I’ve used the discovery of ‘Oumuamua as a learning opportunity. I knew nothing about the Local Standard of Rest (LSR) when the analysis of the object began, but soon learned that it measured the mean motion of interstellar materials in the Milky Way near the Sun. The Sun moves clockwise as viewed from galactic north, with an orbital speed that has been measured, through interferometric techniques, at 255.2 kilometers per second, give or take 5.1 km/s. Invoking the LSR in this connection calls for a quote from Eric Mamajek (JPL/Caltech) in his paper “Kinematics of the Interstellar Vagabond 1I/’Oumuamua (A/2017 U1)” (abstract here):
‘Oumuamua’s velocity is within 5 km/s of the median Galactic velocity of the stars in the solar neighborhood (<25 pc), and within 2 km/s of the mean velocity of the local M dwarfs. Its velocity appears to be statistically “too” typical for a body whose velocity was drawn from the Galactic velocity distribution of the local stars (i.e. less than 1 in 500 field stars in the solar neighborhood would have a velocity so close to the median UVW velocity). In the Local Standard of Rest frame (circular Galactic motion), ‘Oumuamua is remarkable for showing both negligible radial (U) and vertical (W) motion, while having a slightly sub-Keplerian circular velocity (V; by ~11 km/s). These calculations strengthen the interpretation that A/2017 U1 has a distant extrasolar origin, but not among the very nearest stars. Any formation mechanism for this interstellar asteroid should account for the coincidence of ‘Oumuamua’s velocity being so close to the LSR.
Below is what ‘Oumuamua really looks like. As opposed to the artists’ conceptions we’ve all seen, each of which makes its own set of assumptions based on current studies, this is what we have on this object visually. As you can see, it isn’t much to work with.
Image: This very deep combined image shows the interstellar object ‘Oumuamua at the center of the image. It is surrounded by the trails of faint stars that are smeared as the telescopes tracked the moving object. Credit: ESO/K. Meech et al.
Harvard’s Avi Loeb has likewise noted that an interstellar object should have inherited the motion of its birth star, and thus would not have been likely to be found at the Local Standard of Rest. Now, in a new piece for Scientific American called Was the Interstellar Object ‘Oumuamua a Nitrogen Iceberg?, Loeb references the paper by Alan Jackson and Steven Desch that argues for ‘Oumuamua being a nitrogen ‘shard’ from an outer system object, the equivalent of Pluto in our own Solar System. We looked at this paper on Friday.
Loeb points out that a nitrogen iceberg would be an oddity given that we’ve never seen one of these among objects found in our own Oort Cloud, that agglomeration of perhaps trillions of comets that extends halfway to the Alpha Centauri triple system. Yet if the first interstellar object detected turns out to be made of nitrogen, the implication is that objects like this are common, and perhaps they are in other stellar systems. Fortunately, this is something we’ll be able to study in the near future as observatories like the Rubin LSST become available. The catalog of interstellar objects should grow quickly and the likelihood of nitrogen ice can be examined.
It always helps to know what to look for, but then, ‘Oumuamua has surprised us on several fronts. Loeb also points out that about a tenth of the object’s mass would need to have evaporated to explain its deviation from the expected path as it left the Solar System (Desch and Jackson cite a much higher fraction of the object’s mass). This point continues to draw attention because post-perihelion evaporation should have caused jitter on the departing object, a change to the rate at which it was tumbling. As far as I can see, the issue of ‘Oumuamua’s behavior is still problematic.
Meanwhile, the Oort itself retains its fascination. A cloud of cometary material reaching out to what may well be a similar Oort Cloud at Alpha Centauri (its existence is not proven, of course) would provide a far future civilization a way to move slowly outward, exploiting resources along the way in a multi-generational wave that took advantage of the ubiquity of such objects. For today’s purposes, you would think we might be able to exploit exo-Oort Clouds, if they are there, to work backward along the route of ‘Oumuamua to find the star from which it came, but Loeb points out that there would simply be too many Oort analogs along the line of sight to allow any firm identification.
