Is 1I/’Oumuamua an Alien Spacecraft?

No, I don’t think there’s any reason to think it is, but there’s lots of chatter on Twitter that suggest astronomers think it could be:

So what’s going on?

For the first time, astronomers think they have found an interstellar asteroid.  It is clearly on an escape trajectory, and everything about its path is consistent with a free-floating asteroid that was ejected from another star system and is now happening to buzz by the Sun:

There are several things that have astronomers talking “spaceship”:

  • Its discovery closely tracks the opening chapter of the book Rendezvous with Rama, by Arthur C. Clarke, about the discovery of an interstellar spaceship on a similar trajectory to ‘Oumuamua.
  • We were expecting the first discovered interstellar rocks (we know they must be out there) to be comets, since our own Solar System’s Oort cloud (populated by nearly-ejected Solar System detritus) is mostly comets. The fact that it is not a comet has people scratching their heads.
  • One of the recent measurements of its shape finds it to have a 10:1 axis ratio: this is not typical of asteroids, but is not uncommon for ships in science fiction (the 2001 monolith was 1:4:9)
  • One of the recent measurements of its color has it very red, similar to metallic asteroids

In many ways, this discovery tracks the excitement around Tabby’s Star: a prediction of how we might discover alien life was made (Clarke for ‘Oumuamua, Luc Arnold for Tabby’s Star); and later an anomalous object was found roughly tracking that prediction but confounding natural explanation.

I’m glad that astronomers are talking about this in a SETI context (and this is SETI), but my personal prior on this is that there is not much reason to get excited about the SETI angle.

That’s because there are several important differences between ‘Oumuamua and Tabby’s Star:

  • The data on Tabby’s Star from Kepler are exquisite.  What’s more, only after being convinced that there was no chance of instrumental error did it really get interesting.  The data on ‘Oumuamua is thin: different groups are getting different sizes, rotation periods, axial ratios, and colors for the object, meaning that it hasn’t been well measured yet.  For instance:

  • The various values people get for the axial ratio vary from the hard-to-understand 10:1 to the more ordinary 3:1.  In other words, it’s not at all clear that this characteristic of ‘Oumuamua is actually all that anomalous—the 10:1 measurement could be in error.
  • Tabby and her team put 2 years of hard work into understanding that star.  Only after all of that work was the “hypothesis of last resort” something worth publishing. ‘Oumuamua was discovered a month ago.
  • Tabby’s team’s ruling out of most natural explanations built on decades of stellar astrophysics and understanding of stars and their environments.  ‘Oumuamua is the first interstellar asteroid we’ve seen, so we have very little to go on.

So I’ll need to see a lot more data and hard, critical analysis of the anomalies in ‘Oumuamua before I get interested in the SETI angle at the level I am for Tabby’s Star.

That said, I’m glad that astronomers are, on the informal forum of Twitter anyway, having a SETI discussion about the prospect of discovering interstellar probes passing through the Solar System.  It’s a neat topic, and once worth thinking about.  I hope ‘Oumuamua inspires more real work on it in the peer-reviewed literature, including concrete suggestions of what to look for when future interstellar objects are discovered passing through.

[Update: please see this Twitter thread by Michele Bannister:

This article (in German, but Google Translate) by Daniel Fischer:

Interstellarer Gast ʻOumuamua erstaunlich länglich

and the comment by Darin Ragazzine below for more-informed takes on this whole issue. Where they contradict me, you should trust them, because they are actual planetary scientists that work in this field.

12 thoughts on “Is 1I/’Oumuamua an Alien Spacecraft?

  1. Paul Brennick

    I tend to agree with you, Old Dude. The government has a poor track record about this; I recall the ufo stories where I don’t believe we ever got a satisfactory explanation.

  2. jtw13 Post author

    Unfortunately, since we don’t know the size of the asteroid, we don’t know what infrared emission to expect. In fact, planetary scientists often work the other way: by comparing the infrared to optical brightness of an asteroid, they infer its size and reflectivity (albedo).

  3. David

    I know its unlikely, but has anyone looked to see if there was a big IR excess flux over what one would expect if the object was a simple black body ? True its tumbling and elongated so the changing geometry will change the emitted flux so one would have to take that into account.

