The interstellar comet 3I/ATLAS, discovered in July 2025, surprised astronomers by remaining intact after passing through perihelion, the closest point to the Sun, on October 30. Images captured by the Nordic Optical Telescope on November 11 show that the object has maintained its structure and continues to release materials, defying predictions of fragmentation. The MeerKAT radio telescope in South Africa detected radio signals on October 24, an unprecedented feat for a celestial body formed outside the Solar System. The discovery reinforces scientific interest in the comet, which is expected to pass close to Jupiter in March 2026.
Detected by the ATLAS telescope in Chile, 3I/ATLAS is the third interstellar object identified, after 1I/’Oumuamua and 2I/Borisov. Its hyperbolic trajectory indicates that it is not tied to solar gravity. Studies by the James Webb Space Telescope revealed a composition rich in carbon dioxide, unusual for comets. The object travels at more than 210,000 km/h and poses no risk to Earth.
- Composition: High concentration of CO₂, eight times greater than that of water.
- Size: Core estimated between 320 meters and 5.6 kilometers.
- Trajectory: It will pass within 50 million kilometers of Jupiter in 2026.
Peculiar chemical composition
Observations by James Webb indicate that 3I/ATLAS has a coma dominated by carbon dioxide, with a ratio of 7.6 to 1 in relation to water. This feature suggests formation in cold regions of another star system.
Exposure to cosmic rays over billions of years may have altered its surface, creating a dark crust up to 20 meters high, according to a study published on arXiv.
New radio signals
The MeerKAT radio telescope has detected hydroxyl radical absorption lines at frequencies of 1.665 GHz and 1.667 GHz.
This detection, made after unsuccessful attempts in September, confirms the sublimation of ice on the comet.
NASA’s Juno probe will attempt to capture new waves between 40 and 50 MHz during its passage by Jupiter.
Surprising resistance
Images from the Nordic Optical Telescope show a growing ionic tail, indicating intense activity.
The comet did not fragment at perihelion, contradicting models that predicted disintegration through sublimation.
Avi Loeb, a former Harvard astronomer, suggests an unnatural mechanism, but the hypothesis lacks evidence.
The scientific community considers the behavior typical of an interstellar comet.
Next research steps
NASA and ESA plan detailed observations in December 2025, when the comet will be 270 million kilometers from Earth. ESA’s JUICE probe will carry out analyzes between December 2nd and 25th.
The Virtual Telescope Project in Italy will continue to monitor the ionic tail, which has gained brightness and structure.
Origin debate
Avi Loeb hypothesized that 3I/ATLAS could be a technological artifact, but scientists like David Jewitt, from UCLA, claim that all observations point to a natural comet. The detection of radio signals reinforces this view, ruling out artificial origin.
Trajectory and behavior
The comet follows a hyperbolic orbit, with a speed of 58 km/s as it enters the Solar System. After perihelion, its hue changed to bluish, an effect of ice sublimation. The next approach to Earth, on December 19, will allow new studies with the Hubble and James Webb telescopes, which will look for signs of changes in the comet’s structure.