So we move forward in the ‘Oumuamua discussion, with nitrogen ice now in the mix, with its own caveats, as a potential explanation. As we work out the implications, Loeb also notes that the population of interstellar objects may exceed anything we’ve previously estimated:
…most objects within the Oort cloud volume may not be bound to the sun. In another paper with Amir [Siraj], we showed that the recent discovery of the interstellar comet 2I/Borisov, which most likely originated from an Oort cloud around another star, implies that interstellar objects may outnumber solar system objects within our own Oort cloud. In other words, the Oort cloud objects bound to the sun are swimming in an ocean of background interstellar objects that come and go. Moreover, the discovery of 2I/Borisov implies that about a percent of all the carbon and oxygen in the Milky Way galaxy may be locked in interstellar objects.
The opportunity presented by such a wealth of interstellar materials ranging from dust particles to free-floating planets is immense, and if there is a growth engine embedded within the astronomical community for the next decade or so, it’s surely here, as we begin identifying more and more objects born around stars other than our own. Who knew even a few years ago that we might be able to take advantage of so widespread a phenomenon to study materials from other stellar systems without the need to put our own probes around their stars?
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I see his point, we may want to start looking for much smaller objects, about 50% of the meteorites from interstellar space should be older then the solar system. Just how fast would they be entering the earth’s atmosphere if they are at Local Standard of Rest (LSR)? There should be an easy way to identify these objects from trajectory and speed analysis of their trails before impact. CubeSats and on the ISS there could be set up directionally in space, aerogel to capture small particles coming from the direction of LSR.
In that piece in Sci Am, Loeb says that “Generally, nitrogen is produced together with carbon through the carbon-nitrogen-oxygen, or CNO, cycle in stellar interiors.” This is not true. The CNO cycle does not produce C, N or O, but He from the fusion of H in relatively heavy main sequence stars, in a chain of reactions where they play the role of “catallitsts”. It surprised me that an astrophysicist could say something like that. I am a physicist, not particularly trained in astrophysics.
I am not sure how much this affects his arguments. But the mother object of Oumauma may well had C together with N in its composition, yet a pure N shard could form. We know as much, because we have seen this in Pluto.
Nice piece, as always, Paul.
That’s absolutely right, C and N are catalysts in the CNO cycle mode of hydrogen fusion. C and N are produced in the triple alpha process. I’m surprised by this slip, too. Not that any of this matters for the composition of a planetary ice.
I also want to point out that young stars move slowly relative to the LSR. All that is needed to explain ‘Oumuamua’s speed is that it cane from a young (< 2 Gyr) star. Nothing weirder than that.
And the most likely period for impacts is during a stellar system’s youth. Also, in the cold, outermost reaches of systems it takes much less energy to propel ejecta clear out of the system.
Objects collect in lagrange points (most stably L4 and L5) in the solar system, so it it possible there are complex temporary equivalents between the sun and the nearest stars? Could there be a higher density region of objects temporarily trapped where the gravitational influence between Alpha Centauri and the Sun cancels out?
With frozen N₂ as a carrier, cowplex organic structures could be preserved almost indefititely, as a possible method for panspermia.
While I like your concept of capturing interstellar material, I think another method is needed. 2I/Borisov was interstellar but not from the LSR. grains of different sizes will penetrate aerogel at different depths that are a function of both mass and velocity.
What we need is a way to create a “Maxwell’s Demon” to accept grains with a velocity above a threshold and reject those below that threshold. Directionality might be irrelevant, although possibly informative. The “probes on standby” to rendezvous with larger bodies, while far more costly, would meet the needed criteria for large bodies.
he capture and exposure experiments in the Tanpopo mission were designed to confirm the hypothesis that extraterrestrial organic compounds played important roles in the generation of the first terrestrial life, as well as examination of the hypothesis of panspermia. If the Tanpopo mission can detect microbes at the higher altitude of low Earth orbit (400 km), it will support the possible interplanetary migration of terrestrial life. The mission was named after the plant dandelion (Tanpopo) because the plant’s seeds evoke the image of seeds of lifeforms spreading out through space.
Japan project that could have samples from outside the solar system so interstellar panspermia!
But note that the device is sweeping up everything and not trying to select interstellar material by velocity. It must use analytic tools to try to determine if any of the material is interstellar rather than local.
Quoting from Paul’s essay on Oumuamua:
“Below is what ‘Oumuamua really looks like. As opposed to the artists’ conceptions we’ve all seen, each of which makes its own set of assumptions based on current studies, this is what we have on this object visually. As you can see, it isn’t much to work with.”
