A11pl3Z confirmed as third interstellar object, Mars flyby expected in October 2025
A new interstellar object, provisionally named A11pl3Z and approximately 20 km (12 miles) wide, has been confirmed as only the third known visitor from another star system to enter the Solar System.
Interstellar object A11pl3Z orbit diagram July 2, 2025. Credit: Catalina Sky Survey, The Watchers
A11pl3Z was first observed entering the Solar System on June 14, 2025, by NASA’s Asteroid Terrestrial-impact Last Alert System (ATLAS). The object measures approximately 20 km (12 miles) in diameter and traveling at a velocity of 66 km/s (237 600 km/h, or 147 637 mph). Early analyses indicate an eccentricity of about 6, strongly confirming its interstellar origin.
This object is only the third known interstellar visitor recorded passing through the Solar System, following ‘Oumuamua in October 2017 and comet Borisov in August 2019, making it a priority observation target. Professional and amateur astronomers are expected to closely monitor A11pl3Z as it remains observable for several months.
Based on preliminary orbit calculations, A11pl3Z will traverse the inner Solar System, passing between Earth’s and Mars’ orbits in October 2025.
Following its perihelion passage, the object’s trajectory will redirect it out of the Solar System and back into interstellar space.
Teo Blašković founded The Watchers in 2011 and edited it until 2026, covering seismic and volcanic activity, extreme weather, space weather and near-Earth objects. Articles on this page are his archive.
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