaveC426913 Valued Senior Member

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    This matches the description of a large number of very common natural objects.

    But sure - we hear hoof beats, let's go looking for zebras.
     
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  5. Janus58 Valued Senior Member

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    Spin rate, 1 rotation per 7.3 hrs. Not what I would call spinning fast. With an estimated length of 400 meters, tumbling end to end would produce an artificial gravity effect of 0.00000117g at the extremities.
     
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  7. nebel Registered Senior Member

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    thanks for the details I was not aware of. What are any such elongated asteroids? catch them hollow, tunnel them out, spin them up for space stations! or hitch a ride on it the next pass back to where it came from.
     
    Last edited: Nov 26, 2017
  8. DaveC426913 Valued Senior Member

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    Heh. If you ask Larry Niven, you don't need to start with elongated ones.
    He's got a great way of turning any asteroid into a large, hollow, livable space with just a solar mirror and a lot of water.

    But ... this thread is not about making space stations; it's about 'Oumuama.
     
  9. Walter L. Wagner Cosmic Truth Seeker Valued Senior Member

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  10. James R Just this guy, you know? Staff Member

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    The tendency at the extremities would be to be flung off it, not to be attracted more. Centrifugal force.

    There is no next time around. It's not in orbit around the sun.
     
  11. DaveC426913 Valued Senior Member

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    I just assumed he was conjecturing a hollow body.

    (i.e 'we hear hoof beats, let's look for unicorns').

    I assumed he meant: the next one.
     
  12. nebel Registered Senior Member

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    Caves at the ends would give you some shelter, perhaps with inside water jackets, a solid iron-rich body would withstand faster rotation, and be a ready made magnet to provide radiation shielding. Snagging the next one, and being prepared would allow to leave the solar system with already build in velocity of a massive body. far fetched? yes, but it came from far away. Potential hitchhikers in a galaxy. an almost ready made ride, thumbs up. If we could do it, they could have.too
    The interior could be stuffed with life forms or their seeds, that have proven to be viably dormant in space together with info that betters the packages on the 2 voyageurs.
    Would not theoretically a close path to a gravity well modify the trajectory to result in an eventual return?
     
    Last edited: Nov 28, 2017
  13. nebel Registered Senior Member

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    Astronomers now have started to "listen" to it, for any signs of unusual asteroid behaviour.
     
  14. DaveC426913 Valued Senior Member

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    :Frantically Photoshops a pic of a spacesuited Horton, gripping a very, long thin speck on a cosmic clover, shouting 'we are here We Are Here WE ARE HERE!':
     
  15. RADII Registered Senior Member

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    That would depend, right? If it is tumbling end-over-end, I think you could conceivably stand on the end, with your feet/boots opposing the direction of spin, & get a modicum of pressure on the soles of your boots, that might approximate a bit of gravity. It would be a fine balance, though. Lean too far 'outboard' & you get an unintended long trip of your own.
     
  16. DaveC426913 Valued Senior Member

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    No. The force you would feel would be parallel to the long axis, not perpendicular to it. i.e. you will be clinging to the side of a vertical surface.
     
  17. RADII Registered Senior Member

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    Imagine a spinning propeller, with you standing on the windward side. The known rotational period should not result in a significant centripetal force, letting the acceleration come mainly from contact with the surface itself ( lift if you will). At least that's what I'm thinking. It would not be great in any event.
     
  18. nebel Registered Senior Member

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    If it is to make the "alien cosmonauts" comfortable, they must be really fragile, but : that spin rate is within ~25 % of~ 90% of the spinning mass in our planetary system. movement shared. waltzing to the same rhythm.
     
    Last edited: Dec 14, 2017 at 8:22 PM
  19. DaveC426913 Valued Senior Member

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    I know what' you're imagining. It doesn't work that way.

    Look at the direction of Fcenterifugal in the left illo:

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    That is the force you experience while on the asteroid - the force appears to emanate from the centre of rotation, directly outward long a radius.
     
    Last edited: Dec 15, 2017 at 12:12 AM
  20. RADII Registered Senior Member

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    We'll have to agree to disagree, then.
     
  21. DaveC426913 Valued Senior Member

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    It's not a vote.

    It's science.

    Centrifugal force (what you experience on the asteroid) is aligned with the centre of rotation - i.e. parallel to the long axis.

    I'm trying to think of some simple experiments you do could to prove it to yourself. A phonograph record, a bicycle tire, a board tied to a string, spun around you. Yes, even a propellor. Anything you place on the propellor will get flung off the end of the propellor.
     
  22. RADII Registered Senior Member

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    I'm not interested in an argument. Find another participant.
     
  23. nebel Registered Senior Member

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    And countered by the strength of the material. There are many proposals to create artificial gravity via rotation of spacecraft, a good one: a massive service module , lead shielded reactor even, having a tethered living module rotating a long way off, (minimal coriolis effects). The outward force you describe, would be experienced by any object inside, part of that tumbling cucumber* and be experienced as pressure against the inside periphery, or tension in the tether of that spacecraft.
    *tumbling coincidentally at nearly the same rate as most of our system's planetary mass.
     
    Last edited: Dec 15, 2017 at 1:58 AM

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