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I'm still convinced this is an alien probe. I mean look at that trajectory. 0.163 AU from Earth - what are the odds? The spinning is irrelevant surely - I mean,

I'm still convinced this is an alien probe. I mean look at that trajectory. 0.163 AU from Earth - what are the odds? The spinning is irrelevant surely - I mean, it's all relative, so as far as ’Oumuamua is concerned, we're spinning. Maybe it was spinning that way to stay aligned with a distant companion for communication.

szilardboy 8y ago
What’s special about 0.163 AU? Does it have a mathematical significance?
- inevitable2 8y ago
  AU stands for Astronomical unit, and it's used for measuring distances in space smaller than light-years. 1 AU is the distance between the Earth and the Sun. 0.163 AU tells you how close it came to earth.
  - rbanffy 8y ago
    I'd prefer to use light seconds/minutes for that. Not only it's easier to grasp (0.163 AU seems awfully close, but 81 light seconds sounds reassuringly far) but it'll probably be more helpful when we have to communicate across these distances.
- azernik 8y ago
  Just that it's unusually close.
  - RobertoG 8y ago
    As we are in paranoid mode (and it's fun to be, isn't it?): not only it's unusually close, but it seems that Earth is the planet it pass closer in all the Solar System. Maybe somebody should check if that "slightly acceleration" bring it closer or farther to Earth. Maybe we have been photographed. I hope it's not that somebody shoot us and failed.
    - ssijak 8y ago
      Aliens got us just before GDPR, sneaky bastards!
  - dwaltrip 8y ago
    There is a bit of sampling bias, given that we are looking for space objects from Earth, and so it easier to detect something that comes closer to Earth. Not sure how significant the bias is for an object of this size and speed, but I'm guessing that it is probably a relevant factor.
interfixus 8y ago
Two more of them, and I'd say you have an excellent case.
- lawlessone 8y ago
  They do everything in threes.
  - dboreham 8y ago
    A Arc, B Arc...
pilsetnieks 8y ago
If one were so inclined, they could argue that the spinning is in fact very relevant, as it would allow a static camera or other observation device a full 360° view along all axes.
- rbanffy 8y ago
  Any civilization capable of building an interstellar craft would certainly have mastered the ability to move a camera by then ;-)
  - pilsetnieks 8y ago
    Stealth. If you wanted to reveal yourself, you wouldn't need to disguise your probe as space debris.
gmt2027 8y ago
If you're right about the spin for alignment, we should be looking into deep space in the direction of it's axis. Presumably, this direction is erratic but there may be orientations that dominate over time. A tumbling probe that doubles as a cosmic pointer to home. Cool.
p2detar 8y ago
This has always fascinated me. We can actually build giant spaceships (space stations) inside asteroids and use them for interstellar travel. All the resources we need, including ice would be at our disposal. Like traveling with your own mini-planet. Dirk Schulze had taken that as a subject into his sci-fiction book - Alien Encounter.
- huhtenberg 8y ago
  For the book, the reviews on Goodreads aren't very good :-/ https://www.goodreads.com/book/show/18268008-alien-encounter https://www.goodreads.com/book/show/18268008-alien-encounter
  - p2detar 8y ago
    That's true, but I personally found it pretty engaging. In fact, I read the last 150+ pages in one night. I'd give it at least 4 stars.
- tomp 8y ago
  From an energy perspective, it's likely better to build your own station (from an asteroid - or alternative, remove all the mass from the asteroid that you don't need) - that way, you're only accelerating exactly the mass that you need, not wasting any energy accelerating the rest of an asteroid.
  - neuronic 8y ago
    I think he is talking about chilling on the asteroid while it follows its known trajectory undisturbed, simply because they are packed with useful resources we can gobble up while waiting. Asteroid are per definition not interstellar though (until Oumuamua?).
    - rbanffy 8y ago
      An interesting approach would be to send an automated ship builder robot fleet to dismantle an asteroid and board the fully furnished ship when it makes another close approach, and then boosting it to its final destination. I'd love to see a scenario where we'd build robot terraforming fleets that'd land on an uninhabited planet, make it habitable, complete with spaceports, cities, factories, crops (all permanently tended for robots), build a couple extra fleets and launch to their next most promising targets. And then, for some reason, humans lose interest in all that and someone else wakes up to find a universe full of 60's futuristic utopian planets nobody ever lived in.
jobigoud 8y ago
The odds we expect depend on our detection ability. Maybe there are thousands of these objects but we saw this one only because it passed so close to Earth.
- walrus01 8y ago
  There is fairly strong consensus in the astronomy community that possibly hundreds of Sednoid class objects exist, and those are in relatively normal orbits compared to things which are beyond solar escape velocity. But so far we've only found 3 or 4 Sednoids. https://en.m.wikipedia.org/wiki/Sednoid https://en.m.wikipedia.org/wiki/Sednoid
  - hannasanarion 8y ago
    Sednoids orbiting in the kuiper belt are totally different from extrasolar objects on hyperbolic trajectories. Oamuamua passed inside Mercury's orbit.
    - walrus01 8y ago
