Here’s a thought that puts a different spin on exoplanet studies. The speaker is Darryl Seligman (Cornell University):
“The comets and asteroids in the solar system have arguably taught us more about planet formation than what we’ve learned from the actual planets in the solar system. I think that the interstellar comets could arguably tell us more about extrasolar planets than the extrasolar planets we are trying to get measurements of today.”
Seligman’s comment plays into the growing interest in interstellar objects that drift into our Solar System like 1/I ‘Oumuamua and 2/I Borisov. These may be the initial members of what is actually a large class of debris from other stars that we are only now learning how to detect. Among the many things we have yet to refine in our understanding of ‘Oumuamua is its actual size. Projections of 115 by 111 by 19 meters are deduced from its brightness and the changes produced by its apparently tumbling motion. The interstellar interloper is too far from Earth and too small to resolve.
Image: This plot shows how the interstellar asteroid `Oumuamua varied in brightness during three days in October 2017. The large range of brightness — about a factor of ten (2.5 magnitudes) — is due to the very elongated shape of this unique object, which rotates every 7.3 hours. The different coloured dots represent measurements through different filters, covering the visible and near-infrared part of the spectrum. The dotted line shows the light curve expected if `Oumuamua were an ellipsoid with a 1:10 aspect ratio, the deviations from this line are probably due to irregularities in the object’s shape or surface albedo. Credit: ESO/K. Meech et al.
I mention this just to underline how difficult it is to make sense of ‘Oumuamua at present. Absent a fast mission to catch up with the object (and there are ideas out there, as we’ve discussed in these pages before), its dimensions will remain ambiguous. And what of the anomalous non-gravitational acceleration that astronomers noted in 2018? Seligman, who along with Gregory Laughlin has written about fast missions to ‘Oumuamua in a paper from that year, is also behind the conjecture that the object could be composed of molecular hydrogen ice. It’s no wonder, then, that his interest was piqued by Jennifer Bergner at UC-Berkeley, whose work involves chemical reactions on objects in space. And it has led to an alternative explanation for the anomalous acceleration of 1/I ‘Oumuamua, one he likes better than hydrogen ice.
Explanations for the acceleration have proliferated, many of them aimed at discrediting the concept that the object might be technological, a thought too radical for many scientists. But are ideas like hydrogen icebergs and shards of nitrogen credible in their own right? Bergner wasn’t satisfied with either pole of the controversy, and her initial work revealed that there was an explanation well documented in earlier research. Experiments beginning in the 1970s and continuing later showed what happens when ice is impacted by high-energy particles like cosmic rays. The process produces molecular hydrogen in quantity that remains trapped within the ice.
Warming up these pockets of molecular hydrogen would cause the outgassing of the H2, even if the gas were trapped tens of meters inside cometary ice. Says Bergner:
“For a comet several kilometers across, the outgassing would be from a really thin shell relative to the bulk of the object, so both compositionally and in terms of any acceleration, you wouldn’t necessarily expect that to be a detectable effect. But because ‘Oumuamua was so small, we think that it actually produced sufficient force to power this acceleration.”
That would be a helpful explanation if it can be made to fit. With the brightness of ‘Oumuamua changing periodically by a factor of 12 and varying asymmetrically, the object’s shape appeared to be elongated and its tumble was apparent. A ‘local’ comet leaving the Sun after perihelion is known to eject water and gas from its surface, producing the familiar gaseous coma and releasing dust. A dusty cometary tail forms, while a secondary tail of vapor, dust and possibly organic materials pushed by the momentum of solar photons can appear, this one pointing away from the Sun.
It was the absence of these processes that flagged ‘Oumuamua as unusual. There was no coma here, nor were outgassed molecules or dust observed, and as the authors note in their paper in Nature, solar energy hitting the object in its trajectory would not cause enough water or organic compounds to sublimate to account for the acceleration. Without a dusty coma, explaining ‘Oumuamua’s acceleration was a problem, which is why hydrogen icebergs and nitrogen shards emerged as hypotheses, for they could conceivably produce enough kick to supply the needed force.
