Interstellar Comet 3I/ATLAS Changes Color: A Cosmic Chemistry Mystery
What Happened? The color-Changing Comet
When 3I/ATLAS was first spotted a few months ago, it seemed to emit a reddish color. But earlier this month, some astronomers noted it was glowing green. So why is our latest interstellar visitor appearing to switch colors like a traffic light? The answer isn’t certain, but it has something to do with cosmic chemistry.
First observed in early July 2025, 3I/ATLAS is a giant interstellar object that’s currently blasting through our Solar System. And, to dispel rumors, NASA confirms it’s not an advanced alien spacecraft.
What is 3I/ATLAS?
it’s an active comet consisting of a solid icy nucleus surrounded by a haze (known as a coma) of gas and ice. It’s notably exciting as it’s only the third time we have directly observed an object from another star pass through our Solar System, after ʻOumuamua and Comet 2I/Borisov.
The Shift in Color: From Red to Green
A bunch of observations in July suggested that 3I/ATLAS possessed a red coma,but that changed over the following weeks.
On september 7, amateur astrophotographers Michael Jäger and Gerald Rhemann snapped up some images of 3I/ATLAS during the “blood Moon” total lunar eclipse in Namibia. to their surprise, the object appeared green with a blue-ish tinge.
“Our images show a gas-rich coma of 2 arcminutes for the first time. It was clearly visible in both the blue and green filters,” Jäger told