- 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.
Is there a point where you, as a sober professional, start to entertain outlandish theories about something like this? Has this crossed that threshold?
Perhaps someone has discovered warp drives (is gravitational wave detection the first step) and the Federation have sent a ship to observe us.
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... :)
Ah, but it's a carrier for the small, stealthy probes!
That's what they want you to think!
So you're saying it's a bio-ship! ldenneau confirms it's aliens!
See some interesting back-and-forth on this here: https://www.reddit.com/r/space/comments/7ealls/solar_systems...
https://www.popsci.com/interstellar-object-solar-system#page...
That is presumably because there’re lots of these objects, but we can only detect the ones closest to us.
So maybe we can expect it to spin (and/or see it doesn't and speculate on the reasons for that)
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 :)