Bergner’s search of the literature found earlier experiments where ice chilled to the temperatures of deep space is converted into molecular hydrogen by high-energy radiation. The release of that hydrogen by a heat source is sufficient, her work with Seligman confirmed, to produce a gas discharge that would affect ‘Oumuamua’s orbit. No dusty coma, then, is needed, and indeed, none is discharged by this process. Cometary ice is not sublimating but rearranging itself as H2 is released.
Seligman seems confident in the analysis:
“Jenny’s definitely right about the entrapped hydrogen. Nobody had thought of that before. Between discovering other dark comets in the solar system and Jenny’s awesome idea, I think it’s got to be correct. Water is the most abundant component of comets in the solar system and likely in extrasolar systems, as well. And if you put a water rich comet in the Oort cloud or eject it into the interstellar medium, you should get amorphous ice with pockets of H2.”
And in fact, working with Bergner, Seligman and colleagues have identified six other comets that lack an observable coma but demonstrate small non-gravitational accelerations. Usefully, one of these is comet 1998 KY26, which is targeted by Japan’s Hayabusa2 mission, the same mission that collected samples of the asteroid Ryugu. It was only in December of 2022 that 1998 KY26 was identified as a comet rather than an asteroid. Is hydrogen outgassing like this in fact common to deep space comets? The Rubin Observatory Legacy Survey of Space and Time (LSST), which will go into operation in 2025, may give us a notion of the distribution of such objects.
The paper is Bergner and Seligman, “Acceleration of 1I/‘Oumuamua from radiolytically produced H2 in H2O ice,” Nature 22 March 2023 (abstract).
If cometary water is broken down to release h2, then the remaining components will be oxygen-rich. This could make the h2O2 as we think occurs on Europa, but it may also modify carbon molecules and oxidize other reduced elements like nitrogen and sulfur. This may be detectable spectroscopically.
As peroxides occur on the surface of Europa, there should be a corresponding H2 emission. Whether that is detectable given the proximity of Jupiter, IDK.
Cosmic rays should have the same effect on Kuiper belt and Oort objects. Is there any evidence of H2 buildup on the Kuiper belt objects that could be detectable by New Horizons?
Yes, we should see supportive evidence from KB and Oort objects, good call.
My questions are….. OK, assume it accelerated due to volitiles out-gassing from proximity to Sol….
1. I would have assumed that out gassing occurred from multiple random areas on it’s surface (as it was rotating or tumbling) due to even heating. Ie, a non directional thrust.
2. Even if there was a directional thrust, where was this thrust as it approached the sun…. only seen as it accelerated away? Perhaps there was a “critical temperature” attained.
Out-gassing would be directly proportional to heat, it could have started on approach but had little impact on velocity. The most likely place to see acceleration is after the object has received the most heat. A critical temperature is a very likely prediction. The lack of decceleration is a much bigger problem for the solar sail hypothesis. Either the tumbling solar sail never faced the Sun on approach or, despite evidence, the sail opened when leaving the system.
Random multiple thrust vectors could cancel each other out leaving the strongest thrust vector dominant. For both the out-gassing and solar sail hypothesis this could be along a path away from the Sun. Imho, since a solar sail would have fewer randomly pointed thrust vectors, this could also be a bigger problem for the solar sail hypothesis.
Regarding net thrust direction. If the comet was broadly a spherical and tumbling I would agree this would seem to result in an approximately very low new thrust, possibly even zero.
But suppose it is relatively flat, and further that it isn’t tumbling, but rather rotating on its long axis so that its apparent shape looks like a long cylinder. The surface facing the sun remains heated for 1/2 the rotation, allowing the gases to heat and generate thrust. As that surface rotates so that it no longer faces the sun, the surface cools for another half of the rotation. Would that allow for a net thrust away from the sun?
Hi Paul
Reminds me of Drobyshevski’s speculations about build up of H2/O2 in exposed Ices that periodically causes the various ice moons to explode and produce showers of Jupiter Family Comets. Another possible energetic radiolytic product is hydrogen peroxide. That could well have supplied oxidative stress on bacteria that led to development of aerobic metabolism.
Cornell News Service article on this idea:
https://news.cornell.edu/stories/2023/03/first-known-interstellar-interloper-resembles-dark-comet
All this just adds up to we should have gotten a probe to Oumuamua when we had the chance. Let us not blow the next opportunity.
