arXiv subjects

Abraham Loeb

Publications and source records attributed to Abraham Loeb.

At least 55 records · Page 3Linked to original sources

arXiv2025

Flux of Extragalactic Dark Matter in Direct Detection Experiments

We calculate the contribution of extragalactic dark matter to the local dark matter density and flux in the Milky Way. By analyzing the Galactic escape velocity as a function of direction, we establish the criterion for separating dark matter particles bound to the Milky Way and those originating from the Local Group environment. Our analysis reveals that approximately 25% of dark matter particles in the Solar neighborhood have an extragalactic origin, contributing nearly 38% of the total mass flux. The directional dependence of this extragalactic component shows significant anisotropy across the sky, with implications for direct detection experiments. We provide quantitative predictions for detection rates and signatures that could help identify the extragalactic dark matter component in current and future experiments.

hep-ph↗

arXiv2025

Is the Interstellar Object 3I/ATLAS Alien Technology?

At this early stage of its passage through our Solar System, 3I/ATLAS, the recently discovered interstellar interloper, has displayed various anomalous characteristics, determined from photometric and astrometric observations. As largely a pedagogical exercise, in this paper we present additional analysis into the astrodynamics of 3I/ATLAS, and hypothesize that this object could be technological, and possibly hostile as would be expected from the 'Dark Forest' resolution to the 'Fermi Paradox'. We show that 3I/ATLAS approaches surprisingly close to Venus, Mars and Jupiter, with a probability of $\lesssim 0.005$\%. Furthermore the low retrograde tilt of 3I/ATLAS's orbital plane to the ecliptic offers various benefits to an Extra-terrestrial Intelligence (ETI), since it allows the object access to our planet with relative impunity. The eclipse by the Sun from Earth of 3I/ATLAS at perihelion, would allow it to conduct a clandestine reverse Solar Oberth Manoeuvre, an optimal high-thrust strategy for interstellar spacecraft to brake and stay bound to the Sun. An optimal intercept of Earth would entail an arrival in late November/early December of 2025, and also, a non-gravitational acceleration of $\sim{5.9} \times 10^{-5}$ au day$^{-2}$, normalized at 1 au from the Sun, would indicate an intent to intercept the planet Jupiter, not far off its path, and a strategy to rendezvous with it after perihelion.

astro-ph.EP↗

arXiv2025

Comparison of Australasian tektites with Australasian microtektites and BeLaU spherules recovered from the ocean

The Australasian strewn field covers more than 15% of Earth's surface, consisting of tektites and microtektites. Australasian tektites from Southeast Asia and Australia, as well as microtektites recovered from deep sea sediments and Antarctica, are established to be derived from upper continental crust sediments. An expedition to retrieve remnants of bolide CNEOS 2014 January 8 (IM1), held in the Pacific Ocean, was in proximity to the known extent of the Australasian strewn field, and yielded "BeLaU"-spherules, whose compositions did not match most well-studied solar system material. We therefore report precise and comprehensive elemental data for Australasian tektites to compare their elemental abundances to those of microtektites from deep sea sediments, and BeLaU. Our findings corroborate previous studies that Australasian tektites and microtektites closely resemble the elemental abundance patterns of the upper continental crust. Meanwhile, the elemental patterns of the BeLaU-spherules are distinct from the Australasian tektite/microtektite compositions.

physics.geo-ph↗

arXiv2025

Advancing Interstellar Science: A Global Framework for Comprehensive Study of Interstellar Objects

