≡ Menu

Spitzer Size Constraints on ‘Oumuamua

The first interstellar object detected in our own Solar System, ‘Oumuamua has a pleasing name, translating from the Hawaiian as something like ‘far visitor first to arrive,’ or words to that effect. It’s also proven a frustrating catch ever since detected by the University of Hawaii’s Pan-STARRS 1 telescope on Haleakala, Hawaii during a search for near-Earth asteroids. We’ve put telescope resources on Earth and in space on the object, but our observing time is up.

For ‘Oumuamua is now well on its way out of the Solar System, so we’re left to massage the data we have in hopes of gaining new insights. Davide Farnocchia (Center for Near Earth Object Studies, JPL) encapsulates the issue:

“Usually, if we get a measurement from a comet that’s kind of weird, we go back and measure it again until we understand what we’re seeing. But this one is gone forever; we probably know as much about it as we’re ever going to know.”

Thus Avi Loeb’s recent paper with Shmuel Bialy discussing the object’s acceleration in terms of solar radiation pressure — could it be a technological artifact? — and continued work on the issue of cometary outgassing to explain its anomalous acceleration. See ‘Oumuamua, Thin Films and Lightsails for the former. On the latter, we have new work from the abovementioned Farnocchia, working with lead author David Trilling (Northern Arizona University) and colleagues in a paper published in The Astronomical Journal.

Trilling and team examine data from the Spitzer Space Telescope taken in November of 2017, an analysis that shows that the object was too faint for Spitzer to detect when it began observations two months after ‘Oumuamua’s closest approach to the Sun in September of that year. That fact is itself valuable, for it sets limits on the object’s total surface area. The size issue is important, because an earlier study led by ESA’s Marco Micheli (citation below) found the object’s acceleration to be the result of outgassing, which worked, according to the team’s calculations, by assuming that ‘Oumuamua was smaller than typical Solar System comets (see ‘Oumuamua: New Data Point to a Comet).

Image: Is this the shape of ‘Oumuamua? An artist’s concept of interstellar asteroid 1I/2017 U1 (‘Oumuamua) as it passed through the solar system after its discovery in October 2017. Observations of ‘Oumuamua indicate that it must be very elongated because of its dramatic variations in brightness as it tumbled through space. Credit: European Southern Observatory / M. Kornmesser.

So what constraints can we apply from the Spitzer data? Spitzer works in the infrared, adding valuable adjunct information to the variations in ‘Oumuamua’s brightness already detected by ground-based telescopes and the Hubble space instrument. These changes in brightness suggested an object less than 800 meters in its longest dimension. Unable to determine shape, the Spitzer data can only set a limit on the object’s total surface area. Thus the authors plug a spherical shape into their calculations and use three different models to reach their conclusions.

With different inputs for its composition, ‘Oumuamua’s non-detection in the infrared implies a ‘spherical diameter’ ranging from a high of 440 meters to a low of 100 meters. The results are consistent with Micheli and team’s findings on the object’s likely size assuming outgassing. Again, the range is the result of different assumptions about the object’s composition, which is unknown. This JPL news release adds that, weighing infrared findings against optical observations, ‘Oumuamua may be up to 10 times more reflective than comets in our Solar System.

A comet warms as it approaches perihelion, with ice vaporizing and cleansing the surface dust and dirt to expose more reflective ice beneath. As with comets we have observed before, outgassing can also produce a new coating of ice and snow, adding to the object’s albedo after close solar passage. This kind of outgassing could have occurred during perihelion for ‘Oumuamua about five weeks before its discovery. Did we subsequently see a dark surface with millions of years of accumulated dust being swept away by released gases and covered in new snow?

The paper is Trilling et al., “Spitzer Observations of Interstellar Object 1I/’Oumuamua,” The Astronomical Journal Vol. 156, No. 6 (14 November 2018). Abstract. The Micheli paper is “Non-gravitational acceleration in the trajectory of 1I/2017 U1 (‘Oumuamua),” Nature 559 (27 June 2018), 223-226. Abstract. The Bialy & Loeb paper is “Could Solar Radiation Pressure Explain ‘Oumuamua’s Peculiar Acceleration?” (preprint).


{ 57 comments… add one }
  • ljk November 15, 2018, 15:45

    The Strange Case of 1I/’Oumuamua

    November 11, 2018

    Mark Kidger


    To quote:

    More plausible than the light sail would be a monolith-shaped structure like TMA-1 from “2001 a Space Odyssey”, which would be susceptible to light pressure and, if tumbling, would produce the high-amplitude light curve. It is difficult though to understand how this could be a natural object and how it could come to visit us.

  • Alex Tolley November 15, 2018, 16:20

    One possible scenario that appears to explain
    many of the observed properties of ‘Oumuamua, including our
    observations, is exposure or creation, from outgassing, of a
    fresh, icy, bright surface due to thermal reactivation during
    ‘Oumuamua’s close perihelion passage in 2017 September.

    I like this explanation as it could explain the unusual shape of the object that was inferred from the light curves. If an outgassing area created a localized, relatively high albedo spot on the surface, this would exaggerate any light curve values. As much of the object’s “mystery” hinged on its unusual shape, it may well be that its shape is much less oblate, but with a non-uniform surface albedo. If the acceleration requires outgassing, then this seems like a more reasonable explanation that some exotic (I would say unwarranted) explanation based on a technological artifact, like a light sail.

    While it may be fun to speculate that this is some sort of Rama-like artifact, the data we have is insufficient to characterize the object beyond some basic constraints. We should accept this for now. If we get more data from some future mission, then that may explain this object. Until then, we should just accept that it is most likely a comet or Oort type object that possibly has come from another star system.