Yes one of my big pet peeves about Oumuamua are the artist’s rendering of the object. Their imaginings have probably done more to influence the debate than just about anything else by volume, and I include otherwise professionals in this category, too.
I know these artists were “just doing their job” and probably happy to get a paycheck for their talent, or so I presume. However, I have seen way too many comments from the public every time an article about Oumuamua pops up accompanied by a representative artwork that shows they seldom read the actual piece or are unaware of the evidence that our visitor looks far more like a thin, flat disk than a giant turd, and no I won’t pardon the expression here.
Why is this a big deal? Because it will and has entered into the debate whether or not to send a probe after Oumuamua. If they think it is just another rock – which it is not, even if it is an otherwise natural celestial body – then those with the purse strings won’t bother to loosen them for a mission. However, had Oumuamua been represented as a disk from the start, I bet we would either have had some kind of probe already on its way or a mission being put together, rather than just a white paper or two and Oh gee whiz, well we’ll get ’em next time.
I hate thinking what we may have missed, alien artifact or not. It is our first known interstellar visitor, that should be enough to go for it. Humanity has certainly spent far more money, resources, and time on far less worthy efforts. This is another bungling on a galactic level so far as I am concerned.
But don’t we have the reverse problem with exo-planets. Many are depicted as Earth-like, with continents, water, clouds, etc. We don’t know that. They may be desiccated like Venus. The attractiveness of finding an Earth II is used to support funding of more searches. This seems to be recapitulating the Mars story when it was thought to have plants where the surface was “green” and until the 1960s, possibly having canals that implied intelligent life. Wouldn’t such a world be more interesting to explore than the real Mars and therefore stimulate funding for interplanetary travel?
In some ways it always gets me that we are searching alien worlds not necessarily for places different from ours but instead almost identical.
Based on what I have seen, this is no doubt in part to fulfill a near-fantasy that one day we can go there to settle – and although these worlds are supposed to be Earth-like, they will somehow not contain beings like us, or just higher intelligence species in general.
And of course this does not take into account that the descendants from Earth who might end up being able to do this won’t be much like us at all. Perhaps even enough where a planet like Sol 3 would actually be less beneficial to their staying.
Stanislaw Lem was right again. from Solaris:
“We have no need of other worlds. We need mirrors. We don’t know what to do with other worlds. A single world, our own, suffices us; but we can’t accept it for what it is.”
“We take off into the cosmos, ready for anything: for solitude, for hardship, for exhaustion, death. Modesty forbids us to say so, but there are times when we think pretty well of ourselves. And yet, if we examine it more closely, our enthusiasm turns out to be all a sham. We don’t want to conquer the cosmos, we simply want to extend the boundaries of Earth to the frontiers of the cosmos. For us, such and such a planet is as arid as the Sahara, another as frozen as the North Pole, yet another as lush as the Amazon basin. We are humanitarian and chivalrous; we don’t want to enslave other races, we simply want to bequeath them our values and take over their heritage in exchange. We think of ourselves as the Knights of the Holy Contact. This is another lie. We are only seeking Man. We have no need of other worlds. A single world, our own, suffices us; but we can’t accept it for what it is. We are searching for an ideal image of our own world: we go in quest of a planet, a civilization superior to our own but developed on the basis of a prototype of our primeval past. At the same time, there is something inside us which we don’t like to face up to, from which we try to protect ourselves, but which nevertheless remains, since we don’t leave Earth in a state of primal innocence. We arrive here as we are in reality, and when the page is turned and that reality is revealed to us – that part of our reality which we would prefer to pass over in silence – then we don’t like it anymore.”
Once again, not searching for a new and quite different alien world, but another Earth…
RE: “Loeb also points out that about a tenth of the object’s mass would need to have evaporated to explain its deviation from the expected path as it left the Solar System (Desch and Jackson cite a much higher fraction of the object’s mass).”
These are estimates of different things. Avi was estimating the mass loss _during our period of observation_, while Desch and Jackson estimate that the proto-1I lost 90%+ of its mass while it was going through perihelion (i.e., _before_ we found it).
The latter estimate at the center of the concerns I have with this proposal.
