Comet 3I/ATLAS With A Mysterious Anti-Tail Makes Its Closest Flyby: When, Where, And How To Watch It Live

Interstellar comet 3I/ATLAS is set to make its closest approach to Earth on December 19, giving skywatchers a rare chance to spot a visitor from another star system. What’s puzzling scientists most is its strange “anti-tail,” a feature pointing toward the Sun instead of away from it.

An unusual visitor from beyond our solar system has been making headlines and raising questions again. Interstellar comet 3I/ATLAS will pass closest to Earth on Friday, December 19, offering astronomers and stargazers a rare opportunity to observe an object that will never return. While there is no threat to Earth, the comet has sparked scientific excitement and curiosity due to a bizarre feature that defies normal comet behaviour.

What’s happening as Comet 3I/ATLAS nears Earth

Astronomers confirm that 3I/ATLAS will pass within about 268.9 million kilometres of Earth during its closest approach. Though that may sound close in cosmic terms, scientists stress it is safely distant and poses no danger whatsoever.

Discovered during summer sky surveys by the ATLAS telescope in Chile, the comet was initially flagged during scans designed to detect potentially hazardous asteroids. Follow-up observations quickly revealed something extraordinary: its trajectory proved it originated outside our solar system. This makes 3I/ATLAS only the third confirmed interstellar object ever detected.

As of December 14, the comet was roughly 270.5 million kilometres away. Due to the vast distances involved, images reaching Earth are delayed by around 15 minutes, the time light takes to travel that far. NASA has reiterated that the flyby is purely observational and completely safe.

What scientists are learning from 3I/ATLAS

Researchers continue tracking the comet as it gradually fades while speeding toward the edge of the solar system. Estimates place its size anywhere between 440 metres and 5.6 kilometres, a wide range reflecting the difficulty of measuring a fast-moving, dim object so far away.

The most intriguing mystery lies in its structure. Images captured since July reveal a bright feature extending toward the Sun, something astronomers call an “anti-tail.” Unlike typical comet tails, which stream away from sunlight due to solar radiation and wind, this anti-tail appears to defy expectations.

What’s more puzzling is its persistence. The feature remained visible through observations made as late as November, and scientists say changes in viewing angles cannot explain it away. Thousands of images confirm that the anti-tail is real and consistent.

Two peer-reviewed studies, including work co-authored by astrophysicist Eric Keto, suggest the effect may be caused by icy fragments scattering sunlight sunward. Another hypothesis proposes that radiation pressure may not be acting quickly enough on larger debris. A third study links the phenomenon to unusual acceleration effects, though research is ongoing.

When and how to watch the comet live

NASA advises skywatchers to look for the comet in the early hours before dawn on Friday. It will appear in the east to northeast sky and should be located below the bright star Regulus in the Leo constellation. While it won’t be visible to the naked eye, powerful binoculars or a backyard telescope should reveal it as a faint, glowing point of light.

NASA’s Chelsea Gohd has described this window as one of the best chances to see the comet, though visibility will depend heavily on local weather conditions.

For those unable to step outside, there’s still a way to watch. The Virtual Telescope Project will host a live stream starting at 11 pm Eastern Time on Thursday night, that is, 9:30 PM India Standard Time (IST), provided skies remain clear enough for observation.

Watch here:

What happens next for 3I/ATLAS

After its Earth flyby, the comet will head deeper into the solar system before making a close pass near Jupiter in March, coming within about 53 million kilometres of the gas giant. According to NASA scientist Paul Chodas, the comet will then continue on its hyperbolic path and is expected to leave the solar system entirely by the mid-2030s.

Scientists say this fleeting visit offers a rare scientific gift. Interstellar comets like 3I/ATLAS carry clues about environments far beyond our cosmic neighbourhood. While its home star system remains unknown, each observation helps researchers better understand how planetary systems form and how common such wandering objects may be across the universe.

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