"Obiekt międzygwiezdny pochodzenia nienaturalnego potencjalnie mógłby być statkiem bazą, uwalniającym wiele małych sond podczas swojego przelotu w pobliżu Ziemi, taka operacja w swojej koncepcji nie odbiegałaby wiele od misji ktorych podejmuje się NASA." - Sean Kirkpatrick, director of the Pentagon’s All-domain Anomaly Resolution Office, wrote in a research report co-authored by Abraham Loeb, chairman of Harvard University’s astronomy department.
Tucker Carlson’s, też zaczyna mówić dziwne rzeczy.https://twitter.com/...297925248638976
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DRAFT VERSION MARCH 4, 2023
Typeset using default Style in AASTeX631
PHYSICAL CONSTRAINTS ON UNIDENTIFIED AERIAL PHENOMENA
ABRAHAM (Avo LOEB I AND SEAN M. KIRKPATRICK*
I Head OJ the Galileo Project, Astronomy Department, Harvard Untversity
60 Garden Street, Cambridge, MA 02138, USA
Director Of All-domain Anomaly Resolution ODice
1010 Defense Pentagon
Washington DC 20301, USA
ABSTRACT
WO derive physical constraints on interpretations of "highly maneuverable" Unidentified Aerial Phenomena (UAP) based on standard physics and known forms of matter and radiation. In particular, we show that the friction of [JAP with the surrounding air or water is expected to generate a bright optical fireball, ionization shell and tail - implying radio signatures. The fireball luminosity scales with inferred distance to the 5th power. Radar cross-section scales similarly to meteor head echoes as the square of the effective radius of the sphere surrounding the object, while the radar cross-section of the resulting ionization tail scales linearly with the radius of the ionization cylinder. The lack of all these signatures could imply inaccurate distance measurements (and hence derived velocity) for single site sensors without a range gate capability.
Keywords: Interstellar objects — Meteors — meteoroids — Meteorites — Bolides — asteroids: general — asteroids: individual (A/2017 UI) — Minor planets — 'Oumuamua
1. INTRODUCTION
In 2005, the US Congress tasked NASA to find 90% of all NOar Earth Objects (NEOs) that are larger than 140 meters (Loff 2014). The Congressional task resulted in the construction of the Pan-STARRS telescopes. On October 19, 2017, the Pan-STARRS sky survey flagged an unusual NEO, the interstellar object 'Oumuamua (see, Loéb (2022a) and references therein). Unlike Solar system asteroids or comets, 'Oumuamua appeared to have an extreme flat shape and was pushed away from the Sun without showing a cometary tail of gas and dust, raising the possibility that it, was thin and artificial in origin. Three years later, Pan-STAR,RS discovered a definitely artificial object, namely NASA's rocket booster 2020 SO, which exhibited similar behavior with an extreme shape, a push by the Solar radiation pressure and no cometary tail because its thin walls were made of stainless steel (Talbert 2020).
On March 9, 2017, six months before 'Oumuamua's closest approach to Earth, a meter-size interstellar meteor (IM2) collided with Earth (Siraj Loeb 2022a), Surprisingly, IM2 had an identical speed relative to the Sun at large distances and an identical heliocentric semimajor axis as COumuamua had. But the inclination of IM2's orbita.l plane around the Sun was completely different from 'Oumuarnua's, implying that the two Objects are unrelated.
Nevertheless, the coincidences between some orbital parameters of 'Oumuamua and IM2 inspires us to consider the possibility that an artificial interstellar object could potentially be a parent craft that releases many small probes Space Telescope. In contrast, the radar signatures of a meter class object would be detectable with our deep space radars and space fence, much like IM2 was, out to beyond geosynchronous orbit at an altitude above 36,000 km. Such objects could also become optically detectable as they get close to Earth, especially if they create a fireball as a result of their friction with air.
Equipped with a large surface-to-mass ratio of a parachute, technological "dandelion seeds" could slow down in the Earth's atmosphere to avoid burnup and then pursue their objectives wherever they land. Current radar coverage of the majority of first-world countries gives detectability of this High-Area-To-Mass (HAMR) objects down to a few centimeters depending on material, making detectability possible (Frueh et al. 2017).
