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  • Avi Loeb

The Galileo Project: Looking Through the Window with New Telescopes

Avi Loeb

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I. Overview 


We cannot jump off the train of time as we age. It keeps going, so we better look through its windows and enjoy the ride while it lasts.

Life is a fascinating journey if we pay attention to the unusual sightings through the windows of our train cabin. From my perspective as an astronomer, the most unusual sighting over the past five years was that of the first interstellar object traced near Earth, `Oumuamua, appeared different from all solar system objects we had observed before. Its many anomalies led me to the intriguing hypothesis that it might be extraterrestrial equipment. The most natural action item derived from this experience was to collect more data on `Oumuamua-like objects in the future, in order to identify their nature. My realization led to the establishment of the Galileo Project on July 26, 2021, a month after the Office of the Director of National Intelligence (ODNI) delivered a report to Congress about other Unidentified Aerial Phenomena (UAP) whose nature is unclear.


Six months after the ODNI report, President Biden signed into law - with bipartisan support in Congress - the establishment of a new UAP office.  The office, to operate by June 2022, will have the authority to start a coordinated effort of reporting and responding to UAP and significantly improve data-sharing between government agencies on UAP sightings.


Complementing the classified government-owned data, the Galileo Project’s data will be open to the public and its scientific analysis will be transparent. The related scientific findings would expand humanity’s knowledge, with no attention to borders between nations.


By now, the Galileo research team includes more than a hundred scientists who plan to assemble the first telescope system on the roof of the Harvard College Observatory in spring 2022. The system will record continuous video and audio of the entire sky in the visible, infrared and radio bands, and track objects of interest. Artificial intelligence algorithms will distinguish birds from drones, airplanes or something else. Once the first system will operate successfully, the Galileo Project will make copies of it and distribute them in many geographical locations. The number of copies will depend on the funding level of the project at that phase.


I was recently asked why the search for extraterrestrial techno-signatures would be of interest to a common person, like a taxi driver worried about paying the rent. Interestingly, the congressional task for the new UAP office involves a science plan that aims to: “(1) account for characteristics and performance of unidentified aerial phenomena that exceed the known state of the art in science or technology, including in the areas of propulsion, aerodynamic control, signatures, structures, materials, sensors, countermeasures, weapons, electronics, and power generation; and (2) provide the foundation for potential future investments  to replicate any such advanced characteristics and performance.” The taxi driver would care about the second item if it would offer an opportunity for a higher paying job in driving a faster transportation device.


We should continue to revise our assessment of the cosmic environment we inhabit as we collect new data. It was recently reported that Jeff Bezos “observed that the smartest people are constantly revising their understanding, reconsidering a problem they thought they’d already solved. They’re open to new points of view, new information, new ideas, contradictions, and challenges to their own way of thinking.”  The reverse must also be true: the expectation by some researchers to make discoveries out of maintaining the status-quo implies a lack of intelligence and imagination.


Recently, I was approached by a colleague who saw a Boston Globe Magazine article and stated: “one can buy online large pictures of "famous" people... It's about time that you will be added.” In reply, I clarified: “this is not about me but rather the future of humanity. If the Galileo Project will photograph extraterrestrial equipment, this data would be far more important than my own picture.”


II. The First Interstellar Object: `Oumuamua

I. Anomalies


On October 19, 2017, the first object from outside the Solar system was discovered near Earth by the Pan STARRS telescope in Hawaii. It was given the name, `Oumuamua, which means `a messenger from afar, arriving first’ in the Hawaiian language (see Figure 1). I was intrigued by this first interstellar object because a decade earlier I co-authored a paper forecasting that Pan STARRS should not detect any rock from other stars based on what we know about the Solar system1.



Figure 1: Combined telescope image of the first interstellar object `Oumuamua, circled in blue as an unresolved point source at the center. It is surrounded by the trails of faint stars, each smeared into a series of dots as the telescope snapshots tracked the moving `Oumuamua. (Credit: ESO/K. Meech et al.)


Astronomers initially assumed that `Oumuamua is a comet, because comets are most loosely bound to the Sun, residing in the Oort cloud at the periphery of the Solar system where they can be easily sent to interstellar space by the perturbation of a passing star. But there was no visible cometary tail around `Oumuamua. Moreover, a cometary origin implies that `Oumuamua would have inherited the motion of its parent star. But instead it was found to originate from the so-called “Local Standard of Rest” (see Figure 2). This frame averages over the motions of all stars near the Sun, and only 1 in 500 stars is so much at rest as `Oumuamua was in that frame, before the Sun kicked it gravitationally2 (see Figure 3).

