Space Radiation Reshaped Comet 3I/ATLAS, Webb Data Shows

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The interstellar comet 3I/ATLAS was spotted traversing the solar system on Aug. 27 by the Gemini South observatory in Chile. (Image credit: International Gemini Observatory/NOIRLab/NSF/AURA/Shadow the ScientistImage Processing: J. Miller & M. Rodriguez (International Gemini Observatory/NSF NOIRLab), T.A. Rector (University of Alaska Anchorage/NSF NOIRLab), M. Zamani (NSF NOIRLab))

Recent research employing observations from the James Webb Space Telescope (JWST) has indicated that Comet 3I/ATLAS is exceedingly bombarded due to billions of years of cosmic ray exposure.

The new research implies that during its interstellar journey through the Milky Way, the comet has absorbed such a large quantity of cosmic rays from the galaxy that it has formed a highly irradiated shell that no longer mirrors the substance of its original star system.

With the aid of JWST observations and computational models, scientists have inferred that the comet’s previously recorded “extreme” quantities of carbon dioxide (CO2) enrichment originate from space radiation accumulated across its roughly 7-billion-year existence, as per the study published on the preprint repository arXiv on Friday (Oct. 31). These conclusions have not been formally reviewed by other experts.

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Galactic cosmic rays — a form of space radiation composed of energetic particles originating outside the solar system — bombard carbon monoxide (CO) in space, changing it into carbon dioxide (CO2). Within our solar system, the heliosphere — the vast radiation zone discharged by the sun — offers protection to Earth and surrounding planets against the majority of this cosmic radiation. However, in interstellar space, where 3I/ATLAS has spent much of its existence, such shielding does not exist.

The authors of the recent study have determined that over a period of billions of years, the physical state of comet 3I/ATLAS’s ice has been greatly modified by cosmic rays, penetrating to a depth of approximately 50 to 65 feet (15 to 20 meters).

“It occurs gradually, but across vast stretches of time, it has a very substantial effect,” stated study leader Romain Maggiolo, a research scientist at the Royal Belgian Institute for Space Aeronomy, when interviewed by Live Science.

These results, which researchers have portrayed as a “change in perspective” for the investigation of interstellar objects, imply that bodies similar to comet 3I/ATLAS are primarily formed from material treated by galactic cosmic rays, rather than untouched matter indicative of their formation environments.

In simple terms, comet 3I/ATLAS has essentially become a consequence of its interstellar travels, instead of being representative of its place of origin — at least on the surface.

Tracking the interstellar visitor

Currently, Comet 3I/ATLAS is orbiting the sun. The comet made its closest approach to the sun, known as perihelion, on Thursday (Oct. 29). Comets undergo warming as they move closer to stars, resulting in the sublimation of surface ices into gas. The latest findings suggest that prior to perihelion, any gases expelled from the comet originated solely from its irradiated outer layer. This pattern is anticipated to persist after perihelion. However, Maggiolo suggested that, although improbable, solar erosion could potentially be intense enough to reveal the unaltered materials from the comet’s native star, which are enclosed within its nucleus.

“It will prove highly valuable to assess observations both before perihelion — specifically, the initial observation recorded upon its arrival in the solar system — and after perihelion, once some erosion has taken place,” Maggiolo explained. “By analyzing these variations, we might gain insights into its initial composition.”

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The research team modeled the total effect of galactic cosmic ray exposure on the structure and chemical make-up of ice over a span of 1 billion years of radiation exposure. This method makes use of laboratory simulations replicating the outcomes of galactic cosmic rays, which may not entirely reflect the conditions present in interstellar settings. Nevertheless, the tests present a reliable indicator of the situations experienced by comets during their isolated, multi-billion-year travels throughout interstellar space, as explained in the study.

The results of the simulations suggested that 1 billion years of radiation exposure was adequate for comet 3I/ATLAS to develop its heavily irradiated surface layer. Maggiolo indicated that comet 3I/ATLAS still offers a wealth of intriguing information, although it has changed and aged. Researchers must consider these aspects during their investigations.

“We need to proceed with caution and consider aging processes, which increases the workload for researchers, but [3I/ATLAS] continues to be highly engaging,” Maggiolo stated.

TOPICS3I/ATLAS

Patrick PesterSocial Links NavigationTrending News Writer

Patrick Pester acts as the writer covering trending news at Live Science. His writing has been featured on various other scientific websites, including BBC Science Focus and Scientific American. Patrick transitioned into journalism following a prior career spent working in zoos and wildlife preservation. He received the Master’s Excellence Scholarship to study at Cardiff University, where he earned a master’s degree in international journalism. He also holds a second master’s degree in biodiversity, evolution, and conservation in action from Middlesex University London. When not engaged in writing news, Patrick delves into the commerce of human remains.

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