Webb finds clues to historic origin of Comet 3I/ATLAS

22/06/2026
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The third recognized interstellar comet in human historical past has a stunning chemical make-up, elevating questions as to how widespread, or uncommon, circumstances in our personal Solar System could also be.

As interstellar Comet 3I/ATLAS started transferring away from the Sun in December 2025, astronomers took the chance to show the highly effective NASA/ESA/CSA James Webb Space Telescope in its course and seize detailed measurements of its chemical elements. The comet was freshly warmed from its closest go by the Sun, and its historic ice had been transformed to a vivid coma of fuel superb for commentary.

Webb captured detailed knowledge, together with chemical ratios of carbon and deuterium, also referred to as heavy hydrogen, that aren’t present in Solar System comets. The outcomes shocked researchers. Working backward, astronomers used the elements that make up Comet 3I/ATLAS to know the surroundings during which it fashioned.

A paper detailing the findings was published on 22 June 2026 within the journal Nature.

The comet’s title comes from its standing because the third confirmed interstellar comet, which means it originated exterior the Solar System, and the telescope that first noticed it, the NASA-funded ATLAS (Asteroid Terrestrial-impact Last Alert System).

“This was a unique opportunity to study an ancient object from the distant Galaxy, probably pre-dating our Sun and Solar System,” mentioned astro-chemist Martin Cordiner of NASA’s Goddard Space Flight Center in Greenbelt, Maryland, and lead creator of the research. “On the one hand, we get direct insight into that distant time and place, and on the other, we learn something about how unusual our own Solar System may be.”

Cordiner and the analysis staff joined astronomers from many sub-disciplines in taking the chance to get a take a look at 3I/ATLAS on its journey by means of the Solar System. They acquired approval to interrupt Webb’s deliberate schedule of observations to utilize its NIRSpec (Near-Infrared Spectrograph) instrument to review the comet.

NIRSpec revealed exceptionally excessive ranges of deuterium, about 30 instances greater than seen in Solar System comets. This implies that 3I/ATLAS might have originated in a really chilly system a lot earlier within the historical past of our galaxy. During its formation, the fabric that grew to become integrated into 3I/ATLAS was doubtless uncovered to loads of radiation, however not any long-term heat that will have reprocessed its ‘heavy water’ ice, with deuterium, into the kind of H2O ice we’re accustomed to on Earth.

Additionally, NIRSpec confirmed solely traces of carbon-13 in comparison with lighter-weight carbon-12. This additionally factors to a really previous origin for 3I/ATLAS, as stellar programs turn out to be enriched with carbon-13 over time as generations of stars are born and die within the galaxy. That is why there are increased ranges of carbon-13 in our system, round our Sun, which fashioned comparatively not too long ago, 4.5 billion years in the past.

The analysis staff estimates that 3I/ATLAS may have fashioned so long as 10 to 12 billion years in the past, throughout the Universe’s ‘cosmic midday,’ when star formation was at its peak. Its younger origin system was doubtless ensconced in a comparatively chilly, dense cloud. The abundance of heavy water reveals that 3I/ATLAS spent its childhood in a deeply frozen state.

A separate study utilizing the European Southern Observatory’s Very Large Telescope, led by astronomer Cyrielle Opitom of the University of Edinburgh, enhances Webb’s findings with an evaluation of 3I/ATLAS’s carbon and nitrogen varieties within the type of the chemical cyanide.

“For us as scientists, finding these rare isotopes is fascinating, but the bigger picture here is looking at the possibilities of prebiotic chemistry elsewhere in the galaxy,” mentioned Stefanie Milam of NASA Goddard and co-author of the research with Cordiner. “So far, we know of only one place in the vast cosmos where chemical ingredients led to life – our Solar System, our Earth. Analysis of these interstellar objects is a major step towards learning how common, or uncommon, the conditions for the evolution of life are in the Universe.”

More data
Webb is the most important, strongest telescope ever launched into area. Under a global collaboration settlement, ESA supplied the telescope’s launch service, utilizing the Ariane 5 launch automobile. Working with companions, ESA was chargeable for the event and qualification of Ariane 5 diversifications for the Webb mission and for the procurement of the launch service by Arianespace. ESA additionally supplied the workhorse spectrograph NIRSpec and 50% of the mid-infrared instrument MIRI, which was designed and constructed by a consortium of nationally funded European Institutes (The MIRI European Consortium) in partnership with JPL and the University of Arizona.

Webb is a global partnership between NASA, ESA and the Canadian Space Agency (CSA).

Release on esawebb.org

Science paper

Release on NASA website

Contact:
ESA Media relations
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