The telescope is one of five around the world that are part of the Asteroid Terrestrial-impact Last Alert System, or ATLAS, which is a NASA-funded project that watches for space rocks that might be on a collision course with our planet. The observation was submitted to the International Astronomical Union’s Minor Planet Centre, which maintains a catalogue of small space bodies in the solar system. Other sky watchers quickly took a look. “Follow-up observations on July 1 and 2 began to reveal that its orbit might be unusual, possibly interstellar,” said Larry Denneau, a co-principal investigator for ATLAS, which was developed by the University of Hawaii. Then, an amateur astronomer, Sam Deen, spotted A11pI3Z in photos taken by ATLAS in late June. The additional sightings allowed more precise calculations of the trajectory.