– N2 ice has a triple point of 63 K. 1I had a perihelion of 0.255 AU and was within 1 AU of the Sun for 2 months (60 days) and 0,5 AU of the Sun for 24 days. That’s a long time to keep a cryogenic ice hot. Desch and Jackson estimate 1I lost 90%+ of its mass in this process. I suspect it would be a good deal more and would want a more detailed analysis to look into that.
– But, at the same time, 1I did not break up in its perihelion passage. That seems very convenient for a shard of ice that was the result (in this theory) of a collision, and so presumably had cracks. Comets that lose a lot of mass tend to break up, but 1I didn’t.
– But, at the same time, you had a 200 meter comet (the original 1I) almost completely sublimate near the Sun, and neither STEREO or SOHO observed it.
– And, finally, on Pluto the N2 ice seems to have CO mixed with it. 1I couldn’t have had any of that, or Spitzer would have seen the CO.
Whether it’s hydrogen or nitrogen, the gain and loss of mass-equivalent light may well be what propels an object like this. That would also explain the reflections that are seen.
Was it “Rendezvous with Rama” that described using a nuclear explosion to produce a blast of super-power radio waves that generated reflections from Oort objects as the sphere of radio waves expanded? The reflected waves were measured to determine the location and approximate size of the various objects; presumably numbering in the tens to hundreds of thousands. A clever idea by Arthur C. Clarke but the practicality may be questionable.
No that was in Clarke’s novel The Hammer of God, published in 1993.
The original short story from 1992 that the novel is based on here:
None other than the Father of the Soviet Hydrogen Bomb, Andrei Sakharov, proposed in 1971 using nuclear bombs set off in deep space to get the attention of ETI:
Such an extremely powerful, single-pulse radar system–called Excalibur–was mentioned in one of the Rama series of novels (the second one, I think). It utilized a high-yield, enhanced-EMP (electromagnetic pulse) thermonuclear bomb, detonated on or above the center of the lunar farside (to protect Earth’s electronics from being fried by the EMP). Such a device might well actually work, although it might have to function in bistatic mode, with one or more fixed receivers on Earth, far from the bomb (a receiver located on the Moon, not far from “ground zero,” would have to be grounded and/or RF-shielded *VERY* well, or else the transmission pulse would fry it), and:
I wouldn’t be surprised if the Excalibur radar system also appeared in Clarke’s novel “The Hammer of God,” as he considered some fictional–but possible–future inventions and mega-structures to be almost characters in their own right, which appeared in multiple works, although sometimes as “extras.” His projected Gibraltar bridge is mentioned in at least two of his novels, “The Fountains of Paradise” and–melting as the Earth dies (due to a solar “mini-nova”-type event, based on the actual, apparent “deficit” of solar neutrinos observed in the 1970s and 1980s [and his imagined solar reaction to it])–in “The Songs of Distant Earth.” Also:
Many people don’t like the subsequent novels (after “Rendezvous with Rama”), which Arthur C. Clarke and Gentry Lee wrote in collaboration; they certainly are an abrupt change in “feel” from the original one, which Clarke wrote by himself, and that change may put them off. But taken on their own merits, without comparison to the style of the original, I found them enjoyable, and the alien races the human crews met imaginatively conceived.
Not sure what to make of the galactic standard of rest. Aren’t distant stars just as unlikely as close ones to be travelling at very close to the mean galactic vector? And if ‘Oumuamua was ripped out of a system due to a close call with a passing star (or indeed with a giant planet in its own system), why would we still expect it to be travelling with a velocity that matches its home system?
Yep, still wondering how it picked up that smooth acceleration while tumbling.
Thanks for the good questions and for deciphering the 10% vs. 90% thing.
N2 actually sublimates at 25 K in vacuum. But that same sublimation leads to evaporative cooling (if you’ve ever shivered with cold getting out of a pool on a 115 F day in Phoenix you know how this works) that kept it at 45-50K. We calculate (not estimate) the coupled temperature and mass loss in a careful detailed analysis in paper 1.
Comets are loosely bound aggregations of small things (e.g., 67P) and can break up whenthey enter the Sun’s Roche limit. This object never heated above 50K and never got nearer to the Sun than 0.25 au, so no reason to break up. Even if it were to break up in SOHO’s field of view, all there would be to see is N2, invisible at optical wavelengths.
