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I recommend anyone interested read the paper which is available as a preprint from Nature (for the moment): goo.gl/cSsHoj (link shortened due to having an embed

I recommend anyone interested read the paper which is available as a preprint from Nature (for the moment): goo.gl/cSsHoj (link shortened due to having an embedded access token). Some tantalizing points from the paper: - They constrained the aspect ratio in two dimensions to be 10:1:C, but the third dimension is unconstrained. Depending on which axis the object is rotating around, C could either be 1, or 20. Either of these would be an essentially unique object within the solar system. This is a really weird shape. - If the object is rotating around its short axis, it must have internal tensile strength (ie, it's a solid object, not just a pile of dust/gravel accreted by gravity). Lower bound on the required tensile strength is 3 Pascal (very little). - There is essentially no dust/ice on the object - less than 1 kg within 2.5". So it's not a comet, and would have to be asteroidal. This conflicts with our current understanding of what objects would be in interstellar space. Current models have almost all objects ejected from our system being icy comets. This object would be analogous to a Manx comet, ie a rocky asteroid in a highly elliptical long period orbit. - The shape of the observed light curve deviates from the best-fit triaxial ellipsoid in a way that suggests large flat or concave sections. It would take unrealistically large albedo variations to produce the same deviation without flat/concave sections. And of course, of all the planets in the solar system, it made its closest approach to Earth, an astronomical "near miss" at just 0.16 AU :)

robin_reala 9y ago
And of course, of all the planets in the solar system, it made its closest approach to Earth, an astronomical "near miss" at just 0.16 AU That is presumably because there’re lots of these objects, but we can only detect the ones closest to us.
- Tossrock 9y ago
  The authors estimate that there is ~1 such object within 1 AU of the sun at any given time. So, more common than we previously expected, but not exactly teeming. You're right that it was detected due to its nearness though - it was picked up in a routine near-Earth object survey by Pan-STARRS
  - ldenneau 9y ago
    If there is one within 1 AU of the Sun at any given time, then there are ~10^16 of them within a sphere out to the nearest star. I'll leave it to you to decide whether that's teeming or not.
    - Tossrock 9y ago
      Dr. Denneau, what an honor that you dropped by this comment thread! Congratulations on the publication, it's a truly groundbreaking discovery :) 10^16 is pretty mindbogglingly huge, but then again so is 4 light years...
    - soVeryTired 9y ago
      Surely they're more dense near the sun? Not sure you can assume a uniform spacing and not account for the gravitational attraction. But I'm sure you know more about this than I do.
      - jerf 9y ago
        If they're not being captured, they're just being perturbed by the sun a bit, not collected.
  - bmm6o 9y ago
    1 within 1 AU of the sun means that there should be one passing within 0.16 AU of us on a ~yearly basis.
tehwalrus 9y ago
- strange aspect ratio - tensile strength (it should be cartwheeling, there is a physics theorem which means everything tends to this configuration) - large flat or concave sections. - others are reporting it's mostly metallic. I'll say it: did anyone consider an alien spaceship? The paper seems to deduce "asteroidal" by ruling out other things, rather than by a positive measurement of rock spectra, unless I've misread it.
- ldenneau 9y ago
  Co-author here. We obtained spectroscopic measurements of 'Oumuamua, and its surface closely matches D-type asteroids and comet nuclei, which are dark, reddish and organic-rich.
  - tehwalrus 9y ago
    Thanks!
  - lawlessone 9y ago
    >organic-rich. So you're saying it's a bio-ship! ldenneau confirms it's aliens!
  - pbhjpbhj 9y ago
    Of course an asteroid, hollowed out somewhat, makes for a good spaceship. Especially if you're trying to be covert. Perhaps someone has discovered warp drives (is gravitational wave detection the first step) and the Federation have sent a ship to observe us.
    - wallace_f 9y ago
      If you wanted to disguise a probe, it seems the ideal form would be a black body, not to disguise it as an asteroid, I would guess. Unless they're playing mind games. Anyways, given all the EM radiation we're tossing out into the void, some species' probe out there is going to pick up our existence sooner or later. And at ~395 earth-moon distances it's difficult to imagine how effective a 400-meter object, disguised as an asteroid, would be at seeing much detail on earth. But it is tantalizing and fun to imagine--the appearance of a gravity boost... Flat surfaces... Near to earth... Lack of any ice or outgasing, a solid object, many characteristics not seen in other known-asteroids, rotating on its long axis... :)
raverbashing 9y ago
An object that has 3 different dimensions suffers from Polhode motion https://en.wikipedia.org/wiki/Polhode https://en.wikipedia.org/wiki/Polhode So maybe we can expect it to spin (and/or see it doesn't and speculate on the reasons for that)
- wallace_f 9y ago
  To quench curiosity, I wonder if someone with more knowledge here could give the probability that this object is be spinning, stable, about its axis with smaller moment of inertia?
smilbandit 9y ago
I thought the shape was a bit weird also. Most objects that we see are more like a rock but this is like a rod.

