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Researchers make new discovery about the interstellar comet 3I/ATLAS: it was born in extreme cold, has a high concentration of deuterium, is the oldest interstellar visitor ever detected, and may reveal what the Universe was like right after the Big Bang.

Written by Ruth Rodrigues
Published on 28/04/2026 at 11:01
Updated on 28/04/2026 at 11:02
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Nature Astronomy research identifies that the interstellar comet 3I/ATLAS was born in extreme cold and has a high concentration of deuterium. Learn all about the visitor.

A study published in the journal Nature Astronomy last Thursday (23) brought surprising revelations about comet 3I/ATLAS, the third interstellar visitor confirmed by science.

Using the ALMA observatory in Chile, scientists from the University of Michigan discovered that the object may have formed in a zone of extreme cold and isolation in the Milky Way, possibly even before the birth of its parent star.

With an estimated age of 11 billion years, the comet is considered a “time capsule” that preserves secrets from the first billion years after the Big Bang.

Comet 3I/ATLAS: The chemical signature of a remote past

The uniqueness of comet 3I/ATLAS lies primarily in the state of preservation of its original chemistry. Through remote observations, scientists identified surprisingly high levels of deuterium — known as the “heavy” isotope of hydrogen.

This chemical signature acts as a cosmic thermometer: the high concentration of the element indicates that the celestial body formed under extreme cold, surpassing the low temperatures of our own Solar System.

This finding supports the theory that the “nursery” of this comet was an isolated environment, shielded from the heat of other stars. Since deuterium is scarce in our galactic neighborhood, 3I/ATLAS serves as a rare physical record of scenarios that existed billions of years before the Sun’s emergence.

Unlike comets that orbit the Sun periodically, comet 3I/ATLAS is a fleeting traveler. It joins asteroid 1I/’Oumuamua (2017) and comet 2I/Borisov (2019) as the only intruders from other stellar systems ever detected.

However, 3I/ATLAS stands out due to its antiquity, being more than twice the age of our Solar System.

Check out the technical data of the object:

  • Estimated age: About 11 billion years.
  • Nucleus size: Between 440 meters and 5.6 kilometers (according to Hubble data).
  • Exit speed: Approximately 220,000 km/h.
  • Trajectory: Has already passed Jupiter and is leaving the Solar System.

The journey through the Solar System and goodbye

The discovery of the comet occurred in July of last year, allowing agencies like NASA and ESA to coordinate global observations. During its brief stay, comet 3I/ATLAS crossed Mars’ orbit and reached its closest approach to Earth in December. Currently, the visitor has already begun its definitive exit trajectory.

According to astronomer Teresa Paneque-Carreno, co-author of the study, the exact birthplace of the comet remains a mystery, but its existence proves that valuable information about primordial planetary formation is wandering through deep space.

Conceptual illustration of the interstellar comet 3I/ATLAS, highlighting the presence of deuterium-containing water molecules (HDO). Credits: NSF/AUI/NSF NRAO/M. Weiss

As it is moving away at high speed, the object can now only be tracked by highly sensitive telescopes. The study of comet 3I/ATLAS is not just an astronomical curiosity, but an opportunity to observe chemical processes that occurred when the Universe was young.

The detection of substances such as “interstellar alcohol” and deuterium-rich water offers clues about how the fundamental building blocks of matter were organized in the primitive phases of the cosmos. Thus, as 3I/ATLAS heads into the darkness of intergalactic space, it leaves behind a database that will help recalibrate theories about the evolution of galaxies.

The understanding that such ancient objects can survive millennia-long journeys through the vacuum paves the way for future interception missions, which will seek to unravel the history of the Milky Way without us having to leave our own stellar system.

Source: Olhar Digital

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Ruth Rodrigues

Formada em Ciências Biológicas pela Universidade do Estado do Rio Grande do Norte (UERN), atua como redatora e divulgadora científica.

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