  4. Harry R Ray

    Jason: Will the fact that Oumuamua appears to be tumbling mean that there could be MINOR corrections to its currently projected periastron passage(currently at 0.255 AU) and its closest approach to Earth(currently at 0.1616AU. ALSO: Just an idea; have some of your graduate students compute Oumuamua,s projected closest approach to ALL OF THE OTHER PLANETS!

  5. George Curran

    No reason not to bombard the object with communications on every known frequency while it is fairly close to us. Given the energy curve needed to exit the solar system they could not reasonably be expected to slow down, but a response is not beyond the realm of possibility. If it were unmanned or the crew in stasis, at least our message would probably be recorded.

  6. Dryson

    Rethinking the Dyson Swarm

    Standby Starfleet….we are picking something up the from glyph….its a small packet a few terrabytes in size…its transmitting from a small egg shaped capsule

    Understood…beam it directly to cargo bay 214.

    Beaming now…..

    Vantablack, the closest color that has been created that does not allow light to escape.

    “Vantablack is composed of a forest of vertical tubes which are “grown” on a substrate using a modified chemical vapor deposition process (CVD). When light strikes Vantablack, instead of bouncing off, it becomes trapped and is continually deflected among the tubes, eventually becoming absorbed and dissipating into heat.”

    Most of the time we think of large solar arrays collecting photons and then converting them into heat. But what if a SETI (Sentient Extra Terrestrial Intelligence) just a few hundred years more advanced than humans had incorporated a material similar to Vantablack into its energy harvesting and production systems?

    A collector would function basically the same as a Thermoelectric Generator. The only difference is that a layer of Vantablack material would line the outside shell of the collector on all of its faces to collect as much light as possible from all directions.

    The light is the bounced around inside of the vertically aligned carbon nano tube arrays where the light continually deflected among the tubs becomes absorbed and dissipates as heat.

    The heat is then transferred to a heat application layer where it is then converted into electrical power.

    This type of electrical generator would see a 100% power output with only a very small fraction of heat waste as most of the heat would be used to generate electricity.

    I don’t know if this possible or not but is there a method to determine how much light or heat is present within the centers of each dip that takes place while the transit occurs?

    Such an array would create a lot of confusion like it has for Earth due to the reduced presence of Flux. But with a Vantablack material covering a TEG we can purposely assume that the reason why the Flux seems odd is because all of diminishing luminosity present because of the a Vantablack type material absorbing all photons that come into contact with the Vantablack material.

    A Vantablack Swarm would seem even more feasible than a Dyson Swarm and even more efficient at collecting solar energy than a TEG Array around a Super Gas Giant would because the material would collect all light passing through the area the Vantablack Array was located at.

    With this type of technology a star ship would never be without electrical power ever again. A star ship could reduce its mass by nearly 20% by replacing batteries that generate electricity to capacitors that store and transfer electricity.

    Einstein said that it would take an infinite source of power to operate a starship….how much more power do you need if it not be all of the light of the heavens.

    They called it Hope in the Darkness and all that does not glitter is gold.

  7. Phil Stooke

    Of course they would tell us! Who would keep the most exciting discovery of the century under wraps? Nooooo-body!

  8. Patrick

    In addition to observing the object itself, it might be a good idea to look back through observations in the vicinity of the arrival path over the previous weeks, months or even years prior to detection. Look for anything unusual such as a rise in x-rays or other high energy particles, an optical flare, a highly blue-shifted object, on the low-probability idea that 1I might have slowed itself from a much higher velocity. I mean, as long as we’re entertaining the ETI possibility.

  9. Darin Ragozzine

    I have some expertise in this area so thought I would comment while the turkey is in the oven. I’m not on Twitter and this discussion is evolving rapidly, but I’d like to contribute some thoughts that support Jason’s main thesis of “not a spaceship” and “we don’t know as much as we need to.”