    If nothing else, it suggests that other such interstellar wanders might well be transiting our system and are worth looking out for.

    • Harry R Ray November 16, 2018, 10:33

      The only bugaboo left toward a natural solution is, even if `Oumuamua is very small, perfectly spherical, and has “spots” with VASTLY DIFFERENT ALBEDOS, it is still TUMBLING! Outgassing will cause it to SPIN UP, according to Rafikov(although the above scenario entails that it would NOT break apart)which it obviously DIDN’T!!!!! The only one way out of these irreconcilable data sets is to prove, somehow, that `Oumuamua is NOT tumbling!!!!! I have relegated the non-natural “light-sail” hypothesis to the dust bin due to the Spitzer observations, so I will have to check out ljk’s low density “monolith” model, for it now seems to be the only viable “non-supercontrived” non-natural solution left!

      • Alex Tolley November 16, 2018, 14:53

        Why the assumption that high albedo spots imply outgassing and hence possible spin up? The bright spots may be inactive, possible impact sites exposing lighter material. All natural explanations should be pursued and eliminated before unnatural ones.

        • Harry R Ray November 18, 2018, 14:27

          OK. If that’s the case, where did the non-gravitational acceleration come from?

    • Hamilton1 November 16, 2018, 13:50

      Dr Meech has dealt with the albedo/elongation query, stating that a lightcurve caused by shape will have different characteristics than a lightcurve caused by albedo :


  • Robin Datta November 15, 2018, 17:03

    Short on data, long on speculation, soft on conclusions. Interesting nevertheless!

  • Harry R Ray November 16, 2018, 12:02

    I’ve finally figured EVERYTHING out(including the PURPOSE of `Oumuamua)in a flash of utter brilliance! A cloaking device in the INFRA-RED ONLY, leading to optical observations and ir non-detection producing irreconcilable data sets which eventually cause everyone on the planet to go utterly bleeping MAD!!!!!

    • Michael November 16, 2018, 14:23

      Now that is Interesting, How is the coffee consumption going anyway?

      • Manel Martins November 16, 2018, 17:22

        Through the roof, it’s from Kenya, damn good.

  • ljk November 16, 2018, 14:08

    If organic life does decide to explore the galaxy, it may do so via its mechanical proxies, just as our first explorers of the Sol system were all robotic.


    Life Before Fermi – Back to the Solar System

    David L Clements

    (Submitted on 15 Nov 2018)

    The existence of intelligent, interstellar traveling and colonising life is a key assumption behind the Fermi Paradox. Until recently, detecting signs of life elsewhere has been so technically challenging as to seem almost impossible. However, new observational insights and other developments mean that signs of life elsewhere might realistically be uncovered in the next decade or two.

    We here review what are believed to be the basic requirements for life, the history of life on Earth, and then apply this knowledge to potential sites for life in our own Solar System.

    We conclude that the necessities of life – liquid water and sources of energy – are in fact quite common in the Solar System, but most potential sites are beneath the icy surfaces of gas giant moons.

    If this is the case elsewhere in the Galaxy, life may be quite common but, even if intelligence develops, is essentially sealed in a finite environment, unable to communicate with the outside world.

    Comments: Accepted for publication in the Journal of the British Interplanetary Society

    Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

    Cite as: arXiv:1811.06313 [astro-ph.EP]
    (or arXiv:1811.06313v1 [astro-ph.EP] for this version)

    Submission history

    From: David L. Clements [view email]

    [v1] Thu, 15 Nov 2018 12:27:44 UTC (116 KB)


  • Patient Observer November 16, 2018, 15:56

    Curious if Oumuamua’s trajectory has been sufficiently defined to allow a future mission to rendezvous with it long after it is out of range of all earth and space-based sensors. The probe would need some pretty good sensors of its own plus a significant ability to change direction and velocity to optimize the flyby.

  • Bruce D. Mayfield November 16, 2018, 17:01

    What I cannot get is why if it, if it’s movement is changing simply do to cometary outgassing on it’s way out and rapidly cooling off, how could there be no detectable outgassing when it was closer to the Sun and warmer???

    • Paolo November 20, 2018, 12:56

      Sir, ‘this the first issue that I envisaged… could someone please answer?

      • Bruce D. Mayfield November 21, 2018, 1:48

        I rephrased my question on today’s APOD discussion page and got a reasonable answer:

        BDanielMayfield wrote: ↑Tue Nov 20, 2018 8:27 am
        “I want to accept “the leading natural hypothesis” of comet like out gassing, but I’m sort of hung up on this question: If it was just from natural heating, why was no cometary activity noticed when it was closer to the sun and therefore much warmer than it is now?”

        Chris Peterson answered: “It’s a very, very low level of outgassing required to produce this extremely small deviation in orbit. Well below what would produce any sort of obvious tail or coma without carefully looking for it… something which was not anticipated and which we had very little time for.”

  • Mark November 16, 2018, 22:19

    Just curious, with all this analysis at infrared, radio, and UV electromagnetic wavelengths generating nothing but confusion, did anyone think to look for the obvious? Didn’t any scientist anywhere listen on the 3kHz-20kHz audio band for the calls of hump back whales?

    • Harry R Ray November 21, 2018, 11:16

      DOI: 10.1098/rsbp.2018.2088. Humpback whales compose new communal songs every few years. So that’s why it has to keep coming back and back and back!

  • Rob Flores November 17, 2018, 2:00

    Let me try and give alternate explanations for the measurements and
    observations of the object : since it has a pandora like pull on Earthlings.

    This is a low technology crewed interstellar survey mission probe ship Close to or just exceeding to our technical capabilities. The reason they sent the probe is to settle a religious argument. But they are not in a hurry to answer it.