Finally, Pluto’s ices are 0.1% CO, and at these levels would have been below Spitzer’s detection limits, as described also in paper 1.
And thank you, Dr. Desch, for joining in the comments here. Much appreciated!
Thank you Steve Desch, yes the latent heat from sublimation do indeed refrigerate the remaining material. That’s a physic lesson from primary school, and also a thanks for the comment on nuclear processes which is another basic thing knowing how the Sun work.
I was about to say that the idea that possible cracks in Oumuamua would have forced it to break up was incorrect, as many comets indeed survive many passages to the Sun. But it’s better to have an expert in the field say so than me who is just a mere biology researcher.
Anyway, and said to anyone who might have an interest, I go back to lurking as spring has arrived in the south we’ll start working towards the north doing work planned also for 2020 – which was cancelled due to COVID. So I go back to lurking for this forum now.
Have a nice spring everyone! =)
Assume for the sake of argument that Oumuamua was an artifact of some other civilization. And assume that its unusual acceleration was some kind of controlled maneuver. Has anyone tried to determine what that maneuver actually did? Did it shift the object onto a course for some nearby star? Or avoid a planetary encounter?
I ask because a maneuver with a purpose would be much stronger proof of O. being an artifact than a random pointless acceleration.
One thing to wonder is, was Earth its intended target? We automatically assume an alien vessel in our Sol system would want to visit us, even if discreetly. However, there are other worlds here much larger and other containing intriguing elements that we may be only vaguely aware about which might better capture the imagination and goals of an ETI, especially if they are Artilects.
If an advanced ETI is anything like a human scientist studying animals in the wild, they will do their best not to interfere with the natives so as to keep them in a state of natural behavior. Or perhaps they assume since we had not noticed any interstellar visitors before 2017 that a flyby would not generate any disruptions from the inhabitants of Sol 3. Or maybe they just could not care less how we react to them.
Maybe someone can explain this to me.
I can see how a geyser-like vent outgassing sublimated gases could provide thrust; but I thought the object was also tumbling as it traveled through space. The orbit should not be constrained to one plane. Has this actually been observed?
An “exhaust” rotating with respect to the orbital axis should result in a periodically varying acceleration vector.
Well that’s two of us. Anybody have an answer?
Why should we expect that other solar systems have an Oort cloud?
Curious- can we explain the formation of dense Oort cloud objects from gas and dust disbursed over such huge areas?
Even MORE interesting, what mechanism imparts sufficient radial velocity / angular momentum to put them in a circular orbit, instead of a typical cometary orbit?
Example- according to the generally accepted Nice Model the motions of the gas giants Jupiter and Saturn kicked out small planetesimals that formed near the ice-line, which were scattered into the Kuiper or Oort cloud.
However, while those interactions would one impart outward acceleration, it would seem that it cannot impart the radial velocity needed to keep such things in orbit- rather like a sounding-rocket that flies straight UP, stops, then drops straight DOWN.
In contrast, to put a satellite in orbit, you have to put a huge amount of RADIAL velocity so that it has enough speed to stay in orbit. While gravity assists from gas-giant planets and ice-giant planets can accelerate objects out into the Oort cloud, they don’t seem to be able to impart the necessary radial velocity to produce a circular orbit and place such objects in an Oort cloud orbit.
Curious to hear from others on this!
Professor Avi Loeb, Harvard Astrophysicist
by: Frank Buckley
Posted: Mar 24, 2021 / 07:15 AM PDT / Updated: Mar 24, 2021 / 07:15 AM PDT
Professor Avi Loeb is the Frank B. Baird, Jr., Professor of Science at Harvard University. He is the former chair of the Astronomy Department at Harvard (2011-2020). Professor Loeb is the founding director of Harvard’s Black Hole Initiative and director of the Institute for Theory and Computation within the Harvard Smithsonian Center for Astrophysics.
The professor also chairs the advisory committee for the $100 million research and engineering program, Breakthrough Starshot Initiative, which aims to demonstrate a proof of concept for a new technology enabling space flight at 20% the speed of light for a flyby mission to Alpha Centauri. Professor Loeb’s new book is “Extraterrestrial: The First Sign of Intelligent Life Beyond Earth.”
During this podcast, Professor Loeb discusses his theory as outlined in his book that an interstellar object dubbed Oumuamua that hurtled through our solar system in 2017 was possibly created by alien intelligence.
