Comet 3I/ATLAS, only the third confirmed interstellar visitor to our solar system, continues to fascinate scientists and space enthusiasts alike. Since its discovery in July, this cosmic wanderer has surprised observers with unexpected behaviors as it zips through our sunlit neighborhood.
Recent observations revealed that 3I/ATLAS underwent a dramatic brightening as it neared perihelion (its closest point to the Sun) on October 30th. This rapid brightening, captured by three spacecraft positioned in front of the Sun, surpassed what’s typically seen in comets at similar distances from our star. Analysis of this imagery, published on preprint server arXiv, suggested that 3I/ATLAS was notably bluer than the Sun, contrasting with earlier observations that indicated a reddish dust composition.
News outlets widely reported the comet “changed color” multiple times, often attributing it to mysterious causes. However, Qicheng Zhang, a postdoctoral fellow at Lowell Observatory and co-author of the study, clarifies this is a misinterpretation.
“We don’t have any evidence for the gas coma changing colors,” Zhang explained to Space.com. “Our result just showed that the gas coma is likely still around and contributing substantially to the overall brightness.”
Comets are often dubbed “dirty snowballs” due to their icy cores composed of frozen gases mixed with rock and dust particles. As a comet approaches the Sun, these frozen gases sublimate – transitioning directly from solid to gas – forming bright gaseous halos called “comas” that give comets their fuzzy appearance. The solar wind can further push these gases away, creating a long tail.
Zhang emphasizes that 3I/ATLAS has only appeared to change color once: when its coma brightened as it warmed up near the Sun earlier this year, before media reports focused on a supposed “color shift.” Amateur astronomer photographs from September already show the comet with a blue-green gas coma.
The comet’s journey has unfortunately spurred misinformation and outlandish speculation, including conspiracy theories about alien spacecraft or government cover-ups related to its nature.
Yet, 3I/ATLAS’ unexpected passage through our solar system offers valuable insights into environments beyond its confines. Despite the lack of imagery from NASA’s Mars Reconnaissance Orbiter due to the ongoing government shutdown, numerous ground-based and space telescopes, including Hubble and China’s Tianwen 1 mission, have captured images of this interstellar visitor.
The comet’s unique journey underscores the constant surprises lurking in the vastness of space and fuels our continuing quest to understand these elusive objects from beyond our cosmic neighborhood.
