Something unusual is occurring in our solar system. The interstellar comet 3I/ATLAS, which has gained significant attention among astronomers, has reportedly shifted its color once more, now exhibiting a faint blue glow. This transformation marks the third color change since its discovery in July 2025, and researchers are eager to uncover the reasons behind the comet”s unpredictable behavior.
This latest change followed a sudden increase in brightness while 3I/ATLAS was obscured by the Sun, just days after it reached perihelion, its closest approach to the Sun, on October 29. The comet”s brightness surged unexpectedly, far exceeding what could be attributed solely to solar heating. Upon reappearing, telescopes began to detect a delicate shimmer of blue light, shifting away from its previously observed red and green phases.
Experts theorize that the comet”s color variations are the result of volatile gases escaping as sunlight warms its icy core. Each color provides insight into the comet”s composition: red indicates the presence of dust and organic materials, green suggests carbon-based gases, and the recent blue hue may result from carbon monoxide or ammonia being released from the comet”s surface. If confirmed, this color shift could offer valuable information about the evolution of ancient interstellar comets that have drifted through space for billions of years.
As of November, 3I/ATLAS is becoming visible again to observers in the Northern Hemisphere, though it will not be discernible to the naked eye. Telescopes are set to capture its soft glow in the early morning sky before sunrise. The comet is expected to make its closest approach to Earth on December 19, 2025, safely passing at a distance of about 270 million kilometers.
Discovered hurtling into our solar system at speeds exceeding 210,000 kilometers per hour, 3I/ATLAS is only the third interstellar object ever recognized. Believed to be over seven billion years old, this comet is thought to have been ejected from its original star system located on the outskirts of the Milky Way before embarking on its solitary journey through interstellar space.
