Interstellar Comet 3I/ATLAS: NASA and Hubble Reveal a Rare Visitor’s Solar System Journey

What Makes 3I/ATLAS an Interstellar Rarity?

Every so often, a cosmic wanderer drops into our solar system from the depths of interstellar space. In July 2025, astronomers confirmed the arrival of such a visitor: 3I/ATLAS, only the third interstellar comet ever observed by humankind. Its discovery, made by the ATLAS (Asteroid Terrestrial-impact Last Alert System) survey telescope in Chile, immediately set off a flurry of activity among scientists eager to study a body forged far beyond our solar neighborhood.

Unlike the majority of comets that trace elongated paths around our Sun, 3I/ATLAS boasts a hyperbolic trajectory, indicating it originated outside the gravitational embrace of our solar system. Upon discovery, it was located at a heliocentric distance of 4.51 astronomical units (AU) and was speeding through space at an extraordinary velocity of 58 km (36 miles) per second. Its path brought it in from the direction of Sagittarius, setting the stage for a journey unlike any local comet’s.

Close Encounters: From Mars to the Sun

3I/ATLAS’s itinerary through the solar system has been as dramatic as its origins. On October 3, the comet made a close approach to Mars, skimming past the Red Planet at a distance of just 0.194 AU. Later that month, on October 30, it reached perihelion—its closest point to the Sun—before continuing its outbound trek. By March 2026, it is expected to pass near Jupiter, offering astronomers another opportunity to study its composition and behavior.

NASA’s PUNCH mission, designed to observe the solar wind and its interactions with comets, managed to capture 3I/ATLAS during its time-lapse imaging of Comet SWAN. In a remarkable 40-day sequence, the spacecraft not only tracked SWAN’s dramatic evolution but also briefly caught 3I/ATLAS zipping beneath SWAN near the end of the sequence. These observations highlight the comet’s rapid movement and fleeting visibility, underscoring how rare such interstellar visitors truly are.

Hubble’s Teardrop Halo: A Cosmic Signature

While ground-based telescopes and spacecraft provide crucial data, the Hubble Space Telescope has delivered some of the most striking images of 3I/ATLAS. Using its Wide Field Camera 3, Hubble captured a new portrait of the comet on November 30, 2025. The image reveals a teardrop-shaped glowing halo—known as the coma—extending towards the Sun, with a sunward anti-tail stretching as far as 60,000 km (37,282 miles).

According to Harvard University’s Professor Avi Loeb, this unusual shape is more than just a visual spectacle. The teardrop extension may represent a swarm of macroscopic non-volatile objects that separated from the comet due to non-gravitational acceleration away from the Sun. Loeb’s prediction that these objects would be closer to the Sun than the main body by November 30 was confirmed by the Hubble image, providing rare insight into the physical processes shaping interstellar comets.

“Hubble tracked the comet as it moved across the sky,” NASA’s statement noted. “As a result, background stars appear as streaks of light.” This technique, called tracking, enables scientists to study the comet’s coma and tail in unprecedented detail, helping to distinguish between material ejected from the nucleus and particles swept away by the solar wind.

Interstellar Insights: What 3I/ATLAS Reveals

Why does the scientific community care so deeply about interstellar comets? These objects are time capsules, carrying material from distant star systems and offering a window into cosmic processes that shaped worlds beyond our own. Each new observation of 3I/ATLAS is a chance to probe the chemical and physical properties of matter that was never part of our Sun’s family.

The comet’s teardrop-shaped coma, its rapid velocity, and its non-gravitational acceleration all hint at a complex interplay of forces. By studying these features, astronomers hope to learn more about the composition of interstellar material, the mechanisms that eject comets from their home systems, and the impact of solar radiation on icy bodies from afar. As 3I/ATLAS continues its outbound journey, it remains under the watchful gaze of telescopes on Earth and in orbit. Observations are expected to continue for several months as the comet recedes into deep space, carrying the secrets of its origins with it.

Shared Skies: A Moment of Cosmic Intersection

In a twist worthy of cosmic coincidence, 3I/ATLAS’s passage through the inner solar system coincided with the journey of Comet SWAN. NASA’s PUNCH mission offered a rare visual of two comets—one local, one interstellar—sharing the same swath of sky. While SWAN dazzled observers with its bluish-green coma and unusual triangular shape (likely due to a fragmenting nucleus), 3I/ATLAS appeared as a swift, distant traveler. Together, their images serve as a vivid reminder of the solar system’s openness to visitors from afar and the diversity of bodies orbiting our Sun.

For amateur astronomers and skywatchers, the close approach of both comets in late 2025 was a fleeting spectacle, with SWAN nearly visible to the naked eye and 3I/ATLAS detectable with advanced equipment. Such events are not just scientific milestones; they’re moments of wonder, inviting all who gaze skyward to ponder the vastness of space and the mystery of origins.

As the third confirmed interstellar comet to grace our skies, 3I/ATLAS stands as a scientific landmark and a messenger from beyond. Its rare journey, tracked by NASA and immortalized by Hubble, is reshaping our understanding of cosmic wanderers and the forces that guide them. The evidence of non-gravitational acceleration and macroscopic debris opens new questions about the physics of interstellar comets, their formation, and their fate. In the coming months, continued observations promise deeper insight, reminding us that the universe still holds surprises for those who look up.