Figure 2: Sky path of `Oumuamua, labeled by date, as seen from Earth. The relative size of each circle gives a sense of the changing distance of `Oumuamua along its apparent trajectory. Also shown are the direction of motion of the Sun in the Local Standard of Rest (purple, labeled “Solar apex”), Venus (green), Mars (red) Uranus (turquoise) and the opposite direction to the motion of the Sun (purple, labeled “Solar antapex”). `Oumuamua’s trajectory moved from the Local Standard of Rest to south of the ecliptic plane (marked by the thin yellow line) of the Solar System between September 2 and October 22, 2017. (Credit: JPL Horizons) 


These were just the initial anomalies that made `Oumuamua different from all the comets and asteroids that we had seen before in the Solar system. As it tumbled every eight hours (see Figure 4), the brightness of sunlight reflected from it changed by a factor of ten. This meant that it has an extreme shape, which at the ~90% confidence level was disk-like3. The Spitzer Space Telescope did not detect any carbon-based molecules or dust around `Oumuamua, setting a tight limit on ordinary cometary activity4. The lack of heat - detectable in the infrared, placed an upper limit of about 200 meters on its size, the scale of a football field. But most remarkably, `Oumuamua exhibited an excess push away from the Sun which would have required it to lose ~10% of its mass if it was caused by the rocket effect from normal cometary evaporation5. An extensive evaporation of this magnitude was absolutely ruled out by the Spitzer telescope data; moreover, the repulsive force declined smoothly with distance from the Sun, showing no change in spin or sudden kicks as routinely observed from jets on the surface of comets6. Finally, there was no apparent cut-off in the push at the distance beyond which evaporation of water ice by sunlight is expected to stop (see Figure 5).

Figure 3: Trajectory of  `Oumuamua through the Solar System. Unlike all asteroids or comets observed before, this orbit is not bound by the Sun’s gravity. `Oumuamua originated from interstellar space and will return there with a velocity boost as a result of its passage near the Sun. Its hyperbolic orbit was inclined relative to the ecliptic plane of the Solar System and did not pass close to any of the planets on the way in.  (Credit: ESO/K. Meech et al.).

The excess force without a cometary tail convinced me that this object is not a familiar rock. Since the push away from the Sun was consistent with a smooth inverse-square law, I reasoned that it may result from the reflection of sunlight from a thin object7. For the reflection of sunlight to exert a strong enough force, the object had to be thinner than a millimeter, like a light sail. Since nature does not make thin objects, I suggested that it might be artificial in origin8-10.


Figure 4: Variation in brightness of `Oumuamua as observed by various telescopes during three days in October 2017. Different colored dots represent measurements through different filters in the visible and near-infrared bands of the color spectrum. The amount of reflected sunlight changed periodically by about a factor of ten (2.5 magnitudes) as `Oumuamua rotated every 8 hours. This implied that it has an extreme shape which is at least ten times longer than it is wide when projected on the sky. The dashed white line shows the curve expected if `Oumuamua were an ellipsoid with a 1:10 aspect ratio. However, the best fit to the light curve from its tumbling motion implies a flattened, pancake-shaped configuration rather than an oblong, cigar-shaped object as commonly depicted in the media.  (Credit: ESO/K. Meech et al.)


This possibility was intended to encourage scientists to obtain a high-resolution image of `Oumuamua-like objects in the future. It is often said that `a picture is worth a thousand words.’ In my case, a picture is worth 66 thousand words, the number of words in my book titled, Extraterrestrial. I would have never written this book if we had a megapixel image of `Oumuamua.

Figure 5:  Trajectory of `Oumuamua through the inner region of the Solar System, dated weekly. The planet positions are fixed at the time of `Oumuamua’s closest approach to the Sun (perihelion) on September 9, 2017.


In September 2020, another object11 was discovered by Pan STARRS sharing `Oumuamua’s anomalies of no cometary outgassing and excess push by reflection of sunlight. It was given the astronomical name 2020 SO and later found to be a rocket booster from a 1966 mission to the Moon. It had thin walls and hence a large area for its mass. It was not designed to be a light sail but was thin for a different purpose. Its discovery illustrates that the difference between a rock and an artificial object can be inferred from the unusual dynamics of an object. We know that humanity manufactured 2020 SO. The question is who manufactured `Oumuamua?


A cave dweller finding a cellphone would argue that it is a rock of a new type, in the same way that earthlings who studied the anomalies of the first interstellar object `Oumuamua suggested that it is a comet of a type “never seen before”, such as an iceberg made of pure hydrogen or pure nitrogen, even though these possibilities face “serious difficulties” in the words of some of their proponents12. When a colleague of mine, specializing in solar system rocks, heard about `Oumuamua, he said: “this interstellar object is so weird … I wish it never existed.” His statement explains why innovation is often suppressed in the face of anomalies. Mainstream scientists would prefer these anomalies to go away in order to maintain the prestige that they can forecast all data with their existing knowledge. They find anomalies to pose a threat to their status as “experts” in the field.


