On Sept. 7 2025, the skies darkened as Earth’s shadow consumed the moon. Skywatchers in lots of elements of the world noticed the moon flip blood pink on account of a complete lunar eclipse.
For novice astronomers Michael Jäger and Gerald Rhemann in Namibia, the eclipse was not solely a sight to behold, nevertheless it additionally gave them an unprecedented alternative: the possibility to seize the interstellar comet 3I/ATLAS underneath a number of the darkest skies on Earth.
Using the eclipse’s pure dimming of the moon, the duo was able to take some deep images of the comet, revealing one thing shocking: the comet glowed inexperienced.
What is it?
3I/ATLAS is barely the third confirmed interstellar comet observed passing through our solar system and where it originated from is still a mystery. The comet is classified as interstellar because its trajectory is hyperbolic, meaning it’s not gravitationally bound to the sun and most likely originated in another star system (at least that’s the most likely theory).
It follows in the footsteps of two other famous interstellar objects: ‘Oumuamua, a cigar-shaped body that still sparks debates about its nature, and comet 2I/Borisov, the first confirmed interstellar comet, which displayed more of a typical dusty coma and tail.
Now, 3I/ATLAS provides astronomers with another rare chance to study the chemistry of material formed around a completely different star.
Where is it?
This photograph was taken in the Kalahari Desert in Namibia, Africa.
Why is it amazing?
This is the first image showing a green hue to 3I/ATLAS, hinting at its unique chemistry. With the darkness provided by the lunar eclipse, the first explanation for this green color is that the comet may have diatomic carbon (C2). This molecule, made of two carbon atoms bonded together, is known to fluoresce a green glow when energized by sunlight.
However, in August, astronomers at Kitt Peak Observatory in Arizona discovered that 3I/ATLAS is definitely poor in carbon-chain molecules, together with diatomic carbon. This begs the query nevertheless, if diatomic carbon was absent solely a month earlier, how is the comet all of a sudden inexperienced now?
One chance is that heating by the solar triggered recent layers of ice to soften and launch hidden diatomic carbon molecules that have been beforehand trapped beneath the floor. Another chance is that the inexperienced glow is coming from different molecules which additionally glow underneath daylight. Because 3I/ATLAS is interstellar, it could comprise chemistry not generally seen in our photo voltaic system comets, resulting in a false “classic” inexperienced glow from an unfamiliar supply.
Whatever the trigger, 3I/ATLAS stays a thriller in lots of facets as astronomers proceed to review it because it strikes by our photo voltaic system.
Want to be taught extra?
You can learn extra about imaging 3I/ATLAS and its journey toward the sun.