    These beings are longed lived and can naturally hibernate. They have
    a natural lifespan of 300 yrs, and have perfected a deeper hibernation.
    The controllers that sent them are also hibernating in this mode on their home world which is about 200 LY away. The reason they sent the probe is to settle a religious argument.

    If the probe detects advanced inter system space infrastructure, it sets a new course to an alternate destination. Only G and K, stars are surveyed, and they are picked by the potential bio signature of a solar system. So far they have surveyed 7 systems, and have found 1 other with animal life but no technology.

    The probe only begins to rotate [for gravitational and systems operations], when it approaches within 500 AU of
    a solar system in their path. Part of crew is awaken for preparation of
    the ship for equipment and more scheduled crew revivals.

    At 100AU a protective coating is extruded on its surface to deal with in system minor dust and debris.

    The survey lasts 10 days in a stars habitable zone, after this 2/3 of the crew place themselves in natural hibernation.

    Large reserves of power were used in the operation up to this point.
    and there is recharging to be done. The charging process is coupled
    with the expulsion of waste gases. These gases are fairly hazardous to the ship, so is uses these waste products as reaction mass, to speed the ship away from the cloud. There is also another extrusion to the surface since the charging process degrades the old extrusion. at the time of full charge 95 of the crew are placed into deep hibernation. The remaining crew pick from choice of several candidates a new destination. this path in the general direction of The Turning Space
    a low mass black hole, that in conjunction with a second and a jaunt
    to a A class star, will send them on a near return to origin after more than 1,000 Ly of travel. Although not in a hurry, the opposing sides of the religious question really do want answer that is why the mission
    has a limited endurance, and these beings do not believe in suicide or suicide missions.

  • Michael Fidler November 17, 2018, 16:54

    So maybe it was alive.

    Quantum Biology: Spooky, Mysterious, and Fundamental to Life Itself.

    As little as a decade ago, scientists were sure that the chemistry of life and the weird chemistry of the quantum world were completely separate things. Quantum effects were usually observed only on the nanometer scale, surrounded by hard vacuum, ultra-low temperatures, and a tightly controlled laboratory environment. Biology, however, is a macroscopic world that is warm, messy, and anything but controlled. It seemed elementary that a quantum phenomenon such as ‘coherence’, in which the wave patterns of every part of a system stay in step, wouldn’t last a microsecond in the tumultuous realm of the cell. It would be simply unthinkable.

    Or so we thought…

    Recent years have seen scientists finding coherent quantum processes all across the natural world. And it’s not just in some exotic halobacteria or flying marsupial, it turns out quantum biology is pretty much ubiquitous. In fact, it appears to be a central part in the most important chemical reactions on Earth: photosynthesis and cellular respiration.


  • Leo November 19, 2018, 4:56

    So…A few things.

    Why are all pictures (artist’s) still cigar shaped? If NASA updated, and it was ‘spherical’ and 5-10 sheet-thick, any artists updating, please? :)

    Also, didn’t the Harvard fellow say acceleration occurred three times? (Reasoning against the outgassing, apparently)

    Perhaps, IF Oumuamua were artificial, it really was just doing its own thing with no intent on surveying us.

    Think about it. Say you’re urgently trying to find a loved one (or on some urgent mission, whatever floats your boat) etc., you aren’t really going to pay attention to anything else as you (or your drone that you sent out) focus on your priority objective.

    As important as we think we are (the center of everything etc), maybe it just needed to get where it needed to go and ‘borrowed’ our sun. Maybe it’s civilization was about to go extinct and needed to find ‘Vibranium’ or whatever.

    Finally, artificial or not all I gotta say is at the speed that thing was going we need to spot these better before the next one coincidentally hits anything in our solar system!

    • ljk November 20, 2018, 10:22

      Because the media likes to use the same artwork over and over. Look up news items on rogue planets and you will see the same blue gas giant with the Milky Way in the background, over and over. Exoplanet art does not fare much better.

  • ljk November 19, 2018, 13:26

    Oumuamua mystery continues: Interstellar object could be just a millimeter thick

    By Nirmal Narayanan

    November 18, 2018 13:48 +08


    However, Seth Shostak revealed that there will be n number of objects like Oumuamua outside the solar system. He argues that Oumuamua has not caught our attention just because it entered the solar system.

    “This implies a number of these things are drifting through the cosmos, as ubiquitous as fire hydrants. Unless a miracle has occurred, these are entering our solar system all the time. This is just the first one we’ve found,” said Shostak.

    Shostak also made it clear that Oumuamua could be most likely a weird rock, and he ruled out the possibility of this object being an alien ship.

    “If they really wanted to target our solar system, they’d hang around longer and probably come closer to the earth,” clarified Shostak.

    [Assuming these ETI are focused on Earth as their target. There are other worlds in our Sol system which could easily be more fascinating and/or especially useful to starfaring aliens. Once again humans think they are the Focus of Existence despite all the evidence to the contrary.]

