Farewell tour: 3I/ATLAS to grace Earth’s skies before leaving solar system. How to watch

An interstellar comet that journeyed into our solar system from deep space has just made its closest approach to the Sun — and astronomers say it’s now heading back out, offering a final window for observation. Officially named 3I/ATLAS, the comet came within 126 million miles (203 million km) of the Sun, according to EarthSky. 

Currently hidden behind the Sun, 3I/ATLAS will reappear in Earth’s skies by mid-November, visible in the predawn hours. Stargazers should mark November 11 on their calendars for the first opportunity to spot it, with the best views expected 90 minutes before sunrise, looking eastward under dark, clear skies. 

How to See It 

This isn’t a naked-eye event — astronomers recommend a telescope with at least an 8 to 10-inch aperture to catch the faint visitor. The viewing window will stretch through December 2025, providing both skywatchers and scientists ample time to observe this cosmic traveller. 

The comet will make its closest approach to Earth on December 19, passing safely at 168 million miles (270 million km) — a comfortable distance, the European Space Agency (ESA) confirmed. 

Only the third of its kind 

3I/ATLAS is just the third known interstellar object to pass through our solar system, following the mysterious ‘Oumuamua (2017) and comet Borisov (2019). These objects offer invaluable clues about the building blocks of planetary systems beyond our own. 

Often dubbed “dirty snowballs,” comets like 3I/ATLAS are composed of ice, dust, and rock — ancient remnants from the dawn of solar system formation. As they heat up near the Sun, their outgassing helps astronomers decipher their chemical fingerprints. 

Recent data from the James Webb Space Telescope (JWST) and NASA’s upcoming SPHEREx mission detected carbon dioxide, carbon monoxide, carbonyl sulfide, and water ice coming off the comet’s surface — key markers of its interstellar origins. 

“When it gets closest to the Sun, you get the most holistic view of the nucleus possible,” said Darryl Seligman, astrophysicist at Michigan State University. “It shows you the original material it formed from — essentially, a snapshot of another solar system’s beginnings.” 

Alien speculation debate 

As 3I/ATLAS draws scientific attention, it has also ignited a familiar wave of online speculation. Some conspiracy theories, echoing earlier debates around ‘Oumuamua, suggest the comet might be an alien spacecraft. 

Physicist Brian Cox, however, has firmly dismissed such claims, calling them “drivel.” In a post on X (formerly Twitter), Cox clarified, “Just to be clear – given recent drivel online – Comet 3I/ATLAS is a comet, made of carbon dioxide and water ices and bits of other stuff. It is entirely natural in origin, its orbit is as expected, and it will whizz around the Sun and then disappear off into the galaxy again.” 

His remarks counter ongoing speculation from Harvard astrophysicist Avi Loeb, who has proposed that some interstellar visitors might be artificial.