The operation of the Vera C. Rubin Observatory's Legacy Survey of Space and Time (LSST) marks a transformative moment in humanity's capacity to detect and characterize interstellar objects (ISOs). With projections indicating an increase from a few detections per decade to potentially one every few months, humanity stands at the threshold of unprecedented scientific opportunity offering revolutionary insights into the nature of rocky materials, building blocks of life and technological products from other star systems. This white paper proposes the establishment of the United Nations Committee on Interstellar Objects (UNCIO), a specialized body designed to coordinate global scientific research, maximize observational coverage, and ensure optimal scientific return from these extraordinary objects from outside the solar system through systematic investigation in cosmochemistry, astrobiology, planetary sciences, fundamental physics, advanced technologies and materials science. The proposed framework addresses critical gaps in our current international infrastructure: the absence of coordinated detection, classification and intercept capabilities, insufficient protocols for rapid scientific response and international policy decisions to time-sensitive observations, and the need for effective science communication to maintain government and public support for these ambitious investigations and global threats to Earth. Drawing from successful international collaborations in areas such as the International Space Station (ISS) and the European Organization for Nuclear Research (CERN), UNCIO would operate through a dual structure: an executive board for time-critical scientific decisions and an expanded committee for comprehensive stakeholder representation. This initiative is not merely aspirational but urgently practical.

astro-ph.IM↗

arXiv2025

Upper Limit on the Non-Gravitational Acceleration and Lower Limits on the Nucleus Mass and Diameter of 3I/ATLAS

We use astrometric data on 3I/ATLAS compiled by the Minor Planet Center from May 15 to September 23, 2025, and derive an upper limit on any statistically significant deviation from the best-fit gravity-based trajectory. The residuals imply that the non-gravitational acceleration is smaller than $\sim 3 \times 10^{-10}\,{\rm au\,d^{-2}}$. Based on the total mass-loss rate and outflow speed inferred from JWST data on August 6, 2025, we derive lower limits on the mass and diameter of 3I/ATLAS of $3.3 \times 10^{16}\,{\rm g}$ and $5\,{\rm km}$, respectively.

astro-ph.EP↗

arXiv2025

Gaussian Planck Relics are Ruled-Out as Dark Matter by LIGO

Quantum Gravity models suggest that singularities in gravitational collapse can be replaced by bounces, leading to the formation of Planck star remnants (PSR) that survive as stable relics once the black holes evaporate to the Planck mass. Recently, we proposed that such relics can be a viable candidate for dark matter. Here we show that LIGO's upper limit on the gravitational wave background rules out a formation pathway of Planck mass relics as dark matter from Gaussian initial conditions. This leaves non-Gaussian primordial fluctuations as the only viable channel for making Planck mass relics as dark matter.

astro-ph.CO↗

arXiv2025

Exotic Dark Matter and the DESI Anomaly

Exotic dark matter (EDM) refers to a dark matter species whose equation of state deviates from zero at late times. This behavior enables it to model a variety of non-standard late-time cosmologies, offering alternatives to various dark energy (DE) models, especially when the DE sector violates the null energy condition. In this work, by fitting to CMB, BAO, and Supernovae (SNe) data and comparing models in a Bayesian approach, we show that simple models of exotic dark matter are statistically comparable to the $w_0w_a$CDM DE model in explaining the recent anomaly in the late-time cosmological evolution suggested by DESI and supernova observations, although in both classes of models the evidence against the $Λ$CDM model only appears when the DES-Y5 or Union3 SNe dataset is included. The value of $H_0$ remains similar to that in the DE model, except in the no-SNe case, where the DE model predicts lower values than $Λ$CDM, thereby worsening the Hubble tension, whereas the EDM models yield values closer to that of $Λ$CDM, albeit with larger uncertainty. In addition, the EDM models predict a drastically different energy budget for the present-day universe compared to the standard model, and provide an explanation for a coincidence problem in the DE-model explanation of the DESI anomaly.