robin_reala 9y ago

And of course, of all the planets in the solar system, it made its closest approach to Earth, an astronomical "near miss" at just 0.16 AU That is presumably because there’re lots of these objects, but we can only detect the ones closest to us.

Tossrock 9y ago
The authors estimate that there is ~1 such object within 1 AU of the sun at any given time. So, more common than we previously expected, but not exactly teeming. You're right that it was detected due to its nearness though - it was picked up in a routine near-Earth object survey by Pan-STARRS
- ldenneau 9y ago
  If there is one within 1 AU of the Sun at any given time, then there are ~10^16 of them within a sphere out to the nearest star. I'll leave it to you to decide whether that's teeming or not.
  - Tossrock 9y ago
    Dr. Denneau, what an honor that you dropped by this comment thread! Congratulations on the publication, it's a truly groundbreaking discovery :) 10^16 is pretty mindbogglingly huge, but then again so is 4 light years...
  - soVeryTired 9y ago
    Surely they're more dense near the sun? Not sure you can assume a uniform spacing and not account for the gravitational attraction. But I'm sure you know more about this than I do.
    - jerf 9y ago
      If they're not being captured, they're just being perturbed by the sun a bit, not collected.
- bmm6o 9y ago
  1 within 1 AU of the sun means that there should be one passing within 0.16 AU of us on a ~yearly basis.

tehwalrus 9y ago

- strange aspect ratio - tensile strength (it should be cartwheeling, there is a physics theorem which means everything tends to this configuration) - large flat or concave sections. - others are reporting it's mostly metallic. I'll say it: did anyone consider an alien spaceship? The paper seems to deduce "asteroidal" by ruling out other things, rather than by a positive measurement of rock spectra, unless I've misread it.

ldenneau 9y ago
Co-author here. We obtained spectroscopic measurements of 'Oumuamua, and its surface closely matches D-type asteroids and comet nuclei, which are dark, reddish and organic-rich.
- tehwalrus 9y ago
  Thanks!
- lawlessone 9y ago
  >organic-rich. So you're saying it's a bio-ship! ldenneau confirms it's aliens!
- pbhjpbhj 9y ago
  Of course an asteroid, hollowed out somewhat, makes for a good spaceship. Especially if you're trying to be covert. Perhaps someone has discovered warp drives (is gravitational wave detection the first step) and the Federation have sent a ship to observe us.
  - wallace_f 9y ago
    If you wanted to disguise a probe, it seems the ideal form would be a black body, not to disguise it as an asteroid, I would guess. Unless they're playing mind games. Anyways, given all the EM radiation we're tossing out into the void, some species' probe out there is going to pick up our existence sooner or later. And at ~395 earth-moon distances it's difficult to imagine how effective a 400-meter object, disguised as an asteroid, would be at seeing much detail on earth. But it is tantalizing and fun to imagine--the appearance of a gravity boost... Flat surfaces... Near to earth... Lack of any ice or outgasing, a solid object, many characteristics not seen in other known-asteroids, rotating on its long axis... :)

raverbashing 9y ago

An object that has 3 different dimensions suffers from Polhode motion https://en.wikipedia.org/wiki/Polhode https://en.wikipedia.org/wiki/Polhode So maybe we can expect it to spin (and/or see it doesn't and speculate on the reasons for that)

wallace_f 9y ago
To quench curiosity, I wonder if someone with more knowledge here could give the probability that this object is be spinning, stable, about its axis with smaller moment of inertia?

smilbandit 9y ago

I thought the shape was a bit weird also. Most objects that we see are more like a rock but this is like a rod.