Astronomers have discovered 3I/ATLAS, an interstellar object that could be the oldest comet ever seen. On July 1, 2025, the ATLAS survey telescope located in Chile, a part of NASA’s WFIRST mission, made an exciting discovery. The extraordinary object was located some 670 million kilometers from the sun at the time of closest approach. All of these 3I/ATLAS findings have enormous implications for the scientific community. These findings upend everything we thought we knew about where comets come from and how old they are.
Upon its discovery, researchers didn’t waste any time getting to work. They performed the observations using the FORS2 instrument on the Very Large Telescope (VLT) only two days later, on 3 July 2025. Based on preliminary estimates, scientists suspect that 3I/ATLAS is not only active but even bigger than its interstellar predecessors, 1I/‘Oumuamua and 2I/Borisov. This is a pretty typical path for a comet blazing through the galaxy with a high inclination. Its trail indicates that it comes from the Milky Way’s “thick disk,” an area populated by older stars.
Discovery and Characteristics
3I/ATLAS’s discovery is a thrilling moment for astronomical inquiry. The distant object was first spotted by the ATLAS survey telescope in Hawaii, during its regular scans of the skies for potentially hazardous asteroids. It darted fast in the air. It was a vibrant place and a 13-minute timelapse showing its movement was the perfect way to exemplify that.
Matthew Hopkins, an astronomer from the University of Oxford, estimates that 3I/ATLAS might be more than 7 billion years old. “All non-interstellar comets such as Halley’s comet formed with our solar system, so are up to 4.5 billion years old,” he explained. “Interstellar visitors have the potential to be far older, and of those known about so far our statistical method suggests that 3I/ATLAS is very likely to be the oldest comet we have ever seen.”
The discovery ignited excitement among researchers. “Rather than the quiet Wednesday I had planned, I woke up to messages like ‘3I!!!!!!!!!!’,” Hopkins remarked, indicating the enthusiasm surrounding this unprecedented find.
Future Observations and Implications
Beyond its arrival, astronomers expect that 3I/ATLAS will be observable through moderately-sized amateur telescopes in late 2025 and early 2026. As the comet approaches the sun, it is expected to heat up, releasing gases that will provide vital data for testing current astrophysical models. Dr. Michele Bannister noted, “We’re in an exciting time: 3I is already showing signs of activity. The gases that may be seen in the future as 3I is heated by the sun will test our model.”
The study detailing these findings, titled “From a Different Star: 3I/ATLAS in the context of the Ōtautahi-Oxford interstellar object population model,” is set to be presented at the Royal Astronomical Society’s National Astronomy Meeting (NAM 2025) in Durham. This presentation is expected to be one of the presentations that attracts the most attention due to the potential impact 3I/ATLAS will have on future astronomical observation.
Broader Context and Significance
Besides being the first-ever nuclear-powered comet, the discovery of 3I/ATLAS will change how scientists think about interstellar objects. Professor Chris Lintott emphasized its significance: “This is an object from a part of the galaxy we’ve never seen up close before.” He further added that “we think there’s a two-thirds chance this comet is older than the solar system, and that it’s been drifting through interstellar space ever since.”
Dr. Rosemary Dorsey expressed her optimism regarding future discoveries made possible by advanced telescopes like the Vera C. Rubin Observatory. “The solar system science community was already excited about the potential discoveries Rubin will make in the next 10 years, including an unprecedented number of interstellar objects,” she stated.