(Caption: Hubble image of 3I/ATLAS. White dashes on a black background. New observations reveal that 3I/ATLAS may be turning blue. This image, taken by the Hubble Space Telescope in August, was captured using a colored filter and does not represent the comet's current appearance. (Image credit: NASA/ESA)
'Interstellar visitor' 3I/ATLAS may have just changed color — for the third timeRecent observations of the interstellar object 3I/ATLAS show that it has developed a faint blueish hue, hinting at a potential color change. This is the third time experts have seen the comet's coloring shift since it was discovered.
Interstellar comet 3I/ATLAS may be developing a blueish hue after undergoing a rapid and unexpected brightening event while hidden behind the sun, new observations reveal. This is the third time that experts have noted a potential change to the comet's color — but, so far, none of them have stuck.
3I/ATLAS, the third-known interstellar object to visit our solar system, was spotted shooting toward the sun at more than 130,000 mph (210,000 km/h) in early July.
The comet is potentially the oldest of its kind ever seen and was likely ejected from its home star system, somewhere in the Milky Way's frontier, more than 7 billion years ago. Since then, it has sailed through interstellar space, before making its current rendezvous with our solar system.
Following a close approach to Mars at the start of October, the interstellar comet has spent the last few weeks on the opposite side of the sun to Earth, making it largely unobservable from our planet (although a handful of orbiting spacecraft could still see it). But it is now starting to become visible to Earth-based telescopes once again.
A gray scale image showing various white dots of stars and comets with a large smudge in the middle which is the interstellar comet 3I/ATLAS
I watched scientists view the interstellar comet 3I/ATLAS in real time. Here's what they saw. Hubble captured this image of the interstellar comet 3I/ATLAS on July 21, 2025, when the comet was 277 million miles from Earth. Hubble shows that the comet has a teardrop-shaped cocoon of dust coming off its solid, icy nucleus.
The comet reached its closest point to the sun, known as perihelion, on Oct. 29, when it was mostly hidden from us, reaching a minimum distance of 130 million miles (210 million kilometers) from our home star — around 1.4 times farther from the sun than Earth. The day before, a pair of researchers analyzing data from spacecraft that could still see 3I/ATLAS revealed that the comet had brightened by several orders of magnitude after disappearing from view, which can't be fully explained by its proximity to the sun.
In the same paper, the researchers also wrote that the comet appears to be "distinctly bluer than the sun," which came as a surprise given that this color had not been seen in the comet until now. This color change is likely the result of a specific gas, such as carbon monoxide or ammonia, leaking from the comet, they argued. (This study has not yet been peer-reviewed, and no other observations have thus far confirmed the blue coloration.)
(Image: This photo, taken by astrophotographers Michael Jäger and Gerald Rhemann, showed 3I/ATLAS with a green glow on Sept. 7. (Image credit: Michael Jäger/Gerald Rhemann)
The researchers noted that the blue coloration is in sharp contrast to the initial red hue given off by the comet during early observations in July, which was likely the result of an abundance of dust coming off its surface. Then, in September, the comet briefly appeared to be turning green, likely due to the presence of dicarbon or cyanide within its coma.
But these changes of coloration were only temporary, and it's currently unclear why that is. Only time and continued observations will tell if the comet's new coloring will stick.
No comments:
Post a Comment