Avi Loeb’s analysis and conclusion remain unassailable. These alternative explanations border on lunacy because the astronomical profession is still infested by ET-denying astronomers.
Is `Oumuamua a Hydrogen-Water Iceberg?
“Sometimes, I feel like the kid in Hans-Christian Andersen folktale who suggested that “the emperor has no clothes”, while the “adults” watching the procession insisted that the emperor is dressed with fancy clothing. In my case, the emperor is `Oumuamua and the clothes are its invisible cometary tail.”
https://avi-loeb.medium.com/is-oumuamua-a-hydrogen-water-iceberg-a5d815f61c86
Both of our recent stellar interlopers have a kinematic behavior (orbits and velocities) perfectly consistent with protoplanetary disk debris ejected from other stellar systems long, long ago. The subsequent dynamic “acceleration” is unexplained, but neither startling nor unprecedented. Even if it cannot be completely explained, there is no compelling reason why it MUST be the result of an alien propulsion system.
In my opinion, a highly advanced technology capable of sending probes to other star systems could certainly come up with higher velocities and accelerations than our two visitors exhibit. And they would either make an attempt to noisily announce their presence OR would make every effort to conceal it (depending on their level of xenophobic paranoia).
Then again, maybe they ARE alien probes, disguised to look exactly like natural comets or planetoids, deliberately designed to act and behave like natural phenomena so they can sneak by us unnoticed..
Forget it, guys. They’re both rocks.
Loeb makes a couple of points about the acceleration, but given his calculations for the super dense meteor he wants to search for, I am suspicious of his calculations.
As for the shape of ‘Oumuamua, the disklike forms of the 2 lobes of Arrokoth make the probability higher of it being a natural rather than artificial object. To use his garden ability, a flat pebble is still a rock not a Frisbee.
Since our very primitive spacecraft skip across the earth’s atmosphere when returning from the moon like skipping a rock on water we may need to look a little closer as our military says:
Alien mothership lurking in our solar system could be watching us with tiny probes, Pentagon official suggests.
https://www.livescience.com/alien-mothership-lurking-in-our-solar-system-could-be-watching-us-with-tiny-probes-pentagon-official-suggests
But at least they are not sending any nuclear bombs our way like some of our neighbors on earth are threatening.
There is another severe threat that no one has mentioned in literature, the possibility of extragalactic objects impacting on earth. Galaxies like the large and small Magellanic Clouds and the mundane globular clusters pass through the milky way at speeds one to two million miles an hour depending on the angle of entry. Lets say there is a rogue planet or large comet left over from one of these previous encounters, we would have only 93 to only 47 minutes if it came from behind the sun before impact at 1 to 2 million miles an hour! Has anyone or group looked into this possibility??? Even small objects coming from outside the galaxy or orbiting outside the plane of the milky way would hit the earths atmosphere like hitting a brick wall. A very brief blast would be all that is seen because of the speed, with no trails like seen by normal meteors entering the earth’s atmosphere at 1/10 to 1/20 of the speed.
Interesting and very deadly!
An excellent point, One that never occurred to me.
Space debris from stars floating in the general galactic drift, the LSR, would strike the earth at velocities of several tens of km/sec. Objects from the galactic halo, like ‘high-velocity stars’, while still orbiting the galactic nucleus, have potential speeds relative to disk stars (and Earth) an order of magnitude higher.
But a meteor or planetoid that originated in another galaxy would be approaching us at the ‘peculiar’ velocity of that galaxy (the typical velocity of galaxies in a gravitationally bound cluster, unaffected by general cosmological expansion). For example, the blue shift of the Andromeda galaxy is about 300 km/sec, although most of that is due to our Sun’s own orbital velocity around the Milky Way’s center. Andromeda’s velocity relative to our own galaxy is about 130 km/sec.
I really don’t know the velocity distribution of other galaxies in the Local Group. Some of them might be clipping along at pretty high velocities, relative to Earth.
E = 1/2 Mv^2.
HRC thanks for the comment and there is more to the story;
12 Stellar Streams Within Our Galactic Halo: The Milky Way’s Feeding Habits Shine a Light on Dark Matter.
https://scitechdaily.com/12-stellar-streams-within-our-galactic-halo-the-milky-ways-feeding-habits-shine-a-light-on-dark-matter/
This means there is a lot of material flying into the milky way and much of this material may be in retrograde orbit around the milky way!