    You mention that the color is similar to metallic asteroids, which isn’t untrue, but it could be misleading. We have no evidence that it is made out of metal and there are many objects with similar colors/spectra that are not made out of metal. The color, spectrum, and lack of detectable coma (a comet’s outgassing atmosphere) are all consistent with either a rocky object or an extinct comet. As has been pointed out on Twitter and as my student discusses in our paper on interstellar objects (Cook et al. 2016, asteroids can indeed be ejected into interstellar space in the planet formation process. Furthermore, we point out in our paper that you might expect to detect asteroids first, especially at Oumuamua’s size, because most comets tend to break up at a size of ~1 km, while asteroids can have any size. This means that you can have huge numbers of sub-km bodies compared to every comet and therefore the typical asteroid gets closer and can be as bright as an outgassing comet to our telescopes (Section 4.4 of Cook et al. 2016). I conclude that the color and spectrum are not highly unusual enough that our sample of 1 object implies an exotic explanation.

    The incredible lightcurve variations (it changes in brightness by a factor of ~10) are definitely unusual (read: very rare in the solar system) and require an explanation. Some comments on this:
    – There is a lot of uncertainty and disagreement on the axial ratio required.
    – Inferring an axial ratio requires assuming a location (or range of locations) for the orbital pole… however this means that the axial ratios reported are generally underestimated. With the right pole location, the true axial ratio could be 100:1!
    – Another key issue is that to go from a lightcurve to a shape you must ASSUME properties for the albedo of the object. For example, I could take a *sphere* and paint it just right to produce Oumuamua’s extreme lightcurve. This is, again, where our solar system intuition kicks in (and, as Jason points out, this is where problems in interpretation arise). In the solar system, most lightcurve variations are caused by shape and not albedo. When they are caused by albedo, this usually includes variations in color and shape (as in the most unusually shaped large object in the solar system, my favorite, the dwarf planet Haumea). Oumuamua’s lightcurve, at the present time, seems to show a pretty similar color over the entire surface (Meech et al. 2017), which, in the solar system, would be commonly interpreted as implying that the brightness variations are due to shape.

    All these taken together, I think the least exotic solution (i.e., certainly one that would need to be ruled out before any serious consideration of intelligence) is that the lightcurve is caused by a combination of both shape and albedo variegations. The dark and bright sides of Iapetus, which differ in albedo by a factor of 10, have pretty similar spectra/colors. It is plausible to have a surface with dark red and light red sides sufficiently different to produce the extreme brightness variations, especially if you allow for some shape effects as well.

    I’ll note that continued observations and merging the rapidly evolving results will likely help in testing this hypothesis. The best would be to get observations from different viewing positions since that can review a lot about the shape. Unfortunately the viewing angle only changes by several degrees, but if the axial ratio is so extreme, this should be detectable. I think we’ll be able to say much more about the shape/color/albedo issue in a few months, so patience (as with Tabby’s star) is definitely an important part of drawing extreme conclusions.

    Finally, I’ll disagree with Jason that we know too little to compensate for survivor bias. The mechanisms for ejecting material into interstellar space are entirely gravitational. Jupiter is so massive, it doesn’t care what size of asteroid/comet it is flinging out and it certainly does not care about the shape. It is the case that objects in the solar system of Oumuamua’s size are different in that they undergo significant collisional processing where Oumumua’s collisional processing stopped once it was ejected from its natal system. The collisional processing in early stages of planet formation (that Oumuamua would have participated in) seem unlikely to be that different, so I’d be surprised if you could explain the weird shape that way. There are no processes in interstellar space that would change the shape of an object.

    If the issue is actually albedo variegation, as I hypothesis might be important, then the understanding is on much shakier ground. There are lots of things we don’t understand about colors and albedos of small bodies in our own solar system where we have much more knowledge. I don’t know if our knowledge is significantly worse in the unbound-to-a-star regime, but that doesn’t help. Although I am biased as a dynamicist, I think having weird albedo variations is more unusual-but-not-out-of-the-realm-of-explanability than having an axial ratio of 10:1.

    This comment ended up being longer than I expected, but hopefully useful in exploring this question. Please pass it around the twitterverse if you find it interesting. :)

    Darin Ragozzine
    Brigham Young University

  10. Old dude

    Do you actually think that they would tell us, if they knew that it was a spaceship?
    Myself I don’t think so – Better to keep the lie that We are the intelligent life form !

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