Harvard astrophysicist Avi Loeb stated that the interstellar comet 3I/ATLAS has a mass of more than 50 billion tons. This value represents at least one million times the mass of 1I/Oumuamua, the first interstellar object detected. Loeb questions the likelihood of such a large body arriving in the Solar System so early in third place on the list of known visitors.
The object was discovered in July 2025 by the ATLAS system and reached perihelion on October 29. Recent data indicate non-gravitational acceleration and loss of up to 13% of the original mass. Post-perihelic observations reveal complex jets in multiple directions, with no visible traditional tail.
- Estimated mass: more than 50 billion tons.
- Comparison: million times bigger than Oumuamua.
- Anomalies: possibly artificial jets and absence of expected massive coma.
Trajectory and recent observations
3I/ATLAS follows a hyperbolic orbit, confirming its origin external to the Solar System. It passed close to Mars in October and reached its closest point to the Sun at 1.4 astronomical units. Images from China’s Tianwen-1 probe captured from Mars show clear cometary activity.
Telescopes like Hubble and ground-based observatories have recorded blue glow and sunward jets. ESA’s JUICE probe will analyze the object between November 2nd and 25th. Projections indicate maximum approach to Earth on December 19, at 1.8 astronomical units, without risk of collision.
Artificial origin hypothesis
Loeb argues that 3I/ATLAS jets could result from technological thrusters. Chemical exhaust velocities reach 3 to 5 km/s, ten times higher than the natural ejection of volatiles. Ion thrusters reach 10-50 km/s, reducing mass loss by orders of magnitude.
The scientist lists ten anomalies, including unlikely ecliptic alignment and nickel-free composition. Mass loss required would be minimal with advanced technology, less than 1% of the total. Loeb classifies the object on its own scale, ranging from 4 to 6 in technological possibility.
Chemical composition detected
Spectroscopy reveals the presence of CO2 (87%), CO (9%) and water (4%). Swift Observatory identified hydroxyl (OH), indicative of water. Absence of traditional tail and blue glow suggest ionization or artificial light source.
- Main elements: dominant carbon dioxide.
- Molecules: cyanide and nickel tetracarbonyl, rare in natural comets.
- Activity: Started at 6.4 AU from the Sun.
Monitoring by space agencies
NASA confirms cometary behavior, but coordinates global observation campaign until January 2026. Juno and Juice probes positioned for flybys in 2026. Images from November show complex jet structure, captured by observatories such as R. Naves.
The International Asteroid Warning Network includes the object on its list of priority targets. JWST data updates chemistry, reinforcing classic cometary signatures.
Post-perihelic anomalies
After October 29, 3I/ATLAS exhibited non-gravitational acceleration and a 13% reduction in mass. Images from November 8 reveal network of jets with no predicted massive gas cloud. Loeb suggests definitive test: absence of coma would indicate unnatural propulsion.
Observations indicate increased brightness and bluish color, compatible with a hot engine or CO+ emissions. International network records variations of 20% in brightness since November.
Future study perspectives
The comet reappears in the sky in November, visible in Virgo and Leo before dawn. Magnitude estimated at 12, accessible with medium telescopes. Final departure occurs in 2026, towards Géminis.
Research focuses on interstellar |air chemistry to compare with local comets. Discovery reinforces need for telescopes like Vera Rubin to detect more visitors.