“Many of the Milky Way’s globular clusters have a retrograde orbit (meaning that they revolve around the galaxy in the reverse of the direction the galaxy is rotating), including the most massive, Omega Centauri. Its retrograde orbit suggests it may be a remnant of a dwarf galaxy captured by the Milky Way.”
https://en.wikipedia.org/wiki/Globular_cluster
Last paragraph of section on Formation.
Retrograde would indicate speed of -410 km/sec to galactic arms at +410 km/sec equal 820 km/sec. That figures close to 3 million kilometers an hour or close to 2 million miles an hour!
Many of these objects are stripted of their gases but how much materiale is left in the form of comets and asteroids is a good question. We have plenty of examples of impact craters throughout the solar system but how can we tell the difference between a object that impacted at ten to twenty times the speed of comets and asteroids in our solar system?
Would such things as sand size meteors traveling at these speeds even leave a trail or just flash out in a microsecond. This could be a new phenomenon that would be relatively easy to capture with high speed astro cameras.
Has anyone even looked for objects traveling at these speeds through our solar system, an asteroid trail that would be mistaken for an earth orbiting satellite because of its speed???
The only way that larger objects could be defended against is with a laser array because detection would be only minutes before impact.
Sounds like something out of science fiction but we are just beginning to understand the dynamics, maybe some of the pre satellite photo surveys image something like this but mistaken them for meteors?
Back in the olden days, I was taught about ‘head-on meteors’, meteoroids that approached the observer directly, leaving no track across the observer’s line of sight. I’ve seen a few myself!
It is possible that some of these were bodies traveling so fast that their encounter with our atmosphere, (regardless of their direction of travel) led to immediate destruction, not a spectacular meteor trail. If any of these objects survived relatively intact when they hit the ground, the resulting crater would be much larger than one created by an identical meteoroid traveling at more moderate speeds. (Kinetic energy varies linearly with mass but as the square of the velocity.)
Still, I wouldn’t worry about it. The Earth may have been hit many times in its history by these hyperfast extragalactic bolides, but it has survived. Their impact is probably indistinguishable from one by a slower, but correspondingly much more massive object, Detecting these bodies would probably be no different that detecting more ordinary interlopers, although it is only recently that we have developed the technology to see them! As for defending ourselves against them, that would be next to impossible even if we could detect them.
As an astronomy student, I spent many hours staring through microscopes at photographic plates of time exposures (for astrometric research). The tiny streaks of asteroids littered these images, but it was impossible to develop orbits for them since they were only observed once, and often on archival images taken many decades earlier. I never once saw a meteor trail, though. They would have been easily identifiable because the length of the trail (across the entire plate) would be much longer than the trail left by an asteroid (formed only during the time of the exposure)..
I just wondering if something like the Rubin observatory and any other ground based deep space observatories could tell the distance and orbit of any such object. Maybe AI could discern the difference.
My apology, the distance of an object passing near the sun to reach an impact on earth is 93 million miles and at 2 million miles an hour it would take 2 days. These objects could approach earth from all angles since they are not in the plane of the solar system or the Milky Way’s galactic plane.
Planetary Defense Warning Stations
https://avi-loeb.medium.com/planetary-defense-warning-stations-c0f1afb73d7a
The Lagrange points L4 and L5 have long term stability for any earth observation platforms. The main problem is that these areas move along the ecliptic plane as the earth orbits the sun. They would be a nearby area to search for any type of unusual images in the deep sky archives.
IMPLICATIONS OF EVAPORATIVE COOLING BY H2 FOR 1I/‘OUMUAMUA.
