The New Astronomical Frontier of Interstellar Objects

Abstract

The upcoming commencement of the Vera C. Rubin Observatory's Legacy Survey of Space of Time (LSST) will greatly enhance the discovery rate of interstellar objects (ISOs). `Oumuamua and Borisov were the first two ISOs confirmed in the Solar system, although the first interstellar meteor may have been discovered earlier. We discuss the properties of `Oumuamua and Borisov and explore the expected abundance of ISOs as a function of size in the solar neighborhood. We compare the expected abundance of ISOs to that of objects in the Oort cloud, and draw conclusions about the mass budget per star that is required to produce ISOs. We also investigate the possibility of ISOs being captured into bound orbits within the solar system, both from its birth star cluster and in the field. We examine the potential for ISOs to transport prebiotic or biotic material between planetary systems. We consider signatures of ISOs colliding with the Earth, the Moon, and neutron stars, as well as the possibility of differentiating ISOs from solar system objects in stellar occultation surveys. Finally, we discuss advantages that the imminent advent of LSST will afford the field of ISO studies, including large-number statistics that will reveal the origins of ISOs and discoveries of rare ISOs providing insights into exotic phenomena. One of the two branches of the newly established Galileo Project seeks to learn more about the nature of ISOs like `Oumuamua by performing new searches and designing follow-up observations.