The interstellar comet 3I/ATLAS became visible again from Earth after its passage through perihelion, on October 29, 2025, 1.4 astronomical units from the Sun. Captured by the Lowell Observatory in Arizona, the object displays an unusual bluish glow, according to a study published on the arXiv platform. Astronomers point out that its chemical composition, rich in carbon dioxide, defies known models. The scientific community intensifies observations to understand its origin.
The comet, discovered in July 2025 by the ATLAS telescope in Chile, is the third interstellar object identified. It follows a hyperbolic trajectory, with speeds exceeding 210,000 km/h, indicating origins outside the Solar System. Its passage sparks interest in possible clues about the formation of the universe. Amateur telescopes can now detect it in the Northern Hemisphere.
- Speed: 210 thousand km/h, in hyperbolic orbit.
- Composition: Predominance of CO₂, eight times more than water.
- Origin: Estimated at 7 billion years, older than the Solar System.
- Observation: Visible with telescopes after sunrise, in the constellation Virgo.
New image after perihelion
Qicheng Zhang, a researcher at Lowell Observatory, captured the first post-perihelion optical image of 3I/ATLAS on October 31. The photo reveals a diffuse bluish stain, associated with gas emission.
The Lowell telescope, one of the largest to observe the comet, recorded the observationjeto a 16 graus do Sol. Zhang destaca que telescópios menores também podem captá-lo no crepúsculo matutino.
Composição química peculiar
Observações do Telescópio Espacial James Webb mostram uma coma dominada por dióxido de carbono. Essa proporção, incomum em cometas, sugere formação em condições distintas.
A presença de cianeto e níquel também foi detectada, similar a cometas do Sistema Solar. Essas características indicam que o 3I/ATLAS sofreu alterações por radiação cósmica.
A sublimação de gelo, intensificada no periélio, revela mais sobre sua estrutura. Pesquisadores aguardam novos dados para confirmar o tamanho do núcleo, estimado entre 0,32 e 5,6 km.
Global Observation Campaign
The International Asteroid Warning Network (IAWN) conducts training between November 2025 and January 2026. The focus is to improve astrometric measurements of the comet.
The exercise involves global telescopes, such as Gemini South and Hubble, to track the trajectory. Collected data will help predict the behavior of interstellar objects.
The comet poses no risk to Earth, being 270 million km away. The campaign aims only at scientific study, with no relation to planetary defense.
Interstellar origin under debate
3I/ATLAS, estimated to be 7 billion years old, may have come from the thick disk of the Milky Way. Its irradiated crust makes analysis of its original star system difficult.
Despite speculation about alien origin, most scientists dismiss the hypothesis. The object exhibits characteristics typical of comets, such as a coma and tail.
Unique study opportunity
The comet will be visible until December 2025, before leaving the Solar System. Space telescopes like James Webb plan new observations.
The scientific community sees 3I/ATLAS as a rare chance to study an interstellar object. Its chemical properties may reveal star formation processes.
New analyses, including ultraviolet spectroscopy using Hubble, are scheduled. Shes will clarify the gaseous composition and the ratio between sulfur and oxygen.
Visibility for amateur astronomers
3I/ATLAS, with magnitude 12, requires telescopes for observation. It appears on the eastern horizon, near the constellations Virgo and Leo.