Within a close range to a star, extraterrestrial technological probes could use starlight to charge their batteries and liquid water as their fuel. This would explain why they would target the habitable region around stars, where liquid water may exist on the surface of rocky planets with an atmosphere, like the Earth. Habitable planets would be particularly appealing to trans-medium probes, capable of moving between space, air and water. From a large distance, Venus, Earth or Mars would be equally attractive for probes. But upon closer inspection, Earth would show spectral signatures of liquid water (through reflection of blue light) and vegetation (through its red edge) that might attract selective attention (Seager et al. 2005).
What would be the overarching purpose of the journey? In analogy with actual dandelion seeds, the probes could propagate the blueprint of their senders. As with biological seeds, the raw materials on the planet's surface could also be used by them as nutrients for selßreplication or simply scientific exploration. It is important to note, that given the time scales associated with the propulsion scheme discussed here, it is unreasonable to assert that the intention of any such probe launched in the far distant past, has anything to do with the human species. More likely, and similar to NASA's missions — the goal would be scientific and exploratory in nature.
Based on the detection rate of interstellar objects, Siraj Loeb (2022b) estimated that for every interstellar NEO there are a thousand Solar system NEOs of the same size. Searching for interstellar meteorites among the many more meteorites from the Solar system without information about impact velocity, is like searching for a needle in a haystack.
This is why the first interstellar meteor (IMI), confirmed by velocity measurement of the US Space Command (Siraj & Loeb 2022c), is the target of a fully-funded ocean expedition by the Galileo Project (Siraj et al. 2022; Tillinghast-Raby et al. 2022). Hopefully, by retrieving IMI's fragments within the coming year we will know whether its extraordinary material strength resulted from it being made out of an artificial alloy, like stainless steel or materials not yet developed by humans.
Are there any functioning extraterrestrial probes near Earth? We do not know. But the Galileo Project (2021) (Loeb 2021) intends to use the scientific method to explore this possibility, following the 2021 report about Unidentified Aerial Phenomena (UAP) from the Office of the Director of National Intelligence to the US Congress (ODN 2021). The stateof-the-art suite of instruments and computer algorithms of the Galileo Project will be able to study such data in the near future (Loeb & Laukien 2023).
The search for UAP, and the characterization of UAP, requires bounding the search plan with physics-based constraints on what we are searching for. This paper aims to constrain one aspect of the UAP hypothesis with parameters that govern the movement and interaction of a UAP with Earth's atmosphere to eliminate or bound observational uncertainties. Some data collected to date, while arising from multiple sensors, have uncertainties in one or more dimensions, leaving the exploitation of the data with a significant range of interpretations. This inevitably leaves open the debate on what some objects are, and whether or not they exhibited truly anomalous behavior. Specifically, if some observed UAP are of extraterrestrial origin, there are some practical limits on the interpretation of observed and
CONSTRAINTS ON UAP 3
light years that span the scale of the Milky Way galaxy. Such autonomous systems could be designed to survive even if the senders are not able to communicate with them, and deposit probes upon arrival to the target planetary systems.
It is likely that any functional devices embedded in the Earth's atmosphere are not carrying biological entities because these would not survive the long journey through interstellar space and its harsh conditions, including bombardment by energetic cosmic rays, X-rays and gamma-rays (Hoang et al. 2017, 2018; Hoang Loeb 2020). Interstellar gas and dust particles deposit a kinetic energy per unit mass that exceeds the output of chemical explosives at the speed of tens of km/s. However, technological devices with Al can be shielded to withstand the hazards of space, repair themselves mechanically, or even reproduce given the resources of a habitable planet like Earth. With Machine Learning capabilities, they can adapt to new circumstances and pursue the goals of their senders without any need for external guidance.
As argued by John von Neumann in 1939, the number of such devices could increase exponentially with time if they self-replicate (Freitas 1980), a quality enabled by 3D printing and Al technologies. Physical artifacts might also carry messages, as envisioned by Ronald Bracewell in 1960Z (Bracewell 1960; m•eitas & Valdes 1985) and currently used by NASA.
3. PROPULSION METHODS
In principle, the fastest devices could be launched by lightsails, pushed by powerful light beams up to the speed of light (Guillochon & Loeb 2015a). Natural processes, such as stellar explosions (Loeb 2023; Lingam & Loeb 2020) or gravitational slingshot near black hole pairs (Guillochon & Loeb 2015b; Loeb Guillochon 2016), could launch objects to similar speeds. However, it would be difficult for relativistic payloads to slow down below the escape speed of Earth, 10—4.5c, without having around the same facilities that generated their high initial speeds.
