Introduction: A new era of cosmic visitors
Over the last eight years, humanity has been visited not by missions or probes, but by a trio of interstellar objects that burned bright in the sky and baffled scientists. Oumuamua, 2I/Borisov, and 3I/ATLAS are not mere curiosities. They are empirical jolts to our understanding of how planets and comets form around stars. Each object arrived with a different composition, trajectory, and history, forcing researchers to rethink the textbook narratives of planetary birth and icy outer world chemistry.
Oumuamua: The first interstellar messenger
Oumuamua arrived in 2017 as the inaugural confirmed interstellar visitor. Its name, derived from Hawaiian, means “a messenger from afar arriving first.” Physically, it was unlike any known Solar System body: a reddish, elongated rock that looked more like a cigar than a typical comet. Most perplexingly, it showed non-gravitational acceleration as it moved away from the Sun, despite lacking a visible coma or tail. The object’s origin remains a mystery, with theories ranging from an unusual ejection from another star system to remnants of ancient, alien architectures—though the latter remains speculative. Its telltale absence of a traditional cometary atmosphere challenged assumptions about what interstellar visitors should look like and how they should behave.