    • Harry R Ray November 20, 2018, 11:13

      Thanks ljk. Right after I consigned the “lightsail”, to the scrapheap, you and Seth Shostak rock my world!!!!! So, here we go again. A DUAL purpose for `Oumuamua! 234 alien civilizations(yes, I’m back to THAT again, until somebody proves it WRONG once and for all)manufacture Von Neumann machines that can rapidly reproduce ~100 meter lightsails exponentially so that over a billion years or so, up to 1,000,000,000,000,000 of them will exist!!!!! In a million years or so, every solar system, rogue exoplanet and rogue exomoon will be studied by replicated probes. After all of this information has been returned to the 234 ET’s, a massive project begins to create laser arrays orbiting 234 stars(one for each civilization) which are NOT the ET’s homestar. These laser arrays start to broadcast picosecond pulses to stars where the ETs deem future intellegent life may develop. After this occurs, commands are sent to the Von Neumann machines to CEASE reproduction of probes and 0.3mm lightsails. the probes and lightsails become RELICS, destined to orbit within the galaxy INDEFINITELY. Over billions of years, the recently discovered “space grease” builds up on the now PROBELESS lightsails, increasing their width to 1mm, rendering them extremely(but not TOTALLY)inefficient. Thus by sheer CHANCE, and NOT by DESIGN, `Oumuamua encountered our solar system in the way that it did. At perihelion, some, but not all of the “space grease” boiled off, which caused `Oumuamua to start tumbling, producing a very small and asymetric acceleration phase which appears in THREE SEPARATE INSTANCES, and then stops when it extreme inefficiency becomes total inefficiency. The TRUE REVELATION here, is that the 234 ETs would know this would happen over and over again, making them PERFECT HARBINGERS for the ETs’ existance!!!!!

      • ljk November 20, 2018, 12:21

        And going along with your speculation, we may also assume there could be more than one ETI launching VN probes. So going along these lines, maybe we should be seeing a lot more of these. Which in this case just shows how behind humans are when it comes to searching for alien probes or interstellar objects in general.

        • Bruce D. Mayfield November 21, 2018, 1:58

          Thus, ‘where are everybody’s VN probes,’ ye old Fermi paradox restated.

          • Harry R Ray November 21, 2018, 10:35

            As I stated in my comment above, if my speculation is right, the high volume visitations happened billions of years ago, when only microbial life existed on Earth. When “visitations” happen now, they are merely the “scrap” left over from the prior epoch of high intensity visitations, and thus are much more random and much less common. To sum up where we are now, one of the main SETI people(Seth Shostak)has been moved HALF WAY to a non-natural interpretation for `Oumuamua by another of the main SETI people(Avi Loeb)because of the plausibility of of the “solar propulsion” argument and the problems with the “outgassing” argument. To move him further, we need to know the recriminations of such a close perihelion passage on his NATURAL 1mm thick, 100m+x100m+ “space rock”. Supercomputer time, anybody?

  • ljk November 20, 2018, 10:33


    Astronomy Picture of the Day

    Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

    2018 November 20

    The Unexpected Trajectory of Interstellar Asteroid ‘Oumuamua

    Image Credit: NASA, JPL, Caltech

    Explanation: Why is ‘Oumuamua differing from its expected trajectory? Last year, 1I/2017 U1 ‘Oumuamua became the first known asteroid from interstellar space to pass through our Solar System.

    Just over a year ago, this tumbling interstellar rock even passed rather close to the Earth. The asteroid’s future path should have been easy to predict given standard gravity — but ‘Oumuamua’s path has proven to be slightly different.

    In the featured animation, ‘Oumuamua is shown approaching and exiting the vicinity of our Sun, with the expected gravitational and observed trajectories labelled.

    The leading natural hypothesis for this unexpected deviation is internal gas jets becoming active on the Sun-warmed asteroid — but speculation and further computer simulations are ongoing.

    ‘Oumuamua will never return, but modern sky monitors are expected to find and track similar interstellar asteroids within the next few years.

  • ljk November 21, 2018, 13:54

    6 Strange Facts about the Interstellar Visitor ‘Oumuamua

    By Abraham Loeb on November 20, 2018


    To quote:

    1. Assuming that other planetary systems resemble the solar system, Pan-STARRS should not have discovered this or any other interstellar rock in the first place. In a paper published a decade ago, we predicted an abundance of interstellar asteroids that is smaller by many (two to eight) orders of magnitude than needed to explain the discovery of ‘Oumuamua, assuming it’s a member of a random population of objects. Put another way, ‘Oumuamua implies that the population of interstellar objects is far greater than expected. Each star in the Milky Way needs to eject 1015 such objects during its lifetime to account for a population as large as ‘Oumuamua implies. Thus, the nurseries of ‘Oumuamua-like objects must be different from what we know based on our own solar system.

    5.The Spitzer Space Telescope did not detect any heat in the form of infrared radiation from ‘Oumuamua. Given the surface temperature dictated by ‘Oumuamua’s trajectory near the sun, this sets an upper limit on its size of hundreds of meters. Based on this size limit, ‘Oumuamua must be unusually shiny, with a reflectance that is at least 10 times higher than exhibited by solar system asteroids.

    The extra push exhibited by ‘Oumuamua’s orbit could not have originated from a breakup into pieces because such an event would have provided a single, impulsive kick, unlike the continuous push that was observed. If cometary outgassing is ruled out and the inferred excess force is real, only one possibility remains: an extra push due to radiation pressure from the sun. In order for this push to be effective, ‘Oumuamua needs to be less than a millimeter thick but with a size of at least 20 meters (for a perfect reflector), resembling a lightsail of artificial origin. In this case ‘Oumuamua would resemble the solar sail demonstrated by the Japanese mission IKAROS or the lightsail contemplated for the Starshot initiative. An artificial origin offers the startling possibility that we discovered “a message in a bottle” following years of failed searches for radio signals from alien civilizations. Reassuringly, such a lightsail would survive collisions with interstellar atoms and dust as it travels throughout the galaxy.