II. Possible Natural Origins and Their Challenges


Astronomers who attempted to explain the anomalies of `Oumuamua by a natural origin were all forced to contemplate objects that were never seen before, with major quantitative challenges. These possibilities are:

(i)  a porous structure with a mean density a hundred times lower than air13-14 - which is unlikely to maintain its integrity after being heated to hundreds of degrees by the Sun;

(ii) fragments from tidal disruption15 – whose shape is more likely to be that of a cigar than a disk as inferred for `Oumuamua;

(iii) an iceberg of molecular hydrogen16 – which evaporates too quickly along its interstellar journey17 (see Figure 6);

(iv) a nitrogen iceberg chipped off the surface of a planet like Pluto around another star18 – a mechanism that cannot supply enough material to explain the implied abundance of objects like `Oumuamua12,19-20 (see Figure 7).

Figure 6: Comparison of various destruction timescales for a hydrogen H2 iceberg (slanted colored lines) as a function of the object radius (in meters) to the travel time from the likely source of a giant molecular cloud at a distance of 5.2 kpc, assuming a characteristic speed of 30 km s−1 (horizontal black line). (Credit: Ref. 17)

Figure 7: Erosion time by cosmic rays for various types of ices including nitrogen N2 (solid red line), CO (dashed green line), CO2 (dotted blue line), and CH4 (dash-dot magenta line) in comparison with the suggested travel time of ~0.5 Gyr for ‘Oumuamua (solid black line). A short travel time, would imply origin from nearby young stars, which are much less abundant than old stars. This makes the required nitrogen mass budget untenable. (Credit: Ref. 20)


III. The Possibility of an Artificial Origin


Given these challenges to natural origins of `Oumuamua and the similarity in the anomalous dynamics of 2020 SO and `Oumuamua, the possibility of an artificial origin should be left on the table (see Figure 8).

Figure 8: Artist’s impressions of two possible shapes for `Oumuamua. The object’s length is estimated to be between tens to hundreds of meters, up to the size of a football field. It is either an oblong, cigar-shaped rock - as depicted in the upper image (Credit: ESO/M. Kornmesser), or a flattened, pancake-shaped object - as shown in the lower image (Credit: Mark Garlick). The pancake shape provides the best fit to `Oumuamua’s light curve3. Even a razor-thin object, like a flat sheet of paper, would appear to possess some width when projected at a random orientation on the sky, so the intrinsic aspect ratio of `Oumuamua can be much smaller than the value of 1:10 inferred from its light curve.


Thanks to the generous donations from people who were inspired by the vision of my book Extraterrestrial, I was able to inaugurate on July 26, 2021 the Galileo Project21. One of the major goals of the project is to search for `Oumuamua-like objects in future surveys, like with the upcoming Vera Rubin Observatory. An early alert to `Oumuamua-like objects would allow to design of a space mission that will intercept their trajectories and take close-up photographs of them. Such data could resolve their nature and unambiguously determine whether they are natural or artificial in origin.


Finding equipment from an extraterrestrial technological civilization would have a major impact on the future of humanity. Here’s hoping that we will be open minded enough to search for objects that resemble the equipment that our technological civilization is launching to space. We know that half of the Sun-like stars host a planet the size of the Earth roughly at the same separation22. Many of these stars formed billions of years before the Sun, allowing for the possibility that numerous probes were sent to interstellar space. Ridiculing the notion that `Oumuamua may have been artificial in origin will not get rid of our neighbors23. As Galileo Galilei instructed us four centuries ago, the nature of celestial objects must be found through our telescopes rather than philosophical prejudice.


III. The Galileo Project


The Galileo Project is a search for extraterrestrial equipment near Earth. It has two branches: the first aiming to identify the nature of interstellar objects that do not resemble comets or asteroids, like `Oumuamua; and the second targets Unidentified Aerial Phenomena (UAP), similar to those mentioned in the recent ODNI report to the US Congress.


The Galileo Project has drawn a remarkable base of expert volunteers, from astrophysicists and other scientific researchers, to hardware and software engineers, to non-science investigators and generalists who volunteer their time and effort to the project in various ways. The project brings together a broad community of research affiliates, including UAP advocates like Lue Elizondo, Chris Mellon or Nick Pope and skeptics like Seth Shostak or Michael Shermer, united by the pursuit of evidence through new telescopes without prejudice.


