The Inferred Abundance of Interstellar Objects of Technological Origin
However, assuming random directions of interstellar objects does not apply if the objects are artificial and directed towards regions of interest, such as the habitable zones of stars. Estimating the frequency and density of interstellar objects given they are targeted requires considering the quantity of targets and volume of targeted regions.
By applying the Copernican Principle, which suggests that human civilization on Earth is a typical example of the emergence of intelligent life in the universe, we gain insights into possible targets of extraterrestrial technological artifacts (ETAs). The traditional Search for Extraterrestrial Intelligence (SETI), focused on electromagnetic signals [7] which escape the Milky Way galaxy and cannot be detected a light-crossing time after transmission ceases. Indeed, one of the critical parameters in the Drake equation is the lifetime of a transmitting civilization [8]. However, spacecraft propelled by chemical propellants do not exceed the local escape speed for the Milky-Way galaxy, remain gravitationally bound to it and accumulate over time summing over the rise and fall of space-venturing civilizations.
In this paper, we develop a model for calculating the total number of interstellar objects of technological origin bound by the galactic thin disk based on observational data, and we find that the quantity of objects is significantly reduced if the objects’ trajectories are targeted. The outline of the paper is as follows. In Section 2 we calculate the expected velocities of interstellar objects given their launch characteristics. In Section 3, we calculate the local density and total quantity of interstellar objects bound to the Milky-Way given our detection rates. In Section 4, we consider the implications for the previously detected interstellar objects.
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Conclusions
The abundance of ISOs depends on their size and can be calibrated through future surveys such as the Legacy Survey of Space and Time (LSST) on the Vera C. Rubin Observatory in Chile.1 Data from the James Webb Space Telescope may identify the nature and 3D trajectory of more ’Oumuamua-like or other interstellar objects crossing through or trapped within the solar system [6, 20].
The Galileo Project2 was established in 2021 [21] as a scientific search for potential astro-archaeological artifacts from ETCs, including anomalous interstellar objects that may be revealed by the Webb telescope of Vera C. Rubin Observatory. The Galileo Project will also search for Unidentified Aerial Phenomena (UAP) within the atmosphere of the Earth [21]. As objects of interstellar origin are discovered by the Galileo Project, number density estimates can be improved based on detection rates. If extraterrestrial equipment is discovered in a survey of space, we can estimate the total quantity of such objects conditional on whether they are defunct space debris or functional probes.
Furthermore, the quantity of ISOs allows for calculations of the necessary mass budget per star to produce the objects. If interstellar objects originate in protoplanetary disks, our estimates for quantity can place further constraints on the fraction of mass that disks must eject to achieve the given population of objects [22]. Analysis of ISOs can also provide insights into rare or unexpected phenomena, including an unusual material composition or whether they may transport prebiotic or biotic materials across interstellar distances [23]. The expedition planned by the Galileo Project to retrieve the interstellar fragments from CNEOS 2014-01-08 will be able to provide more insights into its rare material strength, isotope abundances, and nature [24].
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