      Yes, but both classes of objects are very dificult to detect, due to distance, size and lack of brightness. We only detected the extrasolar object once it had already passed perihelion and was on its way out.
- mbel 8y ago
  "Such an intrinsically faint body could be discovered only thanks to the close Earth flyby in October 2017, which created a tremendous opportunity for the first detailed characterization of a minor object of exosolar origin." https://arxiv.org/ftp/arxiv/papers/1712/1712.00437.pdf https://arxiv.org/ftp/arxiv/papers/1712/1712.00437.pdf
w1nt3rmu4e 8y ago
I prefer a complementary theory -- that it's a spent stage of a multi-stage spacecraft. If the primary stage were decelerating for a rendezvous with Earth, then any stage that made it to full acceleration would reach us first, probably getting close and then flinging back out of the solar system, just like this did. Easy enough to test -- we'll eventually see another object following the same trajectory, give or take, but that's decelerating. (Cue the dramatic music.)
- chimprich 8y ago
  "And on far-off Earth, Dr. Carlisle Perera had as yet told no one how he had wakened from a restless sleep with the message from his subconscious still echoing in his brain: The Ramans do everything in threes."
  - turbo_fart_box 8y ago
    Great series of books! Every time I see a thread about this big rock I think of Rama.
    - interfixus 8y ago
      Beg to differ. Great book. Awful cheap hacks posing as sequels. I regret reading them - they've nearly ruined the original for me.
      - notsofastbuddy 8y ago
        The final reveal was mind-numbingly bad.
      - rbanffy 8y ago
        My personal theory is that Clarke's writing partners sedated and tied him inside a closet until the book was finished. That's the only way to explain how awful some of his last books were. Having said that, I liked Richter 10. Too bad the co-author died before they could write another one.
mattlondon 8y ago
Looking at the images on that site, the trajectory doing a "fly by" of a lot of the planets did look remarkedly like the sort of thing we've being doing for decades in our own solar system [1]- line up a bunch of planets and use gravity slingshots to do a close fly-by to get a closer look. The thought makes me have goose-bumps. Did some alient race just take a close look at us? Was there a voyager-style plaque on it? I guess we'll never know now. Occam tells us that in reality it is most likely just some space debris from some ancient rock-smashing incident, but the fact that this thing continues to defy classification allows us some space to imagine! 1 - https://duckduckgo.com/?q=voyager+gravity+slingshot+diagram&iar=images&iax=images&ia=images https://duckduckgo.com/?q=voyager+gravity+slingshot+diagram&...
- godshatter 8y ago
  I wonder if it's speed increased on it's way out. Maybe it's on a multi-system route, using gravity assist as it goes to cut the route time down by a few thousand years here or there as it circles back around to it's home system. Must be very patient aliens, assuming no FTL messaging tech.
planteen 8y ago
> 0.163 AU from Earth - what are the odds? Look at it from a sampling bias perspective. The object at its brightest was very dim (19th magnitude) and moving fast. The ability for rapid, repeating full sky surveys is recent (PanSTARRS had been online for around a decade). The limiting magnitude of PanSTARRS is 24th. So if such other such objects exist, of course we are going to find the closest ones first since they are the brightest.
deleted 8y ago
[deleted]
TangoTrotFox 8y ago
There's another little fun point here. If this was a probe, the point where you'd accelerate to have the greatest effect on your trajectory would be exactly where it did - at one of its semi-major points - where its trajectory turns.
jimijazz 8y ago
I want this to be an alien ship so badly!
tonmoy 8y ago
> The spinning is irrelevant surely - I mean it’s all relative That is incorrect. All motion is not relative, only intertial motion is relative. Spinning implies acceleration on a body which is measurably different from any reference frame compared to a body that is not accelerating
- sjclemmy 8y ago
  What I meant was, the origin of the object may have been in a different inertial frame of reference to our solar system, so the 'spin' as far as it is concerned is not spin.
  - burke 8y ago
    This is not a thing though. Spin is spin, regardless of reference.
    - sjclemmy 8y ago
      I really misunderstand my relativity then.
      - wcoenen 8y ago
        You seem to know that the rules of physics should hold in any inertial (i.e. non-accelerating) reference frame. But the thing you missed is that a spinning reference frame cannot be inertial. There is centripetal acceleration when something spins.
      - justinpombrio 8y ago
        You've got the right general idea, but the principle of relativity only applies to constant velocity motion. If two astronauts float past each other in space, either of them can claim that they're motionless and the other is moving past them. However, if one of them is accelerating or spinning, they'll both agree on who it is. https://en.wikipedia.org/wiki/Principle_of_relativity https://en.wikipedia.org/wiki/Principle_of_relativity https://en.wikipedia.org/wiki/Inertial_frame_of_reference https://en.wikipedia.org/wiki/Inertial_frame_of_reference
jakeinspace 8y ago
How could spinning rapidly possibly help for communication? Unless this distant companion is moving at many times the speed of light in a massive ellipse. Also, as someone else mentioned, rotational motion isn't intertial, it's not just relatively different from us on Earth.
tantalor 8y ago
> what are the odds? 100%, because it happened

