And may a comet with its tail turned on the Sun be telling us more of the birth-places of worlds than any telescope ever told us? In Comet 3I/ATLAS, the third known interstellar, it is but the start of a chain of unusual phenomena that are currently being intensively studied by the whole universe of astronomers. Towards the end of 2025, the comet presented an anti-tail facing the Sun and clockwork jets, as well as the most delicate technosignature search of its type ever performed on a comet in interstellar.
1. Exploration and Path of a Unique Visitor
On July 1, 2025, C/2025 N1 was discovered by the ATLAS survey telescope in Chile, also known as 3I/ATLAS. The images made before discovery made its observation arc go further back in mid-June, proving to be on a hyperbolic trajectory, too fast to be bound to the Sun. It reached 1.4 AU of the Sun at the perihelion on October 30, 2025, and closest approach to Earth on the 19 December at 1.8 AUs. In March 2026, it will pass Jupiter and never enter the solar system again.
2. Virginians of the Rare Sunward Anti-Tail
The solar wind and solar radiation pressure drive most comet tails antisolar. In 3I/ATLAS, Hubble and Two-meter Twin Telescope (TTT) gave high-resolution views of a real physical anti-tail that stretched in the direction of the Sun, up to 1 million km. This geometry is due to anisotropic survival of dust: on the sunward side the sublimation of CO 2 raises large ice grains of H 2O, which last longer before evaporated. Survival lives are predicted to be the longest in solar direction as the Haser–Whipple model as the reason of the prominence of the anti-tail.
3. Rotation Period and Measurement of Wobbling Jets
In the anti-tail, Laplacian-filtered TTT images displayed narrow jets with a resonant position angle that varied by approximately 12 o Cp with a 7.74 0.35 hour oscillation. With this periodic modulation it suggests a nucleus rotation period of 15.48 yen error 0.70 the first time that a period of this kind was measured directly relative to the morphology of the jet in an interstellar comet. The source model is at +75o latitude with the active source ejecting dust of size microns and a velocity that is compatible with the CO 2-fueled drag of gases.
4. Coma Composition and Dust Properties
Spectroscopy indicates there is a CO 2-dominated volatile budget but the CO 2/H 2O ratio is significantly higher than the rate in the solar system, and contains volatiles that entrain large compact grains tens to hundreds of microns across. Polarimetric data indicates that there is a high negative branch of polarization, which is in line with mixed icy-dark particles. The mass and size of these grains account for the low antisolar tail and continuation of the sunward fan.
5. Co-ordinated Multi-Spacecraft Observations
NASA launched a multi-mission campaign involving Hubble, Webb, TESS, Swift, SPHEREx, and Mars spacecraft. On November 6, 2025, Europa Clipper observed 3I/ATLAS, at a distance of 102 million miles, with the Ultraviolet Spectrograph which detected hydrogen and oxygen as a result of water dissociation, and dust features. The JUICE spacecraft of ESA came with antisolar views. The geometry permitted the investigation of dust and ion tails when the telescopes on Earth were in the dark due to being close to the sun.
6. Technosignature Search of SETI and Breakthrough Listen
The 100-meter Green Bank Telescope had a scan of 3I/ATLAS on December 18, 2025, at 1-12 GHz with the capability of detecting isotropic transmitters down to 0.1 W, 100 times the power of a cell phone. Of the 471,000 first-time candidates, nine events were trimmed out, all caused by radio interference. No unnatural signals were found. Hydroxyl emission through natural photodissociation of water-related molecules was observed both by the Allen Telescope Array and MeerKAT, confirming that it was cometary and hydroxyl.
7. Ways to Precision the Observations
The detection of the weakly-spread jet structures demanded sophisticated image processing. The f/6 Ritchey-Chretien optics of 2.0-m f/6 TTT were used to obtain the resolution and sensitivity using a back-illuminated BEX2-DD CCD with Sloan-g+ filter. The Laplacian filtering of anisotropic features was made without any coma-symmetry and allowed correct position-angle measurements in non-static seeing. The UVS repurposing of Europa Clipper shows how planetary mission instrumentation can be applied to opportunistic comet science.
8. Interstellar Comet Science implication
The extraordinarily normal behavior of 3I/ATLAS, including jets, rotation and dust entrainment, provides an infrequent baseline of comparing the pristine interstellar substance with the comets of its solar system. With the next generation survey by the Vera C. Rubin Observatory, the number of interstellar objects detected yearly will rise up to one per decade with the potential of one per few months and statistical observations of rotation times, volatile compositions and tail structure of stellar populations.
The signal will fade as 3I/ATLAS moves out of its orbit to that of Jupiter in March 2026 and the study will come to an end. But the information that will be obtained you know, the geometry of its anti-tail down to the null finding in technosignature searching lights, will be used in cometary physics, interstellar object detection applications, and in future interception mission design over decades yet.