    • Michael Fidler November 22, 2018, 6:20

      Well that article pretty much sums it up. It must of escaped from our little box and now that it is out of the box it has created pandora’s paradox. Just what you would expect from ET to teach the children without breaking Fermi’s paradox… ;>})

    • Harry r Ray November 23, 2018, 10:39

      Funny that he mentioned ONLY Spitzer in the gas/dust NON-DETECTION. The conventional “wisdom”(THAT word taken with a HUGE grain of salt by me) is now that the gas was NOT carbon dioxide, but; instead, water vapor. Obviously they are using this as a fallback position until they can find something “better”. The problem with this is that Loeb’s own sponsor, Breakthrough Initiatives, used the Green Bank radio telescope to look for evidence of water(ice ON the object AND water vapor AROUND it(while it was simultaneously searching for artificial radio signals)and found NOTHING! ZIP, ZERO, NADA! All that’s left is N2. Can’t wait till they try to rationalize THAT ONE! Oh, and by the way, Breakthrough Initiatives has NOT YET completed its IN-DEPTH final analysis of its radio signal,either. I hope they are capable of extracting FRB-like(in terms of signal DURATION anyway)”chirps” from the data, if there are any there to extract.

      • ljk November 26, 2018, 10:43

        Most of the Breakthrough Initiatives senior members are from the old guard SETI and related fields. I will be more than surprised if they find or admit to anything other than “business as usual”.

        Aliens are a messy business for most humans, especially and ironically those who have appointed themselves as the ones to find them.

        • ljk December 3, 2018, 10:52

          Allow me to amend my above statement. When it becomes necessary to admit to the existence of alien intelligences, then they will “find” some. Just as Green Bank used to disavow their pioneering SETI work until NSF cut their funding. Now they offer public tours of their glorious SETI history – which was mainly letting Frank Drake conduct Project Ozma for several months, where he examined two nearby Sol-type suns via radio waves and detected a U-2 spy plane.

      • Harry R Ray November 28, 2018, 11:16

        Speaking of FRB’s: ArXiv.org: 1811.10748. “FRB 121102 Shows Complex Time-Frequency Structure.” by J. W. T. Hessels et al. Sub-bursts WITHIN the bursts have now been detected with typical bandwiths of 100 to 400 MHz and drift rates of ~200 MHz for LOWER FRB 121102 frequencies. This could DIFFERENTIATE true FRB’s from “peryton-like” FRB’s POSSIBLY emminating from objects like `Oumuamua.

    • Harry R Ray November 27, 2018, 11:36

      The PDF is now available on ArXiv in the “cross-listings” section as ArXiv.org: 1811.08832. He gives a MUCH STRONGER ARGUMENT for `Oumuamua being a lightsail than just a 1mm thick sheet of “rock”(i.e. either carbon or silica based objects)than in the paper mentioned in this blog. Basically, his argument goes, that unless. ONE: Every star ejects ten to the fifteenth power objects(as stated above)with a velocity UNIQUELY PROPORTIONAL(NOT stated above), PANSTARRS should never have detected it, and; TWO: Even if “ONE” were to be the case, the great majority of these natural objects must have its major axis be at least 20 meters long, if it were perfectly reflective, and much longer if it were ten times more reflective than “average” comets(i.e. ~30%. He uses the word “asteriods” instead of comets, but I think that is in error)AND be ONLY 1mm thick!!!!! If you remember, Kipping et al deduced a baysian number of 400,000 to describe the likely(if all assumptions and interpretations of all the data are correct)probability of an exomoon causing Kepler 1625b’s TTV’s as opposed to another planet being the cause. Loeb(or someone else)should deduce the baysian number for the likely probability of `Oumuamua being a lightsail as opposed to an extremely long, very wide, 1mm thick natural object based on all of his arguments above. I bet his baysian number would be much MUCH larger than Kipping’s!

      • ljk December 3, 2018, 10:55


        Six Strange Facts About `Oumuamua

        Abraham Loeb (Harvard)

        (Submitted on 21 Nov 2018 (v1), last revised 22 Nov 2018 (this version, v2))

        `Oumuamua is nothing like we expected or seen before in the Solar System.

        Comments: Published in Observations, Scientific American (November 20, 2018); this https URL

        Subjects: Popular Physics (physics.pop-ph); Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)

        Cite as: arXiv:1811.08832 [physics.pop-ph]
        (or arXiv:1811.08832v2 [physics.pop-ph] for this version)

        Submission history

        From: Avi Loeb [view email]

        [v1] Wed, 21 Nov 2018 17:17:13 UTC (316 KB)
        [v2] Thu, 22 Nov 2018 20:09:02 UTC (316 KB)


  • Michael Fidler November 22, 2018, 6:38

    I’m sure it is just a ten dimensional pyramid having 3 body problems.

    • Michael C. Fidler November 27, 2018, 6:46

      Identifying Interstellar Objects Trapped in the Solar System through Their Orbital Parameters.

      “The first interstellar object, `Oumuamua, was discovered in the Solar System by Pan-STARRS in 2017, allowing for a calibration of the abundance of interstellar objects of its size and an estimation of the subset of objects trapped by the Jupiter-Sun system. Photographing or visiting these trapped objects would allow for learning about the conditions in other planetary systems, saving the need to send interstellar probes. Here, we explore the orbital properties of captured interstellar objects in the Solar System using dynamical simulations of the Jupiter-Sun system and random initial conditions. We compare the resulting distributions of orbital elements to those of the most similar population of known asteroids, namely Centaurs, to search for a parameter space in which interstellar objects should dominate and therefore be identifiable solely by their orbits. We find that there should be hundreds of `Oumuamua-size interstellar objects identifiable by Centaur-like orbits in polar or retrograde motion. We note four known objects that may be of interstellar origin. Finally, we estimate that LSST will be able to detect several tens of these objects.”

      “We simulated the capture of interstellar objects with an initial speed v∞ ∼20 km s−1 outside the Solar System by means of three-body interactions with the Jupiter-Sun system.”


      A universe of 10 dimensions.


      Here’s a Visual Guide to the 10 Dimensions of Reality.