szilardboy 8y ago

What’s special about 0.163 AU? Does it have a mathematical significance?

inevitable2 8y ago
AU stands for Astronomical unit, and it's used for measuring distances in space smaller than light-years. 1 AU is the distance between the Earth and the Sun. 0.163 AU tells you how close it came to earth.
- rbanffy 8y ago
  I'd prefer to use light seconds/minutes for that. Not only it's easier to grasp (0.163 AU seems awfully close, but 81 light seconds sounds reassuringly far) but it'll probably be more helpful when we have to communicate across these distances.
azernik 8y ago
Just that it's unusually close.
- RobertoG 8y ago
  As we are in paranoid mode (and it's fun to be, isn't it?): not only it's unusually close, but it seems that Earth is the planet it pass closer in all the Solar System. Maybe somebody should check if that "slightly acceleration" bring it closer or farther to Earth. Maybe we have been photographed. I hope it's not that somebody shoot us and failed.
  - ssijak 8y ago
    Aliens got us just before GDPR, sneaky bastards!
- dwaltrip 8y ago
  There is a bit of sampling bias, given that we are looking for space objects from Earth, and so it easier to detect something that comes closer to Earth. Not sure how significant the bias is for an object of this size and speed, but I'm guessing that it is probably a relevant factor.

interfixus 8y ago

Two more of them, and I'd say you have an excellent case.

lawlessone 8y ago
They do everything in threes.
- dboreham 8y ago
  A Arc, B Arc...

pilsetnieks 8y ago

If one were so inclined, they could argue that the spinning is in fact very relevant, as it would allow a static camera or other observation device a full 360° view along all axes.