A better-suited propulsion technique that was used in all interplanetary space missions from Earth is chemical rockets. Since rockets carry their fuel, they can navigate to a desired planet and slow down near it. Alternatively, it may be possible to use one of the above methods to travel to and through a planetary system, deploying interplanetary probes using conventional chemical propulsion,
For a rocket of total mass, m, and exhaust speed of the ablated gas relative to the rocket, vexh, momentum conservation implies: ml,' —rhvexh, where an overdot, ( ), denotes a partial time derivative. The Tsiolkovsky solution to the rocket equation (Tsiolkovsky 2000), (minitial/rnfinal) — Vinitial)/vexh}, implies that for a reasonable fuel-to-payload mass ratio, the final speed Vfinal will only be an order of magnitude larger than the exhaust speed. For typical chemical propellants with vexh of order a few km s 1 , this tyranny of the rocket equation explains why all human-made spacecraft reached a speed limit of tens of km s¯ or 10 ¯4 c. Interestingly, this speed is comparable to the escape speed from the Earth's orbit around the Sun, 'Vesc 42km s making if, possible for humanity to launch interstellar probes which take advantage of the motion of the Earth around the Sun at 30 km s In contrast, chemical propulsion may not be sufflcient for probes to escape from the habitable zone around dwarf stars, like the nearest star, Proxima Centuari (Loeb 2018; Lingam & Loeb 2018). In summary, chemical propulsion allows escape from the habitable zone of Sun-like stars and enables slowing down near a destination.
Devices which need to refuel would favor a habitable planet where liquid water or combustible organic fuel are available. The exhaust velocity of hydrogen/oxygen for rocket fuel is about 4.5 km s—1 (at a mass ratio of 16.4 with steam as exhaust) and so pure liquid hydrogen/oxygen is insufficient to slow down the characteristic free-fall speed of over 40 km from interstellar space to the habitable zone around the Sun unless the fuel mass is many orders of magnitude larger than the payload mass. Combustion of fuels with potentially higher heat capacity (such as hydrocarbons) would result in other chemical byproducts at the craft's exhaust, which would have distinct spectral et al, 2021). This implies that self-replicating probes could reach 10 10 habitable planets around Sun-like stars in less than a billion years. Since most stars formed more than a billion years before the Sun (Madau & Dickinson 2014), it is possible that other technological civilizations predated ours by the amount of time needed for their devices to reach Earth,
Here we can use time as another constraint. In the propulsion scheme where an interstellar self-replicating au tonomous system is travelling at 10¯4 c, the above analysis argues that 10 10 habitable planets around Sun-like stars could be reached within 0.5 Gyr. These self-replicating systems would necessarily be looking for water in order to generate fuel, and would necessarily have to take into account the relative motion of the planet in order to reach escape velocities after completion of the exploration mission. 1 Gyr ago Earth had water coverage and some simple algae plant life. In the extreme, detection of Earth 1 Gyr ago from a technological civilization near the center of the Milky Way 0.5 Gyr ago would be needed to decide to intentionally navigate here. In doing so, the navigators would need to plan for where the solar system would be located 1 Gyr in the future from their point of observation. Under such considerations, if becomes more likely that either: (i) such interstellar probes are the result of an unintended arrival to a planetary system; (ii) a technological civilization much closer to us than the center of the Milky Way; or (iii) an alternative propulsion scheme like the mothership/probe system is used.
A detailed statistical analysis by Ezell Loeb (Ezell & Loeb 2022) showed that the inferred abundance of probes is distinctly different in case of objects being targeted towards particular regions of the galaxy, specifically habitable zones containing planets. 'Ournuamua was detected at a distance of 0.2 AU from Earth, and it passed through the habitable zone of our solar system. The estimated total number of 'Oumuamua-like objects would then fall by a factor of 2 x 1010 in the case of targeted probes compared to probes on random trajectories.
