Interstellar comet 3I/ATLAS reached perihelion this Wednesday, October 29, 2025, at 1.36 astronomical units from the Sun, equivalent to 204 million kilometers.
Discovered on July 1, 2025, by the ATLAS telescope in Chile, the object follows a hyperbolic orbit with a speed of 58 km/s, confirming its origin outside the Solar System.
Astronomers from NASA and ESA coordinate observations to analyze activity under intense solar radiation.
Main observatories in action
Telescopes in Hawaii and Chile capture daily data from the coma and tail.
- Nordic Optical Telescope records CO₂ jets and fine dust.
- Hubble and James Webb identify spectra with nickel and cyanide.
This collaboration ensures continuous monitoring despite solar conjunction. Preliminary observations show accelerated sublimation of volatile ices, without total fragmentation so far.
Hyperbolic trajectory in detail
The orbit of 3I/ATLAS has an eccentricity greater than 5, higher than that of ‘Oumuamua and Borisov.
Maximum speed of 68 km/s at perihelion propels exit from the Solar System.
It will pass Venus on November 3 at 97 million km and Earth on December 19 at 269 million km. No collision risk with planets was detected by orbital simulations.
Chemical composition reveals distant origins
Spectroscopic analyses expose differences
Spectra indicate low water presence and high carbon dioxide in the coma.
Extreme negative polarization suggests fine dust exposed to interstellar radiation for millions of years. JWST data confirm rare organic molecules, absent in common solar comets.
Post-perihelion monitoring intensified
Ground-based telescopes resume sightings in November to assess nucleus integrity.
ESA’s Juice probe plans images in December during departure. Luminosity variations at magnitude 11.5 will allow detection by amateur equipment.
Jets and ejections under scrutiny
Dust production increase follows power law rH^(-3.8), standard in active comets.
Absence of outbursts indicates initial structural stability. Future observations will focus on possible debris trails. Fragments, if they occur, will form detectable tracks by sky surveys.
Upcoming planetary passages
In March 2026, 3I/ATLAS will cross Jupiter’s orbit at 54 million km. Gravitational interactions will be recorded by NASA’s Juno.
These events provide data on dynamics of interstellar objects. The study contributes to models of formation in exoplanetary systems.
