Lead: Astronomers using the Gemini South telescope in Chile reported on Sept. 5, 2025 that the interstellar comet 3I-Atlas is developing an increasingly prominent dust and gas tail as it moves inward; the object was about 238 million miles (384 million kilometers) from Earth and is due to pass closest to the sun in late October and nearest to Earth in December at roughly 167 million miles (269 million kilometers).
Key Takeaways
- Gemini South images from late August/early September show a widening coma and a longer tail on comet 3I-Atlas.
- NOIRLab scientists say the object is becoming more active as it approaches the inner solar system.
- As of early September 2025, the comet lay ~238 million miles (384 million km) from Earth.
- 3I-Atlas will reach perihelion at the end of October 2025, then pass about 167 million miles (269 million km) from Earth in December.
- This is the third confirmed interstellar object observed in our solar system to date.
Verified Facts
High-resolution images released by the Gemini South observatory in Chile show a clear dust-and-gas envelope (coma) around 3I-Atlas and a tail that is longer than in earlier photos. The observations were released by NOIRLab, which operates the Gemini South telescope.
NOIRLab and other teams report that the comet’s activity — the release of dust and gas driven by solar heating — has increased as it approaches the sun. Increased activity produces both a brighter coma and a more extended tail visible in optical images.
Distance and timing data from NASA indicate the comet was about 238 million miles (384 million kilometers) from Earth at the start of September 2025. It will reach its closest point to the sun at the end of October 2025, then make its nearest Earth approach in December 2025 at about 167 million miles (269 million kilometers), a distance greater than that between Earth and the sun.
3I-Atlas is categorized as an interstellar object because its inbound trajectory and measured velocity indicate an origin beyond our solar system. To date, it is the third such object confirmed by the astronomical community.
Context & Impact
Interstellar visitors like 3I-Atlas provide rare opportunities to sample material formed around other stars. Even remote imaging and spectroscopic observations can reveal composition, dust production rates, and how these properties compare with native solar system comets.
Although brightening and tail growth attract public and scientific interest, the object’s trajectory poses no threat to Earth. Its closest approach distances place it well outside collision risk and largely beyond easy reach for spacecraft interception.
Ongoing monitoring by ground-based observatories and space telescopes will track changes in activity through perihelion and the December approach, helping scientists refine models of volatile loss and dust dynamics in interstellar bodies.
New Gemini South images show increased activity and a more extended tail as the comet moves inward, confirming it has become more active than in earlier observations.
NOIRLab (National Science Foundation)
Unconfirmed
- Precise nucleus size and shape remain uncertain pending higher-resolution imaging or radar data.
- Detailed chemical composition beyond broad dust/gas signatures has not yet been fully determined.
- Exact origin region in another star system is not identified and remains speculative.
Bottom Line
Gemini South’s recent images show 3I-Atlas growing more active and developing a more prominent tail as it approaches the sun. While it poses no hazard to Earth, continued observations through late 2025 will be important to compare this interstellar visitor’s properties with those of known solar system comets.