‘Interstellar visitor’ 3I/ATLAS may have changed colour — again

The mysterious interstellar object 3I/ATLAS appears to have shifted to a faint blue hue — its third suspected colour change since astronomers first spotted it.

Does that confirm it's more than a comet from another star?

New observations suggest the comet brightened dramatically while hidden behind the sun, triggering this latest transformation.

3I/ATLAS — only the third confirmed interstellar visitor to pass through our solar system — was observed racing toward the sun in July at over 130,000 mph (210,000 km/h).

Researchers believe the object may be more than 7 billion years old, likely flung from a distant star system on the outer edge of the Milky Way long before our solar system even formed.

After a brief encounter near Mars in early October, the comet disappeared from Earth’s view as it moved behind the sun.

A few spacecraft continued tracking it, but ground-based observations were largely impossible.

Now that it is re-emerging, astronomers are surprised to see its glow subtly shift toward blue — a change that could point to volatile ices being exposed or gas jets releasing fresh material from its surface.

Harvard astrophysicist Avi Loeb wrote: "If 3I/ATLAS is a comet of natural origin, it could disintegrate into fragments as it comes closer to the Sun. We should keep our eyes on this fuzzy ball of light and check whether it breaks up into independent smaller dots of light."

"Comets disintegrate primarily as a result of heating by the sun, but sometimes also by gravitational tides and rotational stress from outgassing. The catastrophic breakup of a comet into multiple fragments is difficult to forecast without knowing its detailed composition and material strength."

Despite multiple suspected colour changes, none have been confirmed as permanent.

Scientists are eager to see whether the object's new tint persists as it continues its high-speed tour through the inner solar system.

As 3I/ATLAS becomes easier to observe in the coming weeks, telescopes around the world will be watching: each glimpse could provide rare clues into the chemistry and evolution of objects formed far beyond our cosmic neighbourhood.