Predating the solar system and from an unexplored area: what the oldest comet ever detected looks like
The ATLAS telescope in Chile was responsible for identifying this celestial body, a discovery that mobilized scientific teams from several continents to reveal unprecedented data on the early evolution of the galaxy and the formation of planetary systems.
Unexpected wonders continue to arrive from deep space, inviting us to gaze at the heavens with renewed awe. The recent discovery of 3I/ATLAS has generated global excitement among astronomers and opens a unique window into the galaxy's distant past.
Identified on July 1, 2025, by the ATLAS telescope in Chile, 3I/ATLAS becomes the third interstellar object discovered in the history of the Solar System and, according to preliminary analyses, possibly the oldest comet detected to date . Its entry into the solar neighborhood triggered an unprecedented international scientific response.
A detection that mobilized the world
The discovery was made possible thanks to the ATLAS survey's automated network of telescopes, designed to identify moving objects. On July 1, the Chilean telescope detected a body 670 million kilometers from the Sun. The news spread quickly, triggering collaboration between observatories and scientific teams around the world.
The response was immediate: Oxford University, Michigan State University (MSU), the European Southern Observatory, NASA's Jet Propulsion Laboratory, the University of Hawaii , and other institutions joined the study. ATLAS member Larry Denneau celebrated the detection: "It's especially gratifying to have found it in the direction of the galactic center, a difficult place to observe," he told MSU Today.
Karen Meech of the University of Hawaii reported that resources such as the Southern Astrophysical Research Telescope and the Gemini Observatory were activated to capture images and data of the comet in its early stages. This cooperation was key to obtaining light spectra and details about its brightness, position, and composition.
An ancient visitor, swift and on the run
Initial data describe 3I/ATLAS as an interstellar object with a hyperbolic orbit , a trajectory that will take it forever away from the solar system. It travels at about 60 kilometers per second relative to the Sun. This "boomerang-shaped" trajectory differentiates it from most known comets, which orbit the Sun in an elliptical fashion.
Images captured by the Canada-France-Hawaii Telescope and the Very Large Telescope show a compact coma, the cloud of gas and dust that characterizes active comets. According to Darryl Seligman, a researcher involved in the discovery, the low variation in its brightness suggests a stable rotation or sustained cometary activity : “It probably contains ices, especially subsurface, and those ices can become active as it gets closer to the Sun ,” he explained.
What's most striking is its estimated age. Matthew Hopkins of Oxford University stated during the 2025 National Astronomy Meeting that " 3I/ATLAS is very likely the oldest comet we've ever seen."
It's estimated to be more than seven billion years old and comes from the thick disk of the Milky Way, a region of ancient stars. Chris Lintott, also from Oxford, reinforced this idea: "We think there's a two-thirds chance this comet is older than the solar system."
Recent studies have supported these estimates. Researchers led by Hopkins and Seligman published two detailed analyses of the comet's behavior and origin. The first study focused on its trajectory and physical properties. The second explored its age and ties to the Milky Way's thick disk.
Unlike the other two known interstellar objects—1I/'Oumuamua (2017) and 2I/Borisov (2019) —3I/ATLAS may have originated in a galactic region never before observed up close. “This is an object from a part of the Galaxy we’ve never seen up close,” Lintott noted.
Technology, cooperation and future opportunities
Beyond its age or history, the discovery stands out for the magnitude of the scientific collaboration surrounding it. “We have data coming in from all over the world on this object,” Seligman remarked. Space institutions from the Americas, Europe, and Oceania, the European Space Agency, NASA, and research centers from Canada, Chile, and Australia participated in the monitoring.
Furthermore, 3I/ATLAS's behavior has allowed galactic models to be validated. Hopkins and his Oxford team had developed a predictive model—Ōtautahi-Oxford—using data from the Gaia satellite and simulations, and 3I/ATLAS matched their predictions. "It's a fantastic opportunity to test our model against something completely new and possibly old ," Hopkins explained to the Royal Astronomical Society.
With the Vera C. Rubin Observatory about to begin operations, a new era in the detection of interstellar objects is anticipated. In parallel, 3I/ATLAS will be monitored by telescopes such as the James Webb and Hubble telescopes, and a possible space mission to study it up close is being evaluated.
