The buzz surrounding Comet 3I/ATLAS has yet to die down as a mysterious object from beyond our solar system races toward its closest approach to Earth. Flying past the Sun at a breakneck speed of 153,000 mph, 3I/ATLAS is now scheduled to fly past Earth on Friday, December 19, 2025.
While astronomers eagerly await this anticipated flyby, they will have time to scrutinize the latest 3I/ATLAS images from NASA's Hubble Telescope and the European Space Agency's Jupiter Icy Moon Explorer (Juice). These observations have given astronomers new insight into the features that make 3I/ATLAS so unlike any other comet. More detailed information will appear next year, when this interstellar guest leaves the solar system.
Read more: New images of comet 3I/ATLAS show how magical the Universe could be
The bright blue glow of 3I/Atlas
In a recent image taken by NASA's Hubble Space Telescope, Comet 3I/ATLAS striking with a bright blue glow surrounding its core, visible as a tiny white speck. This latest observation, recorded on November 30 by Hubble's Wide Field Camera 3, shows the comet to be 178 million miles from Earth. A few faint streaks of light in the background are distant stars, as they have looked like this ever since Hubble took this image as 3I/ATLAS moved across the sky.
Back in late July, shortly after 3I/ATLAS was first discovered, NASA shared a similar, albeit lower resolution, image of the comet, which was also taken by Hubble. Like the last image, this one shows the blue glow of 3I/ATLAS.
What makes 3I/ATLAS so bright and blue? Comets typically become brighter as they approach the Sun when radiation causes solid ice to turn into gas through a process called sublimation. Gas and dust then form around the comet, forming its coma, which appears as a glowing aura, and its tail. The brightness is caused by sunlight reflecting off dust in the coma and tail.
However, 3I/ATLAS is unusually bright for a comet. This may be due to his lack of dust mantlea feature that most comets have that can soften the harsh brightness. And while other comets typically tend to turn redder as their dust reflects scattered sunlight, 3I/ATLAS retained a blue-green hue that may be caused by a combination of gases—possibly cyanogen and ammonia—ejected from the comet's body.
Two tails appear
Another 3I/ATLAS image taken by ESA's Juice spacecraft on November 2 does not show the comet's blue stream, but does show hints of two tails. Five science instruments on Juice were used to collect information about the comet's behavior and composition, and the spacecraft's onboard Navigation Camera (NavCam) captured the image.
Although the data collected by the five instruments won't be available to researchers until mid-February 2026, the NavCam image provides insight into the comet's activity.
The image shows a bright spot where the 3I/ATLAS coma is present, as well as two lines branching from the coma that appear to be tails. One of them is the comet's plasma tail, a stream of electrically charged gas stretching toward the top of the image. The other is the comet's suspected dust tail, a fainter stream of tiny particulate matter directed toward the lower left corner of the image.
Observing an interstellar visitor
More images and observations of Comet 3I/ATLAS are expected in the coming months as other telescopes join the effort.
Astronomers will monitor the comet as it approaches Earth; its closest approach to our planet—about 168 million miles—is not close enough to cause any concern. When the comet passed Mars on October 3, 2025, it was only 18 million miles away.
Early December will be the best time to view 3I/ATLAS from Earth with good binoculars or a telescope. According to theskylive.com, it will pass through the constellations Virgo and Leo and become much fainter by the end of the year.
Read more: When was Halley's Comet last seen and will it ever return?
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