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Featured B First Interstellar Asteroid Found

  1. Nov 30, 2017 #101
    It is estimated that the current Solar System represents 2% of the mass of the original nebular cloud. The vast majority of asteroids are travelling through free space, not in orbit around a star.
     
  2. Nov 30, 2017 #102

    mfb

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    .... and most of them will still be in the galaxy. Their dynamics will be similar to the motion of stars.

    Most of the initial mass of the gas cloud was hydrogen and helium, by the way, the fraction that stayed here doesn't tell you anything about solid objects.
     
  3. Dec 1, 2017 #103

    OmCheeto

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    Yay!
    For days I've been trying to figure out where this stick came from.
    Fortunately, my Sol to Galactic coordinate transformation skills are nil, so I didn't even start on any calculations.
    But it appears the smarties have been trying, and there seems to be a lot of head scratching going on:

    NEWS
    ASTRONOMY,PLANETARY SCIENCE
    We still don’t know where the first interstellar asteroid came from
    Clues from ‘Oumuamua’s speed and trajectory lead to answers all over the sky map
    BY LISA GROSSMAN 11:38AM, DECEMBER 1, 2017​

    So I don't feel so stupid. :biggrin:
     
  4. Dec 4, 2017 #104

    Al_

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    Not sure about the average asteroid. Maybe the definition matters here.
    But this one, well, it's long and thin, so it is not formed by accretion. Which leaves collision. Two planets, or planetoids, or moons, or such an object and a pretty large asteroid collided. Now, maybe Oort cloud or interstellar objects sometimes collide, but interstellar space is so very huge that such collisions will be very rare. Far more likely to happen in the more crowded space a round a star. Hence, a solar system.
     
  5. Dec 4, 2017 #105

    Al_

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    Chasing it down with a rocket would require huge delta vee. But .. what about a rotating space tether? If we saw another one coming in, and had time to set it up, how long & strong would a tether have to be to have a tip velocity of say, 70km/sec? Is that even possible?

    Erm, I answered my own question. Surprisingly, the max velocity does not increase with tether length. https://en.wikipedia.org/wiki/Space_tether#Practical_materials 2 or 3 km/sec is the best we can hope for.
     
    Last edited: Dec 4, 2017
  6. Dec 4, 2017 #106
    Yes, that's quite clear. But does the formation of such objects require a cloud with sufficient mass to form a star and not just planets? The paucity of small stars compared to the expected numbers (e.g. according to a Pareto distribution) suggests such a lower limit. But I didn't found corresponding sources.
     
  7. Dec 4, 2017 #107

    Al_

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    I see. Doh.
    But, thinking about it, not unrelated is the question of how did it get up to 26km/sec? Was it due to the speed of the source objects relative to us as they dive toward a star, or just relative to us as they go their own way along between the stars? I suppose a star's involvement makes it more likely, and a big star more so? Look at it another way - if a cloud of dust formed a planet or two, without a star, why would a piece come flying at us so fast, unless the original cloud was going fast. Has it already done some flybys of stars, and completely lost all relation to it's cloud?
     
  8. Dec 4, 2017 #108
    Relative to Sun. Which is moving at 20 km/s relative to local standard of rest.

    What were the relative directions? What was the speed of Oumuamua relative to local standard of rest?
     
  9. Dec 4, 2017 #109
    Speed is relative. It could ask how we got up so fast. Such a relative speed is not unusual in interstellar space.
     
  10. Dec 4, 2017 #110

    mfb

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    20 km/s is a typical relative speed of stars. 26 km/s is nothing special.
    Well, there is a reasonable accuracy for the direction it came from, but finding a specific system is much harder as there is no obvious nearby star in that direction.
     
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