astro-ph.CO↗

arXiv2025

Intercepting 3I/ATLAS at Closest Approach to Jupiter with the Juno spacecraft

The interstellar object 3I/ATLAS is expected to arrive at a distance of $53.56(\pm 0.45)$ million ${\rm km}$ ($0.358\pm 0.003$~au) from Jupiter on March 16, 2026. We show that applying a total thrust $Δ$V of $2.6755 {\rm km~s^{-1}}$ to lower perijove on September 9, 2025 and then execute a Jupiter Oberth Maneuver, can bring the Juno spacecraft from its orbit around Jupiter to intercept the path of 3I/ATLAS on March 14, 2026. We further show that it is possible for Juno to come much closer to 3I/ATLAS ($\sim{27}$ million km) with 110 kg of remaining propellant, merely 5.4% of the initial fuel reservoir. We find that for low available $Δ$V there is no particular benefit in application of a double impulse (for example to reach $\sim{27}$ million km from 3I/ATLAS), however if Juno has a higher $Δ$V capability there is significant advantage to a second impulse with typically a saving of propellant by a factor of a half. A close fly-by might be able to probe the nature of 3I/ATLAS far better than telescopes on Earth.

astro-ph.EP↗

arXiv2025

Quantitative Mapping of the Loeb Scale

The recent discovery of a third interstellar object (ISO) 3I/ATLAS, following 1I/`Oumuamua and 2I/Borisov, has raised questions about the nature and origin of these enigmatic objects. With the Vera C. Rubin Observatory expected to discover dozens of new ISOs over the next decade, it is timely to use a classification scheme for their nature in the context of the recently proposed Loeb scale. Here, we provide a formalism for ranking ISOs quantitatively on the Loeb Scale in analogy to Sagan's formalism for mapping the Kardashev scale based on the energy output of technological civilizations.

astro-ph.EP↗

arXiv2025

Dynamical Constraints on a Population of Massive Interstellar Objects

We investigate dynamical constraints on the population of large interstellar objects (ISOs) by combining encounter rate analysis, Eddington inversion, and Liouville mapping. Encounter rate scaling demonstrates that detections of kilometer-scale ISOs require flux enhancements beyond natural Maxwellian expectations. Using Eddington inversion, we show how steep density profiles imply phase-space biases consistent with strong gravitational focusing and we then develop a Liouville mapping formalism that propagates the interstellar velocity distribution inward under conservation of energy and angular momentum, revealing that low-angular momentum anisotropies can reproduce the observed size dependent detection rates. These results provide a self consistent dynamical framework for interpreting the observed population of ISOs and for assessing whether the required anisotropies arise from natural or artificial origins. The main results are framed in the context of the parameters for 3I/ATLAS, but the implications are general and go on to sharpen the distinction between natural dynamical mechanisms and potential artificial origins for ISOs.

astro-ph.EP↗

arXiv2025

Inconsistency with De Sitter Spacetime in a New Approach to Gravitational Particle Production

We study a claimed new mechanism for particle production and black hole evaporation through a spatially dependent temperature. This new temperature is comparable to the Hawking result near the black hole, but is very small far away, and therefore could be a small correction. Here we apply the proposed reasoning to the case of de Sitter space, finding that it over predicts the de Sitter temperature of a minimally coupled scalar by factor of $\approx 4.3$ and over predicts the particle production rate by a factor of $\approx 52$. For non-minimally coupled scalars, it has other various problems; it predicts a negative particle production for conformal, or nearly conformal, coupled scalars; it predicts unsuppressed productions of heavy scalars. This all demonstrates an inconsistency in the proposed formalism.

gr-qc↗

arXiv2025

The Adaptive Communication Framework (ACF) for Extraterrestrial Intelligence Discovery

