NASA has reported that the interstellar comet 3I/ATLAS will reach its perihelion on October 29, 2025, at a distance of 1.36 astronomical units (AU) from the Sun, which is approximately 203 million kilometers. This event occurs after the comet was first detected on July 1, 2025, when it was positioned on the far side of the Sun from Earth, making initial observations challenging.
The GOES-19 satellite captured images of the comet on October 18, 2025, utilizing the CCOR-1 coronagraph. In these images, 3I/ATLAS appears as a small point of light, largely obscured by solar glare. The satellite, operated by the National Oceanic and Atmospheric Administration (NOAA), is in geostationary orbit, allowing for continuous monitoring of celestial phenomena. Citizen scientist Worachate Boonplod played a crucial role in identifying the comet in the satellite”s images.
As 3I/ATLAS approaches perihelion, it is expected to exhibit increased activity due to solar radiation causing sublimation from its icy nucleus. The hyperbolic trajectory of the comet suggests it is not bound to the solar system and originates from another stellar system. Notably, its orbital inclination is significantly different from that of the planets, and it crossed the orbit of Mars on October 3, 2025, at a safe distance.
The CCOR-1 coronagraph blocks the Sun”s central disk, simulating a total eclipse, which facilitates the study of the solar corona. During the October 18 observation, the comet was located at the edge of the field of view, maintaining a consistent position across several frames, thus confirming its identity as 3I/ATLAS.
On October 26, 2025, the comet will be positioned directly behind the Sun from Earth”s perspective, making ground-based observations impossible due to solar glare. However, simulations from the Jet Propulsion Laboratory (JPL) indicate that the Earth, Sun, and comet will form a near-linear alignment.
Following perihelion, visibility of 3I/ATLAS from terrestrial locations is expected to improve starting November 8, as the comet begins to move angularly away from the Sun. By November 11, it will be observable in the eastern morning sky, located near the star Spica in the constellation Virgo. Observers will need telescopes with a minimum aperture of 20 centimeters to successfully capture images of the comet, which is predicted to reach apparent magnitudes between 13 and 14.
In addition to ground observations, the European Space Agency (ESA) plans to utilize its JUICE probe to gather data on the comet on November 2, employing optical instruments and spectrometers. This mission aims to maximize data collection during the post-perihelion phase when the comet”s activity is expected to be at its peak.
As 3I/ATLAS continues its journey, it will cross the orbital plane of Jupiter on March 20, 2026, allowing for joint observations with the gas giant, which will serve as a bright reference point. The comet”s trajectory and characteristics will be analyzed in detail to better understand its composition, including the presence of complex organic compounds like hydrogen cyanide.
The arrival of 3I/ATLAS offers a remarkable opportunity for astronomers to study interstellar visitors, contributing valuable insights into the formation of planetary systems. This comet represents the third known interstellar object observed, joining the ranks of 1I/”Oumuamua and 2I/Borisov. The ongoing observations and data collection are expected to shape future research and enhance our understanding of objects originating beyond our solar system.