The interstellar meteor IMI had an estimated diameter of 0.45 m and velocity of 60 km but it was detectable when it burned up within the atmosphere of the Earth (Siraj & Loeb 2022a). The estimated detection rate for meter-size interstellar meteors is at least O.lyr¯l (Siraj & Loeb 2022a), resulting in a local density estimate of 106 AU 3 1022 pc This implies 8 x 1034 IMI-like objects bound by the thin disk of the Milky Way. However, if objects with the properties of IMI were targeted towards habitable zones containing planets, the required number of such objects is merely 4 x 1024 . IM2 had a similar inferred number density to IMI and a velocity of 40 km s 1 relative to the Local Standard of Rest (Siraj Loeb 2022a). This implies 3 x 1034 IM2-like objects, with a reduction to 1.5 x 1024 if such objects were targeted towards habitable zones.
The actual abundance of interstellar objects can be calibrated through future surveys such as the Legacy Survey of Space and Time (LSST) on the Vera C. Rubin Observatory in Chile. Parallax data from the James Webb Space Telescope may identify the nature and 3D trajectory of more T)umuamua-like or smaller interstellar objects crossing through or trapped within the solar system.
Below we show that any supersonic motion by such devices through the Earth's atmosphere would inevitably be accompanied by bright optical emission and detectable characterization signatures.
4. OPTICAL EMISSION
An object made of known matter with a frontal cross-sectional area A, moving at a supersonic speed, v, must create a bow shock in the Earth's atmosphere and dissipate a mechanical power,
p —Apav3 1.5TW(A/10 km s (1)
where pa is the ambient air density which depends on elevation, normalized here by a representative value at an
CONSTRAINTS ON UAP 5
In addition to the thermal, shock, and associated optical signatures of a high velocity, highly maneuvering object, there is also an ionization and associated radio frequency signature from such an object moving through the atmosphere, Studies into supersonic and hypersonic vehicles provide a good basis for comparison. While the ionization density depends on the altitude, shape, material and velocity of the object in motion, some limits can be derived on when a signature would be detected, implying a limit to the object's motion prior to the fireball threshold. In particular, ionization at high velocities leads to an increase in radar reflectivity along the ionization edge of the object and along the ionization trail. Both give rise to enhanced radio-frequency (RF) reflection for frequencies below the cutoff frequency.
Surzhikov calculates the ionization of air in high supersonic and low hypersonic regimes around blunt air frames (Surzhikov 2018). Figure 2 and table 1 in Surzhikov (2018) demonstrate the lowest end giving rise to a critical electron density of 1010 cm ¯3 for detection frequencies between 1-10 GHz. Variations of velocity, altitude and shape give rise to electron densities above this threshold, rendering the object detectable for typical radars in the L, S, C, and X radio bands.
Dhakal et al. conducted an excellent assessment of constraints on dark matter using radar meteor detectors (Dhakal et al. 2022). While not directly applicable to the current span of UAP sightings, the calculations do address smaller, faster objects at higher altitudes (70-130 km). These objects also exhibit an ionization trail which can be used for detection and measurement using similar radars. This regime is relevant to the mothership/probe scenario discussed above, indicating a detectable signature prior to the onset of a fireball as shown in Figures (1) and (11) of Dhakal et al. (Dhakal et al. 2022).
6. CONCLUSION
The considerations in this paper imply a useful limit on observations of UAP which bound the hypothetical explanations and can support limitations on interpretations of data. For example, one of the most common sets of data within the military holdings comes from FLIR (forward looking infrared) pods, These sensors provide an accurate resolved image of relative thermal measurements across the scene. Typical UAP sightings are too far away to get a highly resolved image of the object and determination of the object's motion is limited by the lack of range data. The range is usually estimated using the flight dynamics of the platform and some fixed points in the scene if either are available. The error in estimating the range gives rise to a significant variation in the calculated velocity and is subject to human bias and error.
Claims of objects exceeding the transonic to supersonic range should be evaluated against the above known physics of ionization, radar reflectivity, temperature, sonic booms, and fireballs (Loeb 2022b). All of which can more effectively and accurately bound the velocity, and hence drive the range calculation. This will, in turn, when matched with the specifics of the sensor, allow for better estimates of the size, shape, and mass of the object in question.
ACKNOWLEDGEMENTS. This work was supported in part by Galileo Project at Harvard University and conducted in partnership with the Department of Defense, All-domain, Anomaly Resolution Office. We thank Richard Cloete for assistance and comments on the manuscript.
2021, ODNI UAP Rcportl, USG.
REFERENCES
Dhakal, P. , Prohira, S., Cappicllo, C. V., et al. 2022, arXiv
