Potential interstellar bodies are now observed zipping through our solar system, and both amateur and professional astronomers globally are racing to direct telescopes towards these phenomena, refine their trajectory models, and ultimately validate their status as visitors from another star.

The object provisionally named A11PL3Z represents the third interstellar entity detected to date. The asteroid ‘Oumuamua was first seen in October 2017, just three days after it passed closest to Earth, and its unusual acceleration sparked a variety of hypotheses, including the possibility of it being an alien spacecraft. The second identified object, Comet Borisov, was observed in 2019, allowing for closer examination given its early passage through the solar system.

A11PL3Z was first identified by the Deep Random Survey in Chile, a group of amateur astronomers. However, a review of earlier observations by other teams revealed that it was initially spotted on June 14 by NASA’s Asteroid Terrestrial-impact Last Alert System (ATLAS). It is estimated to measure approximately 20 km in width and is currently traveling at around 66 km/s, accelerating as it gets pulled in by solar gravity. In October, it will reach its closest point to the Sun, passing within two astronomical units (the Earth is twice the distance from the Sun) before swinging away and exiting the solar system.

This provides a limited window for studying A11PL3Z, though it’s more than that available for previous interstellar objects, which were seen hurtling towards the solar system. “These objects move through the solar system at incredible speeds,” remarks Mark Norris from the University of Central Lancashire. “They are quite transient, which restricts our ability to learn about them.”

Sadly, the prospect of sending missions to intercept and study A11PL3Z is beyond the reach of current technology, notes Norris. “If we were to launch a mission today, it would be too late,” he states. However, the European Space Agency (ESA) is planning a comet interceptor mission set for launch in 2029, which would remain in space to await the arrival of newly discovered comets and possibly interstellar objects.

For the time being, astronomers are relying on existing telescopes to observe A11PL3Z from a distance. “We anticipate we will be observing it by the end of the year, giving us ample time to prepare our spectrometers once we finalize the trajectory,” shares Richard Moisle. When will our observers discern its visibility? There’s a palpable excitement as everyone is prepared and looking forward to this opportunity.

At the time of this writing, over 100 observations of A11PL3Z have already been logged, and the Minor Planet Center—the official body responsible for monitoring and reporting such celestial entities—is expected to confirm its interstellar classification later today.