Astronomers from NASA and the European Space Agency recorded the interstellar comet 3I/ATLAS reaching perihelion on October 29, 2025. The object, originating from another star system, passed 203 million kilometers from the Sun.
The proximity generated accelerated release of gases and dust due to the intense heat. Observations indicate fissures in the core less than 1 kilometer in diameter.
The event occurred because thermal and gravitational forces act on the composition rich in volatile ices.
- Maximum speed reached: 68 km/s.
- Minimum distance to Earth: 270 million kilometers.
- Composition detected: carbon dioxide and metals such as nickel.
Initial discovery and confirmation
The ATLAS telescope in Chile detected 3I/ATLAS on July 1, 2025.
Hyperbolic trajectory confirmed interstellar origin.
Pre-discoveries date back to May 2025 via NASA’s TESS satellite.
Signs of core instability
Hubble Space Telescope observations revealed reddish coma in July 2025.
Gas jets increased in September.
Nucleus exhibits extreme negative polarization.
In October, ice sublimation accelerated to 770 watts per square meter.
Monitoring by space agencies
NASA coordinates tracking with SOHO and GOES-19.
ESA uses Juice for observations in November 2025.
Data arrives in February 2026.
- Instruments involved: LASCO C2 and CCOR-1 coronagraph.
- Collaboration: observatories in Hawaii and Chile.
Chemical composition revealed
Spectroscopic analyzes identify CO2 eight times higher than in local comets.
Water ice detected 450 million kilometers from the Sun.
Vaporized nickel causes unusual shine.
Absence of heavy metals suggests formation in ancient stars.
Anomalous acceleration detected
NASA’s Davide Farnocchia measured acceleration beyond solar gravity.
Components: anti-Sun and lateral direction.
Estimated mass loss: 2 million tons.
Coronal mass ejection effect
On September 24, 2025, CME collided with the tail.
Ion tail has temporarily disconnected.
Coma expanded to 300 thousand kilometers in diameter.
Brightness increased to magnitude 9.
Post-perihelion trajectory
Passage of Venus on November 3, 2025 at 97 million kilometers.
Approach to Earth on December 19, 2025.
Encounter with Jupiter on March 16, 2026 at 54 million kilometers.
Space probe observations
Europe Clipper crosses Ion tail between October 30 and November 6, 2025.
Hera collects data during transit.
Juno records images in March 2026.
Differences with previous comets
Compared to 1I/ʻOumuamua, it has a visible coma and tail.
Different from 2I/Borisov, more massive core: 33 billion tons.
Orbital eccentricity: greater than 6.
Preparation for sharding
Models predict total disruption in 2026.
Debris will form dust trail.
Meteor risk: minimal for Earth.
Intensification of observations
IAWN Campaign from November 27, 2025 to January 27, 2026.
Vera C. Rubin Telescope begins astrometry on November 27.
Focus on OH and dust emissions.
Future Earth Visibility
Reappears on November 11, 2025 before dawn.
Magnitude 10-12 in Virgo and Leo.
Picco in December 2025.
Preliminary brightness data
Color photometry shows dominant blue tone.
Gases contribute to 50% of visible brightness.
Contrasts with expected reddish dust.
Expanded international collaboration
Teams from the Canarias Astrophysics Institute contribute.
Australian researchers model sublimation.
IAC analyzes use TWIN telescope.
Chronology of key events
- May 7, 2025: Initial activity detected by TESS.
- July 1, 2025: official discovery.
- October 3, 2025: Mars flyby at 29 million kilometers.
- October 29, 2025: perihelion.
- 2026: exit from the solar system towards Zeta Geminorum.
Future analysis perspectives
James Webb detects rare organic molecules.
SPHEREx studies properties of ice.
