This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: UK astronomers have uncovered new clues about the origin of 3I/ATLAS—only the third known object from beyond the solar system ever spotted. In a new paper published in Monthly Notices of the Royal Astronomical Society, researchers reveal that the comet formed in extremely cold conditions, far from any star.
Lea Ferellec, a research fellow based in Northumbria University's School of Engineering, Physics and Mathematics, led the study, which looked at the ionized gases streaming off 3I/ATLAS as it moved away from the sun. The observations were obtained using the Large Integral Field Unit (LIFU) mode of a new instrument, the WHT Enhanced Area Velocity Explorer (WEAVE), developed with the support of the Science and Technology Facilities Council (STFC) and installed on the Isaac Newton Group's 4.2-meter William Herschel Telescope. By combining WEAVE's LIFU imaging spectroscopy with the WHT's new non-sidereal guiding capabilities, the team identified five different ions in the comet's stream simultaneously.
This is a rare achievement for any comet and a remarkable first for an interstellar object of this nature. By measuring how much dinitrogen gas was present compared with carbon monoxide, the researchers worked out that 3I/ATLAS formed somewhere extremely cold, likely colder than -240°C (-400°F). This suggests it formed a long way from its home star, in the outer, icier edges of wherever its solar system took shape.
Speaking about the findings, Ferellec said, "This object gives us a rare chance to study material that formed somewhere completely different from our own solar system. "Finding that it's so rich in nitrogen tells us it likely formed in extremely cold conditions, far from its home star. "Every one of these objects we study helps us understand a little more about how planets form around other stars." Every so often, a large icy rock, similar to a comet, arrives from beyond our solar system, having formed around a different star entirely, then traveling for millions of years before reaching us.
These are called interstellar objects, and only three have ever been spotted. The most recent is 3I/ATLAS, which was discovered in July 2025 as it sped past the sun and back out into deep space. Because these objects formed in a completely different part of the galaxy, studying them gives scientists a rare glimpse into how planets and comets form around other stars, not just our own.
The team, which included researchers from the University of Edinburgh, also looked at how the ions changed the farther they traveled along 3I/ATLAS's tail, which forms when plasma streaming from the sun sweeps the object's charged particles out behind it. This is the first time this level of detail has been captured for an object of this kind. "Powerful, large-format IFUs with high sensitivity in the blue optical spectrum—like WEAVE-LIFU on the WHT—are opening new frontiers for the study of comets and other solar system objects," said ING Director Rubén Sánchez-Janssen.
Extract — continue reading at the source.
