The mysterious interstellar object 3I/ATLAS, which drew global attention for allegedly changing colors during its close encounter with the Sun, did not actually undergo any real color transformation, NASA-linked scientists have confirmed.
According to a report by Space.com, several media outlets recently claimed that the comet had dramatically shifted from red to blue-green hues, sparking speculation about unusual cosmic activity. However, experts have clarified that the observed blue-green tint is natural and not evidence of any mysterious phenomenon.
3I/ATLAS: A Rare Visitor From Beyond the Solar System
Discovered in July 2025, 3I/ATLAS is only the third confirmed interstellar object to enter our solar system — following ‘Oumuamua (2017) and 2I/Borisov (2019). The object made its closest approach to the Sun on October 30, when three solar observatories captured images showing a sudden increase in brightness.
These images revealed that 3I/ATLAS appeared “distinctly bluer than the Sun,” according to a preprint study published on arXiv. The finding led to viral headlines claiming the comet had “changed color.” But Qicheng Zhang, a postdoctoral fellow at the Lowell Observatory in Arizona and co-author of the study, has since clarified that this interpretation was incorrect.
No Actual Color Change, Says Scientist
Speaking to Space.com, Zhang explained that the comet’s color remained consistent.
“We don’t have any evidence for the gas coma changing colors,” he said. “Our result just showed that the gas coma is still around and contributing to the overall brightness.”
According to Zhang, the blue-green glow is not a new feature but a natural result of the comet’s composition and interaction with sunlight. The color arises from the gas coma — a luminous cloud of dust and vapor surrounding the nucleus — formed when solar heat causes frozen materials on the comet to sublimate.
Why Comets Glow Blue-Green
Comets are often referred to as “dirty snowballs” because of their icy nuclei mixed with dust and rock. As they near the Sun, these ices vaporize, forming a glowing coma. When sunlight interacts with molecules such as diatomic carbon (C₂) and cyanogen (CN), it produces a distinct bluish-green light — a feature seen in many active comets, including 3I/ATLAS.
Zhang further noted that the comet’s apparent “color change” likely occurred once, earlier this year, when its gas coma first became visible. Since then, it has remained consistently blue-green — only brighter as solar activity increased.
A Rare Glimpse Into the Cosmos
Beyond its color, 3I/ATLAS holds immense scientific value. As an interstellar object, it originated from outside our solar system, making it a rare visitor carrying material from another star’s planetary system.
Studying such objects helps astronomers understand how other solar systems form and evolve. The data gathered from 3I/ATLAS’s trajectory and composition could also reveal how interstellar objects travel through space and interact with stellar environments like ours.
FAQs
What is 3I/ATLAS?
3I/ATLAS is the third known interstellar object to enter our solar system. Discovered in July 2025, it is believed to have originated from a distant star system.
Did 3I/ATLAS really change color?
No. NASA-affiliated scientist Qicheng Zhang confirmed that the comet’s blue-green appearance is natural, caused by gases like diatomic carbon and cyanogen glowing under sunlight — not an actual color change.