- 3I/ATLAS is only the third known interstellar object detected passing through our Solar System, discovered on 1 July 2025 by the ATLAS telescope in Chile.
- This comet showcases unusual activity and composition, including high levels of carbon dioxide and a rare tail and coma structure captured by instruments on Mars and space telescopes such as Hubble and JWST.
- It is estimated to be older than our Solar System, likely formed in the thick disk of the Milky Way, distinguishing it from objects originating within the Solar System.
- ESA and NASA missions, including Hubble, Webb, Mars Express, and Juice, are conducting detailed observations to uncover its trajectory, composition, and potential clues about planetary system formation beyond our Solar System.
Out of the vastness of space, a celestial messenger from beyond our Sun has streaked into our cosmic neighborhood — comet 3I/ATLAS. Its name might sound like a string of astrophysical jargon, but behind it lies one of the most extraordinary astronomical discoveries in recent history. In 2025, this icy traveler became only the third confirmed interstellar object to be detected crossing our Solar System, after the enigmatic 1I/ʻOumuamua and the dusty, comet-like 2I/Borisov.
With a speed that defies gravitational capture and a makeup that holds clues to ancient planetary systems, 3I/ATLAS has captivated the world’s leading space agencies, observatories, and citizen astronomers alike. From its discovery and naming to the inspiring observations gathered by ESA and NASA, every detail deepens our understanding of the landscapes beyond our Sun’s grasp. It’s a story of icy gases, space telescope collaborations, forgotten precovery images, and the possibility that comets like this could be older than Earth itself.
What Is Comet 3I/ATLAS?
Comet 3I/ATLAS, officially designated C/2025 N1 (ATLAS), is an interstellar comet currently passing through our Solar System.
Identified on July 1, 2025, by the Asteroid Terrestrial-impact Last Alert System (ATLAS) stationed at Río Hurtado, Chile, it has stunned astronomers with its unmistakably interstellar trajectory and hyperbolic speed. What makes this object so rare is that, unlike the thousands of comets catalogued before it, this one wasn’t born in our solar nursery. It is a guest from the greater galaxy, never to return.
Its extremely hyperbolic orbit, with an eccentricity of 6.1373, is far beyond that of typical Solar System comets, solidifying its status as an object from beyond the gravitational influence of our Sun. It’s fast — blazing past the inner planets at over 210,000 km/h (about 58 km/s in velocity relative to the Sun).
How 3I/ATLAS Got Its Name
The name ‘3I/ATLAS’ follows a specific convention used by the International Astronomical Union (IAU). The ‘3I’ designation signals that it’s the third confirmed ‘Interstellar’ object — following 1I/ʻOumuamua and 2I/Borisov. ‘ATLAS’ credits the discovery telescope and the survey project operated by the University of Hawaii and funded by NASA to scan the sky for potential incoming threats or celestial oddities.
Before getting its official name, it went by a quirky temporary title: A11pl3Z. This code was generated during early tracking efforts and later superseded by the more lasting and meaningful 3I/ATLAS label.
Trajectory and Orbital Highlights
3I/ATLAS follows a retrograde and highly inclined orbit of 175.11° relative to the ecliptic, the plane on which most planets orbit. Having entered the Solar System from the direction of the constellation Sagittarius, close to the Milky Way’s core, it showcases one of the steepest approach angles encountered.
The comet made its closest approach to the Sun (perihelion) on 29 October 2025, coming within 1.36 AU — about 203 million kilometers, or between the orbits of Earth and Mars. It previously skirted Mars at a distance of just 0.19 AU (approximately 28 million km) on 3 October 2025 and will pass about 0.36 AU from Jupiter on 16 March 2026.
What Makes 3I/ATLAS Special?
Unlike its forebear 1I/ʻOumuamua, which remained non-luminous and sparked controversial theories about its nature, 3I/ATLAS has revealed classic signs of cometary activity.
It sports an enlarged coma (a halo of gas and mineral particles) and multiple tails that reflect light and stretch across hundreds of thousands of kilometers. Imaging attempts from Earth and from orbit confirm these structures. Some of these tails resemble those observed in long-period Solar System comets, while others emanate toward the Sun due to vaporizing materials on the sunlit side.
Its speed places it as the fastest of the interstellar trio, with a heliocentric hyperbolic excess speed (v∞) estimated at 58 km/s.
This interstellar comet represents a unique opportunity to explore the mysteries of distant planetary systems. Its extraordinary speed, composition, and origin provide valuable data amid the enigma of interstellar travelers. As it moves away from our system, astronomers will continue to monitor its fading light and extract secrets from the observational data it leaves in its wake.