Interstellar Visitor 3I/ATLAS Reveals Wobbling Jets in Sun-facing Anti-Tail as It Heads Toward the Outer Solar System
Breaking space news: The interstellar comet 3I/ATLAS continues to yield new clues as it moves away from the Sun, with researchers documenting wobbling jet activity inside its sun-facing anti-tail.
New measurements show jet structures stretching up to 620,000 miles (1 million kilometers) that rotated with a cadence of roughly seven hours and 45 minutes as the object neared perihelion.
Comets typically display tails trailing away from the Sun, but a rare anti-tail, an inverted tail pointing toward the Sun, appeared in 3I/ATLAS’s coma during its approach. The finding comes from 37 nights of observations conducted from July 2 to September 5, 2025, using the Two-meter Twin Telescope at Teide Observatory in Tenerife, Canary Islands.
The study notes a conversion from a sunward dust fan to a pronounced antisolar tail as solar radiation heated the coma, culminating in a close solar approach on October 30, 2025, at about 130 million miles (210 million kilometers) from the Sun.
Additionally, the anti-tail’s jets demonstrated a wobble, or precession, implying the nucleus rotates about once every 15 hours and 30 minutes-faster than previously estimated.
3I/ATLAS is only the third known interstellar object to pass through our solar system, following ‘Oumuamua in 2017 and 2I/Borisov in 2019. While interstellar visitors are rare, scientists have noted sun-facing anti-tails before; what sets 3I/ATLAS apart is the first observation of outgassing from an interstellar comet, as described in a paper posted to arXiv.
Experts describe this as a rare window into the physical nature of a pristine body formed around another star. The arXiv posting of the study provides more technical detail for researchers and space scientists. Readers can consult Space.com coverage, and NASA and ESA materials for broader context.
The team behind the discovery observed 3I/ATLAS for 37 nights between July 2 and september 5, 2025, with the Two-meter Twin Telescope (TTT), a robotic facility at Teide Observatory in Tenerife, Spain. The data track the coma’s evolution from a sun-facing dust fan to a pronounced antisolar tail as the comet approached the Sun.
According to the researchers, the anti-tail appeared on seven nights between August 3 and August 29, with jet activity indicating the icy core spins roughly once every 15.5 hours. This rotational period is shorter than earlier estimates for 3I/ATLAS.
Since then, 3I/ATLAS has continued its journey outward, passing Earth’s vicinity on December 19 at about 168 million miles (270 million kilometers) away. It is expected to continue sailing toward the outer reaches of the solar system and eventually depart,much like Oumuamua and Borisov did.
| Key Fact | Details |
|---|---|
| Object | Interstellar comet 3I/ATLAS |
| observation window | July 2 – Sept. 5, 2025 (37 nights) |
| Instrument | Two-meter Twin telescope (TTT) at Teide Observatory, Tenerife |
| Anti-tail | Sun-facing, antisolar tail observed |
| Jet wobble period | 7 hours 45 minutes |
| Nucleus rotation | About 15 hours 30 minutes per turn |
| Close solar approach | Oct. 30, 2025 – about 130 million miles (210 million km) |
| Closest Earth approach | Dec. 19 – about 168 million miles (270 million km) |
| Importance | Third known interstellar object; first observed outgassing in an interstellar comet |
For context, the study emphasizes that 3I/ATLAS offers a rare chance to study a pristine body formed around another star. The arXiv posting provides technical detail for researchers, while broader context can be found in credible outlets and official space agency resources.
External references: Space.com overview of 3I/ATLAS, arXiv preprint, NASA, ESA.
Evergreen Insights: Why 3I/ATLAS Matters
Interstellar visitors like 3I/ATLAS are rare messengers from other star systems. Each object offers a snapshot of planetary formation beyond our Sun and helps scientists test theories about composition, jet activity, and how such bodies respond to solar heating.
The sun-facing anti-tail observed in 3I/ATLAS challenges standard assumptions about how jets behave on comets, especially when the nucleus spins under intense solar radiation. Studying the jet precession helps researchers infer the nucleus’s shape, rotation state, and internal structure-key clues about its origin and history.
While 3I/ATLAS is now moving away from the inner solar system, its data will remain a touchstone for future interstellar visitors. The ongoing effort to characterize such objects informs telescope planning,mission design,and our understanding of how common-or rare-these cosmic travelers might be.
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