rbanffy 8y ago
Any civilization capable of building an interstellar craft would certainly have mastered the ability to move a camera by then ;-)
- pilsetnieks 8y ago
  Stealth. If you wanted to reveal yourself, you wouldn't need to disguise your probe as space debris.

gmt2027 8y ago

If you're right about the spin for alignment, we should be looking into deep space in the direction of it's axis. Presumably, this direction is erratic but there may be orientations that dominate over time. A tumbling probe that doubles as a cosmic pointer to home. Cool.

p2detar 8y ago

This has always fascinated me. We can actually build giant spaceships (space stations) inside asteroids and use them for interstellar travel. All the resources we need, including ice would be at our disposal. Like traveling with your own mini-planet. Dirk Schulze had taken that as a subject into his sci-fiction book - Alien Encounter.

huhtenberg 8y ago
For the book, the reviews on Goodreads aren't very good :-/ https://www.goodreads.com/book/show/18268008-alien-encounter https://www.goodreads.com/book/show/18268008-alien-encounter
- p2detar 8y ago
  That's true, but I personally found it pretty engaging. In fact, I read the last 150+ pages in one night. I'd give it at least 4 stars.
tomp 8y ago
From an energy perspective, it's likely better to build your own station (from an asteroid - or alternative, remove all the mass from the asteroid that you don't need) - that way, you're only accelerating exactly the mass that you need, not wasting any energy accelerating the rest of an asteroid.
- neuronic 8y ago
  I think he is talking about chilling on the asteroid while it follows its known trajectory undisturbed, simply because they are packed with useful resources we can gobble up while waiting. Asteroid are per definition not interstellar though (until Oumuamua?).
  - rbanffy 8y ago
    An interesting approach would be to send an automated ship builder robot fleet to dismantle an asteroid and board the fully furnished ship when it makes another close approach, and then boosting it to its final destination. I'd love to see a scenario where we'd build robot terraforming fleets that'd land on an uninhabited planet, make it habitable, complete with spaceports, cities, factories, crops (all permanently tended for robots), build a couple extra fleets and launch to their next most promising targets. And then, for some reason, humans lose interest in all that and someone else wakes up to find a universe full of 60's futuristic utopian planets nobody ever lived in.

jobigoud 8y ago

The odds we expect depend on our detection ability. Maybe there are thousands of these objects but we saw this one only because it passed so close to Earth.

walrus01 8y ago
There is fairly strong consensus in the astronomy community that possibly hundreds of Sednoid class objects exist, and those are in relatively normal orbits compared to things which are beyond solar escape velocity. But so far we've only found 3 or 4 Sednoids. https://en.m.wikipedia.org/wiki/Sednoid https://en.m.wikipedia.org/wiki/Sednoid
- hannasanarion 8y ago
  Sednoids orbiting in the kuiper belt are totally different from extrasolar objects on hyperbolic trajectories. Oamuamua passed inside Mercury's orbit.
  - walrus01 8y ago
    Yes, but both classes of objects are very dificult to detect, due to distance, size and lack of brightness. We only detected the extrasolar object once it had already passed perihelion and was on its way out.
mbel 8y ago
"Such an intrinsically faint body could be discovered only thanks to the close Earth flyby in October 2017, which created a tremendous opportunity for the first detailed characterization of a minor object of exosolar origin." https://arxiv.org/ftp/arxiv/papers/1712/1712.00437.pdf https://arxiv.org/ftp/arxiv/papers/1712/1712.00437.pdf

w1nt3rmu4e 8y ago

I prefer a complementary theory -- that it's a spent stage of a multi-stage spacecraft. If the primary stage were decelerating for a rendezvous with Earth, then any stage that made it to full acceleration would reach us first, probably getting close and then flinging back out of the solar system, just like this did. Easy enough to test -- we'll eventually see another object following the same trajectory, give or take, but that's decelerating. (Cue the dramatic music.)