The project values the input of many different voices, and the rapid progress it already made, is a testament to its open approach. As different as the perspectives of the researchers and affiliates may be, however, every contributor to the Galileo Project is bound by three ground rules:


(i) The Galileo Project is only interested in openly available scientific data and a transparent analysis of it. Thus, classified (government-owned) information, which cannot be shared with all scientists, cannot be used. Such information would compromise the scope of our scientific research program, which is designed to acquire valid scientific data and provide transparent (open to peer review) analysis of this data. Indeed, the Galileo Project will work only with new data, collected from its own telescope systems, which are under the full and exclusive control of Galileo research team members.


(ii) The analysis of the data will be based solely on known physics and will not entertain fringe ideas about extensions to the standard model of physics. The data will be freely published and available for peer review as well as to the public, when such information is ready to be made available, but the scope of the research efforts will always remain in the realm of scientific hypotheses, tested through rigorous data collection and sound analysis.


(iii) To protect the quality of its scientific research, the Galileo research team will not publicize the details of its internal discussions or share the specifications of its experimental hardware or software before the work is finalized. The data or its analysis will be released through traditional, scientifically-accepted channels of publication, validated through the traditional peer-review process.


All members of the Galileo Project team, including researchers, advisors and affiliates, share these values and uphold the principles of open and rigorous science upon which the Galileo Project is founded.

While browsing the internet, I came across an interesting statement about UAP made by the former Director of National Intelligence, John Ratcliffe, in a Guardian article dated March 22, 2021: "we are talking about objects that have been seen by navy or air force pilots, or have been picked up by satellite imagery, that frankly engage in actions that are difficult to explain, movements that are hard to replicate, that we don’t have the technology for." 


The part that caught my attention is the reference to "satellite imagery" because I had never seen any publicly released data on that. The hundred scientists engaged in the newly established Galileo Project would be extremely interested in analyzing any data on objects that enter the Earth's atmosphere and do not follow ballistic orbits like meteors. But no such data is currently available to open scientific analysis.


Of course, Ratcliffe’s quote is an insufficient basis for substantive scientific inquiry. But unclassified data, assembled by non-governmental satellites, could be made available to open scientific analysis by the Galileo Project.


Protocols for a possible contact with extraterrestrial intelligence were mostly inspired in the past by the possibility of detecting radio signals from planets around distant stars. Given that the nearest star system, Alpha Centauri, is 4.4 light years away, such signals would require a decade or more for a round-trip conversation. As a result, they do not bear consequences to our immediate future.


But a different type of contact could deliver prompt implications. It concerns physical objects from another civilization that are already here, waiting to be noticed like a package in our mailbox. The arriving hardware need not be brainless but could possess artificial intelligence (AI) - seeking information about the habitable planets around the Sun.


An encounter of this type implies instant contact without a significant delay in communication time. The potential for an immediate engagement changes the response protocol relative a delayed radio signal.


Currently, there is no international agreement on how humanity should engage with a visiting object of extraterrestrial origin. It would be prudent to formulate guidelines before they are needed. Any engagement could have implications for the future of humanity and should not be left to the spontaneous whims of a small team of researchers.


We should weigh the risks and benefits that will result from different engagements. The decision tree on how to proceed will have branches that depend on the objects’ properties and behavior. Since it is difficult to forecast these unknowns in advance, decisions will have to be reached in real time.


Deciphering the intent of an intelligent extraterrestrial equipment may resemble the challenge of breaking the code of an encryption device. We might need to rely on our AI systems in figuring out the intent of extraterrestrial AI systems.


A proper interpretation of prompt contact with extraterrestrial technologies could bring about the most significant advance in understanding of the reality around us in the entire history of humans. Our historic migration out of Africa started about a hundred thousand years ago, but our future migration out of Earth may be triggered by a dialogue with a messenger from afar that does not resemble anything we had seen before.


Abraham (Avi) Loeb is the Frank B. Baird, Jr., Professor of Science at Harvard University and a bestselling author (in lists of the New York Times, Wall Street Journal, Publishers Weekly, Die Zeit, Der Spiegel, L’Express and more). He received a PhD in Physics from the Hebrew University of Jerusalem in Israel at age 24 (1980-1986), led the first international project supported by the Strategic Defense Initiative (1983-1988), and was subsequently a long-term member of the Institute for Advanced Study at Princeton (1988-1993). Loeb has written 8 books, including most recently, Extraterrestrial (Houghton Mifflin Harcourt, 2021), and about 800 papers (with an h-index of 117) on a wide range of topics, including black holes, the first stars, the search for extraterrestrial life and the future of the Universe. Loeb is the Director of the Institute for Theory and Computation (2007-present) within the Harvard-Smithsonian Center for Astrophysics , and also serves as the Head of the Galileo Project (2021-present). He had been the longest serving Chair of Harvard’s Department of Astronomy (2011-2020) and the Founding Director of Harvard’s Black Hole Initiative (2016-2021).



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