3I/ATLAS, the third known interstellar object to cross our Solar System, was first spotted on 1 July 2025 and immediately became a magnet for speculation. It was discovered by the Asteroid Terrestrial-impact Last Alert System (ATLAS) survey in Hawaii and was quickly confirmed to be unbound to the Sun, meaning it had arrived from outside our planetary neighbourhood.
Some researchers, including Harvard astrophysicist Avi Loeb, argued that scientists should at least consider whether such visitors might be technological probes rather than ordinary chunks of rock and ice. Others pushed back, warning that talk of 'alien spacecraft' risked overshadowing the hard‑won data and that the priority should be careful measurement rather than sensational claims. That debate helped propel 3I/ATLAS to the top of the observing agenda as it sped towards the inner Solar System.
