CLEARED 02 For Open Publication Draft version March 1, 2023 Mar 08, 2023 Typeset using LATEX default style in AASTeX631 Department of Defense OFFICE OF PREPUBLICATION AND SECURITY REVIEW PHYSICAL CONSTRAINTS ON UNIDENTIFIED AERIAL PHENOMENA Abraham (Avi) Loeb1 and Sean M. Kirkpatrick2 1 Head of the Galileo Project, Astronomy Department, Harvard University 60 Garden Street, Cambridge, MA 02138, USA 2 All-domain Anomaly Resolution Office 1010 Defense Pentagon Washington DC 20301, USA ABSTRACT We derive physical constraints on interpretations of “highly maneuverable” Unidentified Aerial Phe- nomena (UAP) based on standard physics and known forms of matter and radiation. In particular, we show that the friction of UAP 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 U1) – Minor planets – ‘Oumuamua 1. INTRODUCTION In 2005, the US Congress tasked NASA to find 90% of all Near 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, Loeb (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-STARRS 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 ‘Oumuamua had. But the inclination of IM2’s orbital plane around the Sun was completely different from ‘Oumuamua’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 during its close passage to Earth, an operational construct not too dissimilar from NASA missions. These “dandelion seeds” could be separated from the parent craft by the tidal gravitational force of the Sun or by a maneuvering capability. A small ejection speed far away could lead to a large deviation from the trajectory of the parent craft near the Sun. The changes would manifest both in arrival time and distance of closest approach to Earth. With proper design, these tiny probes would reach the Earth or other Solar system planets for exploration, as the parent craft passes by within a fraction of the Earth-Sun separation - just like ‘Oumuamua did. Astronomers would not be able to notice the spray of mini-probes because they do not reflect enough sunlight for existing survey telescopes to notice them if they are on the 10 cm scale of CubeSats or smaller. At a distance d from the Sun and the telescope, objects that are a meter in diameter and reflect a fraction a ≈ 10% of sunlight impinging on their surface would yield a flux of optical light of ∼ 0.2(d/1 AU)−2 nJy, well below the detection threshold of even the James Webb All-Domain Anomaly Resolution Office Chief of Staff, AARO Page determined to be Unclassified Date: 2/5/2025 Reviewed by Chief of Staff, AARO Released in Full: X IAW FY24 NDAA, Section 1841(a)(1)(C) Authority: FY24 NDAA, now codified at 44 U.S.C. Date: 2/5/2025 2107 Case Number: 330UAP000002