The ‘Oumuamua Encounter: How Modern Cosmology Handled
Its First Black Swan
Department of Finance, The University of Melbourne, Parkville, VIC 3010, Australia;
firstname.lastname@example.org; Tel.: +61-38-344-3696
The first macroscopic object observed to have come from outside the solar system slipped back out of sight in early 2018. 1I/2017 U1 ‘Oumuamua offered a unique opportunity to test understanding of gravity, planetary formation and galactic structure against a true outlier, and astronomical teams from around the globe rushed to study it. Observations lasted several months and generated a tsunami of scientific (and popular) literature.
The brief window available to study ‘Oumuamua created crisis-like conditions, and this paper makes a comparative study of techniques used by cosmologists against those used by financial economists in qualitatively similar situations where data conflict with the current paradigm.
Analyses of ‘Oumuamua were marked by adherence to existing paradigms and techniques and by confidence in results from self and others. Some, though, over-reached by turning uncertain findings into graphic, detailed depictions of ‘Oumuamua and making unsubstantiated suggestions, including that it was an alien investigator.
Using a specific instance to test cosmology’s research strategy against approaches used by economics researchers in comparable circumstances is an example of reverse econophysics that highlights the benefits of an extra-disciplinary lens.
The full text here:
The PDF version here:
If ‘Oumuamua lost 90% of its mass, its initial brightness must have been greater than that observed when discovered. Shouldn’t it have been detected before its perihelion or earlier than October 19, 2017?
I would like to think and hope that astronomers checked for pre-discovery images of Oumuamua in their records. Does anyone know?
I did find something on the second one, Borisov:
For ‘Oumuamua, there has of course been research into his presence on images prior to discovery. Wikipedia says: “Weryk – the
discoverer – then searched the Pan-STARRS image archive and
noticed that the object was also featured on images taken at night
previous (October 18, 2017 11:59:51 UT12), but had not been
initially identified by the object processing processor in
No other observatory seems to have observed it before.
Avi Loeb on ‘Oumuamua, Aliens, Space Archeology, Great Filters, and Superstructures
Future of Life Institute
Avi Loeb, Professor of Science at Harvard University, joins us to discuss a recent interstellar visitor, if we’ve already encountered alien technology, and whether we’re ultimately alone in the cosmos.
Topics discussed in this episode include:
-Whether ‘Oumuamua is alien or natural in origin
-The culture of science and how it affects fruitful inquiry
-Looking for signs of alien life throughout the solar system and beyond
-Alien artefacts and galactic treaties
-How humanity should handle a potential first contact with extraterrestrials
-The relationship between what is true and what is good
You can find the page for this podcast here:
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0:09 What is ‘Oumuamua’s wager?
9:09 The properties of ‘Oumuamua and how they lend credence to the theory of it being artificial in origin17:23 Theories of ‘Oumuamua being natural in origin’
20:48 Why was the smooth acceleration of ‘Oumuamua significant?
23:00 What are comets and asteroids?
28:32 What we know about Oort clouds and how ‘Oumuamua relates to what we expect of Oort clouds
34:03 Could there be exotic objects in Oort clouds that would account for ‘Oumuamua
38:56 What is your credence that ‘Oumuamua is alien in origin?
46:18 Bayesian reasoning and ‘Oumuamua
48:16 How do UFO reports and sightings affect your perspective of ‘Oumuamua?
57:17 Might alien artefacts be more common than we expect?
1:02:06 The Drake equation
1:05:29 Where are the most likely great filters?
1:18:37 Difficulties in scientific culture and how they affect fruitful inquiry
1:36:52 The cosmic endowment, traveling to galactic clusters, and galactic treaties
1:41:57 Why don’t we find evidence of alien superstructures?
1:47:44 Looking for the bio and techno signatures of alien life
1:52:30 Do alien civilizations converge on beneficence?
1:55:34 Is there a necessary relationship between what is true and good?
2:00:08 Is morality evidence based knowledge?
2:01:32 Axiomatic based knowledge and testing moral systems
2:08:17 International governance and making contact with alien life
2:10:25 The need for an elite scientific body to advise on global catastrophic and existential risk
2:15:02 What are the most fundamental questions?