NASA reports that the interstellar comet 3I/ATLAS is set to reach its perihelion on October 29, 2025. This event marks the closest approach of the comet to the Sun, occurring at a distance of 1.36 astronomical units, which is approximately 203 million kilometers.
The GOES-19 satellite captured images of comet 3I/ATLAS on October 18, 2025, utilizing the CCOR-1 coronagraph. In these images, the comet appears as a faint point obscured by solar glare. The equipment is operated by the National Oceanic and Atmospheric Administration (NOAA) and is positioned in geostationary orbit. Citizen scientist Worachate Boonplod played a crucial role in identifying the comet within the satellite”s imagery.
Discovered on July 1, 2025, 3I/ATLAS was initially located on the far side of the Sun from Earth. Ground-based telescopes collected the first observations, revealing that the comet follows a hyperbolic orbit, indicating it is moving at a speed greater than the solar escape velocity. This trajectory suggests that the comet is not bound to the solar system and originates from another stellar system.
The orbital inclination of 3I/ATLAS is notably high, diverging significantly from the plane of the solar system”s planets. The comet crossed Mars” orbit safely on October 3, 2025, and subsequent observations confirmed its predicted trajectory. As it approaches the Sun, the comet”s activity increases due to the sublimation of gases from its icy nucleus, resulting in a growing coma and tail.
The CCOR-1 coronagraph effectively blocks the Sun”s central disk, simulating a total eclipse and allowing astronomers to study the outer solar corona. In the images taken on October 18, the comet was positioned at the edge of the field of view, maintaining a consistent position across multiple frames. The GOES-19 satellite”s geostationary orbit enables continuous monitoring of the comet”s movement.
On October 26, 2025, 3I/ATLAS will align directly behind the Sun from Earth”s perspective, limiting visibility due to solar glare. Simulations from the Jet Propulsion Laboratory (JPL) illustrate this configuration, showing Earth, the Sun, and the comet forming a near-straight line with minimal angular separation.
Perihelion is anticipated to occur on October 29 at 1.36 AU, placing the comet within the average orbit of Mars. As solar radiation intensifies, models predict a surge in the production of gas and dust, with the coma expanding significantly and the tail potentially extending millions of kilometers.
The composition of 3I/ATLAS includes typical elements found in interstellar comets, with spectroscopy revealing the presence of carbon monoxide and cyanide. Visibility from Earth is expected to improve starting November 8, as the comet moves away from the Sun. By November 11, it will become observable in the eastern morning sky, located in the constellation Virgo near the star Spica. Telescopes with a minimum aperture of 20 centimeters will be necessary for detection, with predicted magnitudes ranging from 13 to 14.
Data from Brazilian astronomers who took pre-conjunction images, including contributions from Cristóvão Jacques and Diego, indicate that the apparent magnitude of the comet will peak near 13 at perihelion before declining as it moves further away from the Sun. Initial observations noted a magnitude of 18 at discovery, with recent data showing values around 14.
Projections from the European Space Agency (ESA) validate these models, highlighting how geometric factors influence visibility. The comet”s phase will continue to change as it travels through the solar system. The JUICE probe is scheduled to observe the comet on November 2, utilizing optical instruments and spectrometers to gather data. A second observation session will take place on November 25, capitalizing on favorable spacecraft positioning to capture high-resolution images of the tail structure.
3I/ATLAS stands out from the native solar comets, offering a unique opportunity for comparative studies. The comet will cross the Jovian orbital plane on March 20, 2026, allowing for joint observations with Jupiter serving as a bright reference point. The configuration will enable precise astrometry, refining the comet”s orbital parameters.
With an eccentricity exceeding 1, 3I/ATLAS travels at a hyperbolic velocity of 30 kilometers per second upon entry. Comparisons with known interstellar objects, such as 1I/”Oumuamua and 2I/Borisov, reveal shared kinematic characteristics, while its spectra indicate the presence of complex organic compounds like hydrogen cyanide.
The comet represents the third interstellar sample, providing valuable data to enhance our understanding of planet formation. Multi-wavelength observations spanning from radio to ultraviolet are coordinated through global networks, with alerts disseminated via the Central Bureau for Astronomical Telegrams due to the scientific interest surrounding this rare event. Observatories in the southern hemisphere, particularly in Chile and South Africa, will play a significant role in monitoring the comet.
As 3I/ATLAS accelerates away from the solar system post-perihelion, its trajectory will point toward a specific constellation. Continuous monitoring with space telescopes will occur for decades, and infrared sensors will be employed to detect residual thermal signatures. Archived data will remain accessible for future generations, with databases like the Planetary Data System hosting comprehensive records. The comet”s visit underscores the growing interest in interstellar visitors, marking a new era in astronomical exploration.
