Extraterrestrial: The First Sign of Intelligent Life Beyond Earth

by Avi Loeb

Either way, ‘Oumuamua was a rarity. If it was elongated, we had never seen any naturally occurring space object that size and that elongated; if it was flat, we had never seen any naturally occurring space object that size and that flat. Consider, for context, that all asteroids previously seen in the solar system had length-to-width ratios of, at most, three. ‘Oumuamua’s, as I have just noted, was somewhere between five and ten. And there was more. In addition to being small and oddly shaped, ‘Oumuamua was strangely luminous. Despite its diminutive size, as it passed the Sun and reflected the Sun’s light, ‘Oumuamua proved to be relatively bright, at least ten times more reflective than typical solar system asteroids or comets. If, as seems possible, ‘Oumuamua was a few times smaller than the upper limit of a few hundred yards that scientists presumed it to be, its reflectivity would approach unprecedented values—levels of brightness similar to a shiny metal.