      The brilliant physicist Richard Feynman (1918-1988) famously thought so, saying there is a number that all theoretical physicists of worth should “worry about”. He called it “one of the greatest damn mysteries of physics: a magic number that comes to us with no understanding by man”.

      That magic number, called the fine structure constant, is a fundamental constant, with a value which nearly equals 1/137. Or 1/137.03599913, to be precise. It is denoted by the Greek letter alpha – α.

      • Michael C. Fidler December 1, 2018, 7:22

        Has anybody done an analysis for these four asteroids orbits; 2011 SP25, 2017 RR2, 2017 SV13, and 2018 TL6 to see if any of them will have an occultation of a bright star?

        Table 1. Orbital parameters for possible trapped interstellar objects, namely semi-major axis, a, eccentricity, e, inclination, i, orbital period, T, perihelion distance, q, and aphelion distance, Q.
        Candidate a (AU) e i (deg) T (yr) q (AU) Q (AU) H
        2018 TL6 8.26 .79 170.9 23.76 1.72 14.8 19.9
        2017 SV13 9.65 .79 113.2 29.99 2.01 17.3 18.2
        2011 SP25 19.54 .88 109.1 86.35 2.27 36.8 16.8
        2017 RR2 23.65 .89 89.1 115 2.63 44.7 17.5

        • Harry R Ray December 3, 2018, 10:43

          Surprising they did not mention 2015 BZ 509, the 3 km retrograde Jupiter co-orbital non-trojan asteroid that another group of astronomers previously touted as being of extra-solar origin.

  • Michael C. Fidler November 27, 2018, 6:57

    Variations in fine-structure constant suggest laws of physics not the same everywhere.

    “While the data from just one telescope seemed to suggest that alpha varies in time, data from the two telescopes show that alpha also seems to vary in space. Such a discovery could have major implications, starting with shattering the basic assumption that physical laws are the same everywhere in the universe. The results also violate the Einstein Equivalence Principle, and suggest that the universe may be much larger than currently thought – or even infinite in size.”

    Read more at: https://phys.org/news/2010-09-variations-fine-structure-constant-laws-physics.html#jCp

    Well, it just may of popped in from somewhere else…

    Halton Arp, God bless his Soul. :-]

  • Harry R Ray November 27, 2018, 13:53

    Paul Gilster: A new `Oumuamua “team” featuring @jedicke, @astrokiwi, @colinsnodgrass, @Sraymond_astro has been formed and had its first formal meting yesterday. Sean Raymond is the only one I am reasonably familiar with. What did they discuss yesterday, and what do they eventually plan to achieve? A guest post from them a few months from now would be extremely exciting, ESPECIALLY if they find a solution to the tumbling/non-gravitational acceleration/no spin-up conundrum!

  • Patrick Underwood December 1, 2018, 17:03

    This is an idea I ran by Paul in a PM, and his response was skeptical but encouraging, so l am posting it here.

    Suppose Oumuamua really is a spacecraft, and started its trip into the inner Solar System from a larger spacecraft (“Oumuamua-Mama” you might call it) in a large Solar orbit. For simplicity, assume a circular orbit. Given Oumuamua’s trajectory, and assuming an eventual rendezvous with Oumuamua-Mama, wouldn’t it be possible to determine the parameters of that orbit? Giving us definite areas to look for anything anomalous, and a date range for the rendezvous.

    If the orbit is not circular or is hyperbolic, I guess things get a lot more difficult. But it’s a place to start.

    My (probably faulty) intuition based on a long-ago orbital mechanics course leads me to think there is only one circular Solar orbit that would intersect Oumuamua on both its inbound and outbound courses.

    Even with the simplifying constraint of a circular orbit, there are complicating variables–for example, the time over which delta-v is applied to Oumuamua for the departure and rendezvous maneuvers.

    Would anyone here be kind enough to determine whether a) this is possible and subject to analysis, or b) I’m out of my depth?

    • Bruce D. Mayfield December 2, 2018, 1:39

      I’m no orbital mechanic Patrick but if O-Mama was in a distant solar orbit its motion would be have to be small compared to that of it’s supposed probe. It isn’t like ‘Oumuamua made a tight U turn ’round the Sun, it was something more like a 90 degree turn, therefore the supposed launch and retrieval intersections would be very widely separated, many AU’s apart.

      • Patrick Underwood December 2, 2018, 21:14

        Yes. I would expect a near-linear flyby of the “mothership.” It just seemed like a simpler exercise to posit something solvable, rather than Bruce’s infinite set of integral fields! But I was definitely thinking of a very large orbit, perhaps beyond the Kuiper belt or even further out. I mean, starship and all… :)

    • Bruce D. Mayfield December 2, 2018, 2:24

      Now, while Patrick’s large circular solar orbit idea for O-Mama might be out because the math wouldn’t work, it occurred to me that there really are an INFINITE number of possible solutions in which an interstellar mothership just passing our system by might shoot an HZ probe down into our space on a path for later retrieval on the way out. That sounds like the kind of thing we might do one day. Stays within the bounds of the PRIME DIRECTIVE too ;)

      • ljk December 3, 2018, 10:36

        And they probably dropped off a whole bunch of nanoprobes all over the place along the way. Hey, we know CubeSats work in deep space now so why not? :^)

  • ljk December 3, 2018, 10:34

    November 30, 2018, 11:37 pm

    Astronomers Are Tracking Four Potential Interstellar Objects Now In Our Outer Solar System

    Bruce Dorminey Contributor

    Using detailed computer models of asteroidal-type objects between the Sun and Jupiter, two Harvard University researchers find that at least four known objects are likely to have origins from outside our solar system.

