Kathrine Frich
For astronomers, color can reveal the hidden chemistry of space.
The shifting glow of distant objects often hints at the gases, dust, and radiation shaping their paths through the cosmos.
Each variation tells a story about how these travelers form, move, and fade.
A changing hue
Researchers observing the interstellar comet known as 3I/ATLAS say it may have developed a faint bluish tint, the third apparent color change since its discovery earlier this year, according to Live Science.
The object briefly disappeared from Earth’s view while passing behind the Sun, then reappeared brighter and possibly blue.
The comet, first detected in July, is only the third known visitor from beyond our solar system.
It is estimated to be more than seven billion years old and to have travelled across interstellar space before entering our planetary neighborhood.
Tracing its journey
After a close pass near Mars in early October, 3I/ATLAS moved behind the Sun, leaving only orbiting spacecraft able to observe it.
New data now show that the object brightened unexpectedly during that period.
In a recent preprint study, two scientists suggested that the color shift may be caused by gases such as carbon monoxide or ammonia escaping from its icy surface.
Earlier this year, the comet appeared red, then green, both shades linked to different molecules in its coma, the luminous cloud that surrounds its core.
Uncertain explanation
So far, no other team has confirmed the bluish color, and astronomers caution that it could fade again.
The cause of its changing hues remains unclear, though experts note that sunlight and heat can alter the gases released as a comet nears its closest point to the Sun.
Images from August taken by the Hubble Space Telescope and from ground-based observatories show 3I/ATLAS surrounded by a wide dust halo.
Each observation adds clues about its makeup and history, but also raises new questions about how such ancient material behaves.
What happens next
The comet will become easier to observe from the Northern Hemisphere in the coming weeks, though it will remain invisible to the naked eye.
Astronomers recommend telescopes or powerful binoculars for viewing as it approaches its closest pass to Earth on December 19.
By then, researchers hope to determine whether the blue tint signals a lasting transformation or just another brief episode in the life of one of the galaxy’s rare interstellar wanderers.
Sources: Live Science, NASA, ESA, International Gemini Observatory
This article is made and published by Kathrine Frich, who may have used AI in the preparation