ABSTRACT
“The first interstellar object observed in our solar system, 1I/‘Oumuamua, exhibited several peculiar properties, including extreme elongation and non-gravitational acceleration. Bergner & Seligman (2023) proposed that evaporation of trapped H2 created by cosmic rays (CRs) can explain the non-gravitational acceleration. However, their calculation of surface temperature ignored the crucial cooling effect of evaporating H2. By taking into account the cooling by H2 evaporation, we show that the surface temperature of H2-water ice is lower than the temperature obtained by Bergner &
Seligman (2023) by a factor of 9. As a result, the thermal speed of outgassing H2 is decreased by a factor of 3, which requires that all H2 from water ice is dissociate by CRs in the interstellar medium,
making the model untenable as an explanation for the properties of 1I/‘Oumuamua. Moreover, the lower surface temperature also influences the thermal annealing of water ice, a key process that is
appealed by Bergner & Seligman (2023) to release H2.”
https://lweb.cfa.harvard.edu/~loeb/Hoang_Loeb_23.pdf
It’s a rock.
Yes but it is a Alien rock.
How different might it be? It looks like something that broke off the Andes or such and slid down a mountainside. Maybe collision debris. I can’t see it as a super advanced starship.
True, we oughta have something ready to get samples next time something like that comes by.
It is certainly an intriguing and interesting proposal, it appears far more credible than many other proposals to explain the non-gravitational acceleration observed.
In theory, such outgasing should be observable on bodies in the outer solar system where conditions exist that replicate those on interstellar objects.
We know that many of the Kuiper belt objects, and likely those in the scattered disk, which are within range of current instruments, contain H2O as a component of their surface material, similar effects should take place – although we would not see any acceleration, the outgassing of H2 and N2, as well as detections of H2O2 and other peroxides should be possible.
The detections would lend support to the idea of this theory.
I feel we should question whether it was a discarded shell casing, ejected at high velocity, from a planetary system-sized mecha, as depicted in Gurren Lagann. The unusual aspect ratio is more plausible then.
I wonder if the eccentricity of the aspect ratio could be less extreme if we assumed the material had strong specular reflections?
The problem is with making such an extraordinary leap of faith, you need extraordinary evidence to support it – or at least for every possible natural solution to have been ruled out.
Now I am not saying it could not have been technology from a distant home, but when you weigh up the data, we simply do not know and cannot prove but the law of averages dictates that it is 99.9999999% more likely to be natural, if somewhat unusual, that is is artificial.
For all we know, the object could be a section of a neutron star that sluffed off when it’s surface cracked – extremely unlikely given what we do know – but I would posit that it is fundamentally more credible as an explanation that it being alien technology – and I for one do not believe it is part of the neutron star.
How many other interstellar visitors have their own song…
https://manualmusic.bandcamp.com/album/oumuamua-album
Remember when Oumuamua was a fractal dust aggregate? Anything but an alien vessel.
https://arxiv.org/abs/1910.07135
1998 Ky26 isn’t an asteroid? 1998 KY26 is a “comet” 30 meters in diameter (maybe I should say mini-comet) with a rotation period of 10.7 minutes (that’s one tough “dirty snowball”) and an orbit that rather resembles a Hohmann trajectory between Earth and Mars (not what I would expect from a short period comet)?
Well, okay. Is there a reference I could access?
Re 1998 KY26, let me see what I can learn from the paper’s authors. I’d like to know more about this object as well, as its cometary status seems unusual.
And here we go, from Dr. Seligman:
https://iopscience.iop.org/article/10.3847/PSJ/acb697
https://arxiv.org/abs/2212.08135
Paul:
Thank you.
First of all, thankyou to Paul for this amazing site /blog /resource where you can actually engage in serious discussion with an open mind, but with a scientific base and on a level that a rookie like me can at least begin to understand. Its one of its kind on the internet!
Now regarding Oumuamua;
Is his not becoming ridiculous? The comet /asteroid /alien probe was speeding up as it left the solar system. If it had been releasing hydrogen gas (while spinning out of control) there would be no straight angle of directed thrust, thus it would have not increased its speed in the way it did. Why is everyone so intent on accepting anything to be able to reject the possibility of something unknown or alien? No, Im no scientist, but I am not scared of the unknown, I find it exciting. Im not saying that it was anything “alien” in that sense, but all the explanations feels so.. I dont know – fake and desperate? (sorry for my novice level of english)
Thank you for the kind words, Daniel. Much appreciated! Delighted to have you on the site.