    After becoming gravitationally-trapped, the four potentially interstellar objects — 2011 SP25, 2017 RR2, 2017 SV13, and 2018 TL6 — are thought to spend most of their time between the orbits of Jupiter and Neptune. However, during their closest approaches to the Sun, they do pass through Earth’s neighborhood.

    In a paper submitted to the Monthly Notices of the Royal Astronomical Society, Harvard co-authors Amir Siraj and Abraham Loeb, compare the orbital characteristics of theoretical high-inclination objects to those of the centaurs, the most similar population of known asteroids.

    “We find that there should be hundreds of Oumuamua-size interstellar objects identifiable by Centaur-like orbits,” write the authors. 1I/2017 U1 Oumuamua, the first bona fide interstellar object, was discovered Oct. 19, 2017 by the University of Hawaii’s Pan-Starrs telescope. But the authors note that there should be at least 66 possible other interstellar objects in their calculations, ranging in diameter from roughly 100 meters to 10 kilometers in size.

    Full article here:


    To quote:

    As for the four that the authors have thus far identified as potential interstellar objects?

    “ We do not know if they are comets, asteroids, or artifacts ,” Amir Siraj, a Harvard University undergraduate in astrophysics, told me. Until these objects pass close to earth again, he says we won’t be able to know. Siraj notes that of the four, object 2018 TL6 will make a close Earth approach in another twenty years.

    Could they be artificial in origin?

    “We do not have any evidence that these [four] objects are unnatural at this point,” said Siraj.

    They pass near Earth on timescales of some 20 to 120 years so it will be another 20 years until we can photograph one of them, he says. That is, unless someone designs a flyby mission that will visit one or more of them. The most likely source of interstellar objects is planetary systems that eject them during formation and development processes.

    And as for Oumuamua which NASA classifies as a highly-elongated, rocky, cigar-shaped object with a somewhat reddish hue?

    NASA’s Spitzer infrared telescope data rules out typical cometary activity, says Loeb. And he says it also sets an upper limit on Oumuamua’s size, which in turn implies a shiny surface, which is at least ten times more reflective than a typical asteroid.

    “These results are at odds with the properties of comets and asteroids in the solar system are fully consistent with an artificial origin,” said Loeb.

    • ljk December 3, 2018, 10:44

      The paper mentioned above:


      Identifying Interstellar Objects Trapped in the Solar System through Their Orbital Parameters

      Amir Siraj, Abraham Loeb

      (Submitted on 23 Nov 2018 (v1), last revised 27 Nov 2018 (this version, v2))

      The first interstellar object, `Oumuamua, was discovered in the Solar System by Pan-STARRS in 2017, allowing for a calibration of the abundance of interstellar objects of its size and an estimation of the subset of objects trapped by the Jupiter-Sun system.

      Photographing or visiting these trapped objects would allow for learning about the conditions in other planetary systems, saving the need to send interstellar probes.

      Here, we explore the orbital properties of captured interstellar objects in the Solar System using dynamical simulations of the Jupiter-Sun system and random initial conditions. We compare the resulting distributions of orbital elements to those of the most similar population of known asteroids, namely Centaurs, to search for a parameter space in which interstellar objects should dominate and therefore be identifiable solely by their orbits.

      We find that there should be hundreds of `Oumuamua-size interstellar objects identifiable by Centaur-like orbits in polar or retrograde motion.

      We note four known objects that may be of interstellar origin. Finally, we estimate that LSST will be able to detect several tens of these objects.

      Comments: 5 pages, 4 figures, 1 table, submitted to MNRAS

      Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

      Cite as: arXiv:1811.09632 [astro-ph.EP]
      (or arXiv:1811.09632v2 [astro-ph.EP] for this version)

      Submission history

      From: Amir Siraj [view email]

      [v1] Fri, 23 Nov 2018 19:00:02 UTC (565 KB)
      [v2] Tue, 27 Nov 2018 19:25:21 UTC (853 KB)


  • Harry R Ray December 3, 2018, 11:25

    One of the main arguments I have made for a non-natural state of being for `Oumuamua is its uniqueness. I have made similar arguments for other objects, such as Przybylski’s Star, and the objects orbiting Boyajian’s star. Now, it appears that the latter may not be so unique after all. Objects orbiting VVV-WIT-07, EPIC 235240266, and EPIC 205718830 appear quite similar to those blocking light from Boyajian’s Star, although blockages of light from the two EPIC stars have not yet exceeded 1%, and it is yet to be determined whether VVV-WIT-07 is or is not a main sequence star. Stay tuned.

  • Harry R Ray December 5, 2018, 11:10

    “Comet 67p/Churyumov-Geraimenko rotation changes derived from Sublimation induced torques.” by Tobias Kramer, Matthias Laeuther, Stubbe Hviid, Laurent Jorda, Horst Uvve Keller, Ekehard Kuhrt. Could sublimation of a “space grease” coating at perihelion passage have INDUCED `Oumuamua’s chaotic tumbling?

  • ljk December 5, 2018, 18:16


    A Radio Search for Artificial Emissions from ‘Oumuamua

    December 4, 2018

    “We were looking for a signal that would prove that this object incorporates some technology …”

    MOUNTAIN VIEW – It’s the first time a visitor from another star system has been seen nearby. But what is it? An asteroid, a comet … or an alien artifact?

    Scientists at the SETI Institute have attempted to address this question by using the Allen Telescope Array (ATA) to observe ‘Oumuamua when it was about 170 million miles away, or slightly less than the diameter of Earth’s orbit. The intention was to measure artificial radio transmissions which, if found, would be strong evidence that this object is not simply a rock tossed into space by a random gravitational slingshot interaction that occurred in its home star system.