This global collaboration, along with photometric and spectroscopic missions, could reveal key insights into the formation of stars, planets, and the early evolution of the Galaxy.
Unexpected wonders continue to arrive from deep space, inviting us to gaze at the heavens with renewed awe. The recent discovery of 3I/ATLAS has generated global excitement among astronomers and opens a unique window into the galaxy's distant past.
Identified on July 1, 2025, by the ATLAS telescope in Chile, 3I/ATLAS becomes the third interstellar object discovered in the history of the Solar System and, according to preliminary analyses, possibly the oldest comet detected to date . Its entry into the solar neighborhood triggered an unprecedented international scientific response.
A detection that mobilized the world
The discovery was made possible thanks to the ATLAS survey's automated network of telescopes, designed to identify moving objects. On July 1, the Chilean telescope detected a body 670 million kilometers from the Sun. The news spread quickly, triggering collaboration between observatories and scientific teams around the world.
The response was immediate: Oxford University, Michigan State University (MSU), the European Southern Observatory, NASA's Jet Propulsion Laboratory, the University of Hawaii , and other institutions joined the study. ATLAS member Larry Denneau celebrated the detection: "It's especially gratifying to have found it in the direction of the galactic center, a difficult place to observe," he told MSU Today.
Karen Meech of the University of Hawaii reported that resources such as the Southern Astrophysical Research Telescope and the Gemini Observatory were activated to capture images and data of the comet in its early stages. This cooperation was key to obtaining light spectra and details about its brightness, position, and composition.
An ancient visitor, swift and on the run
Initial data describe 3I/ATLAS as an interstellar object with a hyperbolic orbit , a trajectory that will take it forever away from the solar system. It travels at about 60 kilometers per second relative to the Sun. This "boomerang-shaped" trajectory differentiates it from most known comets, which orbit the Sun in an elliptical fashion.
Images captured by the Canada-France-Hawaii Telescope and the Very Large Telescope show a compact coma, the cloud of gas and dust that characterizes active comets. According to Darryl Seligman, a researcher involved in the discovery, the low variation in its brightness suggests a stable rotation or sustained cometary activity : “It probably contains ices, especially subsurface, and those ices can become active as it gets closer to the Sun ,” he explained.
What's most striking is its estimated age. Matthew Hopkins of Oxford University stated during the 2025 National Astronomy Meeting that " 3I/ATLAS is very likely the oldest comet we've ever seen."
It's estimated to be more than seven billion years old and comes from the thick disk of the Milky Way, a region of ancient stars. Chris Lintott, also from Oxford, reinforced this idea: "We think there's a two-thirds chance this comet is older than the solar system."
Recent studies have supported these estimates. Researchers led by Hopkins and Seligman published two detailed analyses of the comet's behavior and origin. The first study focused on its trajectory and physical properties. The second explored its age and ties to the Milky Way's thick disk.
Unlike the other two known interstellar objects—1I/'Oumuamua (2017) and 2I/Borisov (2019) —3I/ATLAS may have originated in a galactic region never before observed up close. “This is an object from a part of the Galaxy we’ve never seen up close,” Lintott noted.
Technology, cooperation and future opportunities
Beyond its age or history, the discovery stands out for the magnitude of the scientific collaboration surrounding it. “We have data coming in from all over the world on this object,” Seligman remarked. Space institutions from the Americas, Europe, and Oceania, the European Space Agency, NASA, and research centers from Canada, Chile, and Australia participated in the monitoring.
Furthermore, 3I/ATLAS's behavior has allowed galactic models to be validated. Hopkins and his Oxford team had developed a predictive model—Ōtautahi-Oxford—using data from the Gaia satellite and simulations, and 3I/ATLAS matched their predictions. "It's a fantastic opportunity to test our model against something completely new and possibly old ," Hopkins explained to the Royal Astronomical Society.
With the Vera C. Rubin Observatory about to begin operations, a new era in the detection of interstellar objects is anticipated. In parallel, 3I/ATLAS will be monitored by telescopes such as the James Webb and Hubble telescopes, and a possible space mission to study it up close is being evaluated.
This global collaboration, along with photometric and spectroscopic missions, could reveal key insights into the formation of stars, planets, and the early evolution of the Galaxy.