The Vera C. Rubin Observatory's Legacy Survey of Space and Time will increase interstellar object detection rates to one every few months, substantially elevating the probability of identifying objects with characteristics suggesting artificial origin. Despite this imminent capability, no evidence-based crisis communication framework exists for managing potential technosignature discoveries. We present the Adaptive Communication Framework (ACF), a theoretically grounded protocol that integrates crisis communication theories with the SPECtrum of Rhetoric Intelligences model to address diverse cognitive, social and emotional processing styles. Through analysis of communication failures during COVID-19, Fukushima, and asteroid 99942 Apophis (2004 MN4), we identify critical gaps in managing scientific uncertainty under public scrutiny. The ACF provides graduated protocols calibrated to the Loeb Scale for Interstellar Object Significance, offering specific messaging strategies across four rhetoric intelligence channels (Systematic, Practical, Emotional, Creative) for each evidential level group. Recognizing that Artificial Intelligence (AI) systems will mediate public understanding, the framework incorporates safeguards against synthetic media manipulation and algorithmic misinformation through pre-positioned content seeding and deepfake detection protocols. Our theoretical framework reveals that successful communication of paradigm-shifting discoveries requires simultaneous activation of multiple cognitive channels, with messages adapted to cultural contexts and uncertainty levels. This framework provides essential theoretical groundwork for ensuring humanity's potentially most transformative discovery unfolds through understanding rather than chaos.

physics.soc-ph↗

arXiv2025

Laser Interferometer Lunar Antenna (LILA): Advancing the U.S. Priorities in Gravitational-wave and Lunar Science

The Laser Interferometer Lunar Antenna (LILA) is a next-generation gravitational-wave (GW) facility on the Moon. By harnessing the Moon's unique environment, LILA fills a critical observational gap in the mid-band GW spectrum ($0.1 - 10$ Hz) between terrestrial detectors (LIGO, Virgo, KAGRA) and the future space mission LISA. Observations enabled by LILA will fundamentally transform multi-messenger astrophysics and GW probes of fundamental physics. LILA will measure the lunar deep interior better than any existing planetary seismic instruments. The LILA mission is designed for phased development aligned with capabilities of the U.S.'s Commercial Lunar Payload Services and Artemis programs. LILA is a unique collaboration between universities, space industries, U.S. government laboratories, and international partners.

gr-qc↗

arXiv2025

Galactic Trajectories of Interstellar Objects 1I/'Oumuamua, 2I/Borisov, and 3I/Atlas

The first interstellar objects, 1I/`Oumuamua, 2I/Borisov and 3I/ATLAS, were discovered over the past decade. We follow the trajectories of known interstellar objects in the gravitational potential of the Milky Way galaxy to constrain their possible origin. We perform Monte Carlo orbital integrations using 10,000 trajectory ensembles per object to properly account for measurement uncertainties in both object velocities and Solar motion parameters. We implement a Bayesian statistical framework that combines a Rayleigh-like likelihood function with star formation rate priors to infer stellar ages from the maximum vertical excursions ($z_{\text{max}}$) of orbital trajectories. The likelihood function incorporates age-dependent velocity dispersions reflecting the thin-thick disk transition and dynamical heating over galactic history. Our Monte Carlo analysis yields median $z_{\text{max}}$ values of 0.016 $\pm$ 0.002 kpc for 1I/`Oumuamua, 0.121 $\pm$ 0.010 kpc for 2I/Borisov, and 0.480 $\pm$ 0.020 kpc for 3I/ATLAS. The Bayesian age inference indicates that 1I/`Oumuamua originated from a young stellar system (1.0 Gyr, 68\% CI: 0.1-4.1 Gyr), 2I/Borisov from an intermediate-age population (3.8 Gyr, 68\% CI: 1.8-5.9 Gyr), and 3I/ATLAS from an old thick-disk source (9.6 Gyr, 68\% CI: 7.8-10.3 Gyr). These results demonstrate clear age discrimination where smaller vertical excursions correspond to younger stellar origins.

astro-ph.GA↗

arXiv2025

The Loeb Scale: Astronomical Classification of Interstellar Objects

The Vera C. Rubin Observatory is expected to increase interstellar object (ISO) detections from a few over the past decade to potentially one per few months, demanding a systematic classification scheme. We present the Loeb Scale, formally the Interstellar Object Significance Scale (IOSS), a 0-10 classification system extending the proven Torino Scale framework, to address ISOs' unique anomalies, including potential technosignatures. The scale provides quantitative thresholds for natural phenomena (Levels 0-3) and graduated protocols for increasingly anomalous characteristics (Levels 4-7), with Levels 8-10 reserved for confirmed artificial origin. Each level specifies observable criteria and response protocols. We demonstrate the scale's application using 1I/'Oumuamua (Level 4), 2I/Borisov (Level 0), and 3I/ATLAS (Level 4) as test cases. The Loeb Scale provides the astronomical community with a standardized framework for consistent, evidence-based and dynamic evaluation while maintaining scientific rigor across the full spectrum of possibilities as we enter an era of routine ISO encounters.