No one posting on this website is hostile to the idea of Extra Terrestrial Intelligence. On the contrary, that’s why we come here. We really want to believe. But we are also scientists (or at least, scientific!) and conservative skepticism is both natural and necessary for our speculations to have any value. We cannot let our desires influence our conclusions.
As for your point of the acceleration vector for Oumuamua, a uniformly tumbling rock with a geyser on its surface would indeed have a wildly flailing thrust. But the velocity vector would be the INTEGRATED result of that varying acceleration, and it would be in only one direction. In other words, even if the acceleration varies, the summation of those accelerations is a constant, so the direction of the velocity vector does not change, only its magnitude. All the observations really suggest is that the object was speeding up as it left the solar system, that the summation of the forces acting on it were causing it to speed up relative to the sun.
Of course, we don’t know for certain that is all that is happening, but it is not an unreasonable assumption and it explains the observations adequately. For the time being, it is our best hypothesis.
And your English is excellent. No doubt it is much better than my command of your native language.
Spin is often far from simple. There can be more than one spin axis. As a result, any “geyser” can flail around quite a lot less, or more, than one might expect. For example, it could trace out a small circle that itself rotates on a different axis.
This phenomenon is at the heart of a common magic trick. It is possible to flip a fair coin and have it land heads or tails, as you wish. I’ve practiced this trick and it works quite reliably. Onlookers have no idea how the trick is done; they just see a spinning coin arcing through the air and assume the outcome is unpredictable.
Could it be a pumice rubble pile degassing, pumice can have densities of around 0.25g/cm^3 and lower densities for been a rubble pile, it has plenty of room to store gasses.
If we look at the pores of pumice they would offer a somewhat efficient motor nozzle with a connection to a reservoir of stored gases beneath.
https://static3.bigstockphoto.com/4/6/1/large1500/164818958.jpg
This could shape up as Clarkian-style scifi story….
The year is 2135. Earth has increased its monitoring of small celestial bodies with many space-based telescopes across the solar system. There have been hundreds of identified interstellar intruders, but all have looked like Borisev 2. ‘Oumuamua has remained a unique object the likes of which have never been seen again. It is decided that finding the object is imperative and the comet-chaser Laelaps is dispatched to hunt down ‘Oumuamua to investigate it. Boosted to 1% of lightspeed by a laser sail, the craft discarded its sail keeping its fusion engine ready to maneuver towards its “prey”.
In related news, Loeb is off to find that super-dense meteor off the coast of Papua New Guinea.
Harvard physicist plans expedition to find ‘alien artefact’ that fell from space
There are many trillions of small interstellar objects travelling the Milky Way. The claim that other space space faring people also inhabit the galaxy is not an extraordinary claim. Space faring people, as a category, become less extraordinary as the population increases. However, the odds that the first small interstellar traveler we detect is artificial is mid-boglingly small and therefore an extraordinary claim.
Isn’t Loebs’s claim that the shape implies a solar sail of some type? If so, it also must overcome the tumbling problem. The problem can be overcome, the sail would provide the most acceleration whenever most of the reflective surface faced the sun. A pancake shaped object made of hydrogen or nitrogen will experience the greatest out-gassing when it presents the greatest surface area to sun. Same applies to the model presented here for H2 whether the the H2 conversion is widely distributed through the object or concentrated.
The claim that scientists aren’t willing to entertain the space-faring people hypothesis is simply wrong.
The main problem I have with the alien hypothesis here is that Oumuamua is a poor excuse for a starship. It started at “local standard of rest”, galactic flotsam traceable to no nearby star. In over a month, it managed to change velocity by 17 m/s (= 38 mph = 0.000000057 c), then headed out nowhere in particular. Why would the aliens have left a spaceship floating in interstellar space for geological time frames, aimed all that time to pass by the Sun in the blink of an eye and then go away, with a trifling course correction? Why are they doing a course correction while they leave it spinning aimlessly? If they are hiding their power, shouldn’t they have put off all course correction until they were further away, and if not, shouldn’t they have steered it into an orbit?
I have seen shards of rock explode:
https://m.youtube.com/watch?v=JZ4GVc88jTU
https://m.youtube.com/watch?v=-v-II1FPFSU
Maybe a shard of something like half dome that calved a bit on the way out?
Avi Loeb discusses the paper with Brian Keating