Bengaluru, India – As interstellar comet 3I/ATLAS continues its journey out of the inner solar system, scientists at the Indian Space Research Organisation's (ISRO) Physical Research Laboratory (PRL) are diligently tracking its trajectory and studying its composition. Discovered on July 1, 2025, by the Asteroid Terrestrial-impact Last Alert System (ATLAS) in Chile, 3I/ATLAS is only the third confirmed interstellar object to be observed passing through our solar system, following 1I/ʻOumuamua and 2I/Borisov.
Comet 3I/ATLAS, also designated as C/2025 N1, is currently moving away from the Sun after reaching its closest point on October 29, 2025. At perihelion, it came within 1.35 AU of the Sun, placing it just inside the orbit of Mars. While its trajectory brought it relatively close to Venus, Mars and Jupiter, it poses no threat to Earth. On December 19, 2025, it will pass 1.80 AU (269 million km) from Earth.
ISRO, in collaboration with NASA, utilizes a combination of ground-based observatories and space-based assets to monitor comets like 3I/ATLAS. NASA's ATLAS system employs wide-field telescopes in Chile and Hawaii to scan the skies nightly, detecting moving objects and helping scientists to accurately track their orbits. ISRO contributes to these efforts through ground observatories and potentially through the joint NASA-ISRO Synthetic Aperture Radar (NISAR) satellite, though its specific role in tracking 3I/ATLAS isn't detailed.
Scientists are particularly interested in 3I/ATLAS due to its unique characteristics and interstellar origin. Interstellar comets provide a rare opportunity to study the composition of planetary systems beyond our own. Observations of 3I/ATLAS have revealed that it brightened at an unexpectedly faster rate than typical comets as it approached the Sun, possibly due to its distinct chemical composition. As the comet neared the Sun, its icy shell vaporized, creating a coma several thousand kilometers wide. However, the comet's tail appeared shorter and weaker than expected, potentially due to the viewing angle from Earth or a hardened crust on its surface limiting gas and dust ejection.
The comet's color has also been a subject of interest. Some reports suggested that 3I/ATLAS exhibited multiple color changes, sparking speculation. However, further analysis indicated that the comet likely changed hue only once as it brightened, a natural phenomenon possibly caused by carbon molecules fluorescing under ultraviolet light.
Throughout its journey through the solar system, 3I/ATLAS has been extensively observed by both professional and amateur astronomers. Over 600 observations have been recorded, contributing to a wealth of data and over 70 research papers. NASA also held a live event on November 19, 2025, to share imagery of the interstellar comet 3I/ATLAS collected by various NASA missions.
As 3I/ATLAS departs the inner solar system in January 2026, it will continue to be a subject of scientific investigation. The data collected during its passage will undoubtedly provide valuable insights into the nature and origins of interstellar objects, furthering our understanding of the cosmos.