physics.pop-ph↗

arXiv2025

Detecting dark objects in the Solar System with Gravitational Wave observatories

Dark objects streaming into the solar system can be probed using gravitational wave (GW) experiments through the perturbations that they would induce on the detector test masses. In this work, we study the detectability of the resulting gravitational signal for a number of current and future GW observatories. Dark matter in the form of clumps or primordial black holes with masses in the range $10^7$-$10^{11}\,\rm{g}$ can be detected with the proposed DECIGO experiment.

gr-qc↗

arXiv2025

From Extraterrestrial Microbes to Alien Intelligence: Rebalancing Astronomical Research Priorities

We examine the funding disparity in astronomical research priorities: the Habitable Worlds Observatory is planned to receive over $10 billion over the next two decades whereas extraterrestrial intelligence research receives nearly zero federal funding. This imbalance is in contrast to both scientific value and public interest, as 65% of Americans and 58.2% of surveyed astrobiologists believe extraterrestrial intelligence exists. Empirical psychological research demonstrates that humanity possesses greater resilience toward extraterrestrial contact than historically recognized. Contemporary studies reveal adaptive responses rather than mass panic, conflicting with the rationale for excluding extraterrestrial intelligence research from federal funding since 1993. The response to the recent interstellar object 3I/ATLAS exemplifies consequences of this underinvestment: despite discovery forecasts of a new interstellar object every few months for the coming decade, no funded missions exist to intercept or closely study these visitors from outside the Solar System. We propose establishing a comprehensive research program to explore both biosignatures and technosignatures on interstellar objects. This program would address profound public interest while advancing detection capabilities and enabling potentially transformative discoveries in the search for extraterrestrial life. The systematic exclusion of extraterrestrial intelligence research represents institutional bias rather than scientific limitation, requiring immediate reconsideration of funding priorities.

astro-ph.IM↗

arXiv2025

The deployment of a geomagnetic variometer station as auxiliary instrumentation for the study of Unidentified Aerial Phenomena

Witness reports of Unidentified Aerial Phenomena (UAP) occasionally associate UAP sightings with local electromagnetic interferences, such as spinning magnetic compasses onboard aircraft or sudden malfunctions of mechanical vehicles. These reports have motivated the incorporation of a magnetometer into the instrumentation suite of the Galileo Project (GP), a Harvard-led scientific collaboration whose aim is to collect and analyze multi-sensor data that collectively could help elucidate the nature of UAP. The goal of the GP magnetometry investigation is to identify magnetic anomalies that cannot be readily explained in terms of a natural or human-made origin, and analyze these jointly with the data collected from the other modalities. These include an ensemble of visible and infrared cameras, a broadband acoustic system and a weather-monitoring system. Here, we present GP's first geomagnetic variometer station, deployed at the GP observatory in Colorado, USA. We describe the calibration and deployment of the instrumentation, which consists of a vector magnetometer and its data acquisition system, and the collection and processing of the data. Moreover, we present and discuss examples of the magnetic field data obtained over a period of 6 months, including data recorded during the May 2024 G5 extreme geomagnetic storm. We find that the data meet and even surpass the requirements laid out in GP's Science Traceability Matrix. Key to the evaluation of our data is the proximity of the variometer station to the USGS magnetic observatory in Boulder, Colorado. By comparing the two sets of data, we find that they are of similar quality. Having established the proper functioning of the first GP variometer station, we will use it as the model for variometer stations at future GP observatories.

astro-ph.IM↗