chimprich 8y ago
"And on far-off Earth, Dr. Carlisle Perera had as yet told no one how he had wakened from a restless sleep with the message from his subconscious still echoing in his brain: The Ramans do everything in threes."
- turbo_fart_box 8y ago
  Great series of books! Every time I see a thread about this big rock I think of Rama.
  - interfixus 8y ago
    Beg to differ. Great book. Awful cheap hacks posing as sequels. I regret reading them - they've nearly ruined the original for me.
    - notsofastbuddy 8y ago
      The final reveal was mind-numbingly bad.
    - rbanffy 8y ago
      My personal theory is that Clarke's writing partners sedated and tied him inside a closet until the book was finished. That's the only way to explain how awful some of his last books were. Having said that, I liked Richter 10. Too bad the co-author died before they could write another one.

mattlondon 8y ago

Looking at the images on that site, the trajectory doing a "fly by" of a lot of the planets did look remarkedly like the sort of thing we've being doing for decades in our own solar system [1]- line up a bunch of planets and use gravity slingshots to do a close fly-by to get a closer look. The thought makes me have goose-bumps. Did some alient race just take a close look at us? Was there a voyager-style plaque on it? I guess we'll never know now. Occam tells us that in reality it is most likely just some space debris from some ancient rock-smashing incident, but the fact that this thing continues to defy classification allows us some space to imagine! 1 - https://duckduckgo.com/?q=voyager+gravity+slingshot+diagram&iar=images&iax=images&ia=images https://duckduckgo.com/?q=voyager+gravity+slingshot+diagram&...

godshatter 8y ago
I wonder if it's speed increased on it's way out. Maybe it's on a multi-system route, using gravity assist as it goes to cut the route time down by a few thousand years here or there as it circles back around to it's home system. Must be very patient aliens, assuming no FTL messaging tech.

planteen 8y ago

> 0.163 AU from Earth - what are the odds? Look at it from a sampling bias perspective. The object at its brightest was very dim (19th magnitude) and moving fast. The ability for rapid, repeating full sky surveys is recent (PanSTARRS had been online for around a decade). The limiting magnitude of PanSTARRS is 24th. So if such other such objects exist, of course we are going to find the closest ones first since they are the brightest.

deleted 8y ago

[deleted]

TangoTrotFox 8y ago

There's another little fun point here. If this was a probe, the point where you'd accelerate to have the greatest effect on your trajectory would be exactly where it did - at one of its semi-major points - where its trajectory turns.

jimijazz 8y ago

I want this to be an alien ship so badly!

tonmoy 8y ago

> The spinning is irrelevant surely - I mean it’s all relative That is incorrect. All motion is not relative, only intertial motion is relative. Spinning implies acceleration on a body which is measurably different from any reference frame compared to a body that is not accelerating

sjclemmy 8y ago
What I meant was, the origin of the object may have been in a different inertial frame of reference to our solar system, so the 'spin' as far as it is concerned is not spin.
- burke 8y ago
  This is not a thing though. Spin is spin, regardless of reference.
  - sjclemmy 8y ago
    I really misunderstand my relativity then.
    - wcoenen 8y ago
      You seem to know that the rules of physics should hold in any inertial (i.e. non-accelerating) reference frame. But the thing you missed is that a spinning reference frame cannot be inertial. There is centripetal acceleration when something spins.
    - justinpombrio 8y ago
      You've got the right general idea, but the principle of relativity only applies to constant velocity motion. If two astronauts float past each other in space, either of them can claim that they're motionless and the other is moving past them. However, if one of them is accelerating or spinning, they'll both agree on who it is. https://en.wikipedia.org/wiki/Principle_of_relativity https://en.wikipedia.org/wiki/Principle_of_relativity https://en.wikipedia.org/wiki/Inertial_frame_of_reference https://en.wikipedia.org/wiki/Inertial_frame_of_reference

jakeinspace 8y ago

How could spinning rapidly possibly help for communication? Unless this distant companion is moving at many times the speed of light in a massive ellipse. Also, as someone else mentioned, rotational motion isn't intertial, it's not just relatively different from us on Earth.

tantalor 8y ago

> what are the odds? 100%, because it happened