    “We were looking for a signal that would prove that this object incorporates some technology – that it was of artificial origin,” says Gerry Harp, lead author of a paper to be published in the February 2019 issue of Acta Astronautica. “We didn’t find any such emissions, despite a quite sensitive search. While our observations don’t conclusively rule out a non-natural origin for ‘Oumuamua, they constitute important data in accessing its likely makeup.”

    Following its discovery in October 2017, Oumuamua was the subject of popular speculation about a possible non-natural origin largely because it brought to mind the interstellar spaceship in Arthur C. Clarke’s novel Rendezvous with Rama. Its highly elongated shape and the fact that no coma was observed strengthened this hypothesis for some, as these are uncharacteristic of asteroids and comets.

    A recent paper published in Astrophysical Journal Letters by researchers at Harvard has also suggested the possibility that Oumuamua is a deliberate construction. The Harvard researchers argue that the slight, unexpected acceleration observed for this object could be caused by pressure from sunlight as Oumumua swung around the Sun. Their hypothesis is that the object might be a light sail, either deliberately or accidentally sent our way. A deliberate origin is considered somewhat more likely because our solar system is a very small target for any object that is not being aimed.

    Such arguments strengthen the importance of observations such as those conducted on the ATA that can constrain the true nature of Oumuamua.

    Observations were made between November 23 and December 5, 2017, using the wide-band correlator of the ATA at frequencies between 1 and 10 GHz and with a frequency resolution of 100 kHz. No signals were found at a level that would be produced by an omnidirectional transmitter on-board the object of power 30 – 300 milliwatts. In portions of the radio spectrum that are routinely cluttered by artificial satellite telemetry, the threshold for detection was as high as 10 watts. In all cases, these limits to the powers that could be detected are quite modest – comparable to that of cell phones or citizen band radios.

    While no signals were found coming from Oumuamua, the types of observations reported by SETI Institute scientists may have utility in constraining the nature of any interstellar objects detected in the future, or even the small, well-known objects in our own Solar System. It has been long-hypothesized that some of the latter could be interstellar probes, and radio observations offer a way to address this imaginative, but by no means impossible, idea.

    The study is available on-line at:


  • ljk December 5, 2018, 18:52


    Radio SETI Observations of the Interstellar Object ‘Oumuamua

    G. R. Harp, Jon Richards, Peter Jenniskens, Seth Shostak, J. C. Tarter

    (Submitted on 28 Aug 2018)

    Motivated by the hypothesis that ‘Oumuamua could conceivably be an interstellar probe, we used the Allen Telescope Array to search for radio transmissions that would indicate a non-natural origin for this object.

    Observations were made at radio frequencies between 1-10 GHz using the Array’s correlator receiver with a channel bandwidth of 100 kHz. In frequency regions not corrupted by man-made interference, we find no signal flux with frequency-dependent lower limits of 0.01 Jy at 1 GHz and 0.1 Jy at 7 GHz. For a putative isotropic transmitter on the object, these limits correspond to transmitter powers of 30 mW and 300 mW, respectively.

    In frequency ranges that are heavily utilized for satellite communications, our sensitivity to weak signals is badly impinged, but we can still place an upper limit of 10 W for a transmitter on the asteroid.

    For comparison and validation should a transmitter be discovered, contemporaneous measurements were made on the solar system asteroids uz2017 and wc2017 with comparable sensitivities. Because they are closer to Earth, we place upper limits on transmitter power to be 0.1 and 0.001 times the limits for ‘Oumuamua. A concurrent set of observations over the same frequency range were made with a narrow-band (1 Hz) beamformer/spectrometer. Setting a 6.5 sigma threshold, the (frequency dependent) sensitivity limits on ‘Oumuamua were in the range 175 +/- 25 Jy into a 1 Hz bin.

    This rules out 1 Hz transmitters on ‘Oumuamua, 2017uz, and 2017wc to less than 500 mW, 50 mW, and 0.5 mW respectively over the frequency range from 1-10 GHz.

    Comments: 10 pages, 5 figures, submitted to Astrophysical Journal

    Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

    Cite as: arXiv:1808.09355 [astro-ph.EP]
    (or arXiv:1808.09355v1 [astro-ph.EP] for this version)

    Submission history

    From: Gerald Harp Ph.D. [view email]

    [v1] Tue, 28 Aug 2018 15:24:16 UTC (645 KB)


    • Harry R Ray December 6, 2018, 11:00

      A key quote from the UPDATED(12/4/18, NOT this one)version is that the authors state that `Oumuamua is “consistant with being an asteroud” based on their initial observations and their updated analysis. This is HUGE, because it ADDS to the growing amount of evidence that neither carbon dioxide was detected(Spitzer), nor was water ice or vapor(Green Bank). The focus right now should be on PROVING(at the six sigma or higher confidence level)that `Oumuamua is NOT a comet of any conceivable kind. Once this is done(and I am CONFIDENT that this will happen), there remains only two natural options. ONE: Somehow during its closest approach to the sun, `Oumuamua was converted into a natural magsail due to charging by the sun’s magnetic field, so that photons from the sun convert to electrons upon striking `Oumuamua’s surface and providing the force necessary to produce `Oumuamua’s non-gravitational acceleration, or; TWO: `Oumuamua is an only ~1mm thick NATURALLY FORMED object. Once “ONE” and “TWO” above, are the only two POSSIBLE natural solutions, we will see two things happen; ONE: More and more of the scientific community(and hopefully ALL of the SETI community)will start to believe the non-natural solution is a DISTINCT possibility, instead of JUST a REMOTE one, and; TWO: Calls for a mission to rendevous with `Oumuamua will become DEFINING!

Leave a Comment