A New Study Confirms That the Interstellar Comet 3I/ATLAS May Be Older Than the Solar System
A New Study Confirms That the Interstellar Comet 3I/ATLAS May Be Older Than the Solar System
About a year ago, the interstellar comet 3I/ATLAS entered the inner Solar System, allowing for its detection (initially as A11pI3Z), and thus joined the two previously known interstellar objects (1I/'Oumuamua and 2I/Borisov). These kinds of objects are very interesting to scientists because they allow exploration of the Universe beyond the Solar System in ways different from those of telescopes.
Over time, a lot of data has been collected on the interstellar comet 3I/ATLAS, although its relatively modest size, high speed, and the inability to have prior warning of its arrival made it challenging to alter missions that were already launched (with other primary objectives) and dedicate telescope time for its observation. Nevertheless, global collaborative efforts have allowed for an understanding of the characteristics of this interstellar object, which currently has surpassed Jupiter's orbit and is about to enter the region of Saturn's orbit.
Interstellar Comet 3I/ATLAS: Investigations by the Very Large Telescope
A group of astronomers has used the Very Large Telescope (VLT) from ESO to analyze in detail the chemical composition of the interstellar comet 3I/ATLAS. The data has been included in the study titled High nitrogen and carbon isotopic ratios in the interstellar comet 3I/ATLAS, published recently in Nature Astronomy.
Thanks to the capabilities of the instruments at the scientific site, precise measurements of specific chemical fingerprints on the interstellar object were possible, the first of this kind conducted on a comet formed outside the Solar System.
According to reports, researchers discovered that the interstellar comet likely originated at the fringes of a very ancient stellar system, as previously hypothesized, which could be significantly older than the Sun itself. This finding opens new perspectives on the history of formation of the comet and similar objects that may visit our Solar System in the future.
Cyrielle Opitom from the University of Edinburgh stated, "Interstellar comets are icy bodies born around stars other than the Sun, which sometimes venture into our Solar System. They are like fossils of a planetary formation process that occurred far away, but we have the chance to study them from a much closer distance."
The unprecedented brightness of 3I/ATLAS allowed Opitom, Manfroid, and Hutsemékers (the other researchers involved in the study) to measure the isotopic ratios of the comet, i.e., the relative proportions among the different forms of the same chemical element. In particular, the UVES (Ultraviolet Visual Echelle Spectrograph) instrument installed on VLT was used to measure ratios among the isotopes of carbon and nitrogen present in the cyanide molecules detected in the gas enveloping the comet.
These ratios are considered an excellent indicator of a comet's origin, as they are very sensitive to the physical conditions of the environment in which they formed, and significant variations during the comet's long journey through space are not expected.
Aravind Krishnakumar, a researcher at the University of Liège, added, "Unlike comets from the Solar System, this interstellar visitor shows unusually high isotopic ratios of carbon and nitrogen."
The data collected from the VLT suggests that the comet formed in the outer regions of a planetary system around an ancient star with low metallicity (i.e., having few elements heavier than helium), typical of a still young Universe. For this reason, scientists hypothesize that 3I/ATLAS originates from a star much older than the Sun.
The study refers to a ratio of 151 between ¹²C/¹³C (with an uncertainty range of about 107 to 261) and a ratio of 363 between ¹⁴N/¹⁵N (with an uncertainty range of about 210 to 996). As mentioned above, both these values are higher than those of Solar System comets, where the ratios are usually about 90 and 150, respectively.
The study also specifies that the long stay of the comet in interstellar space (billions of years) may have chemically altered the surface layers due to cosmic rays, thus influencing the results. However, this effect may have been reduced since the measurements (between December 6 and December 26, 2025) occurred after the perihelion, when comet 3I/ATLAS had already shed part of its surface layers, exposing deeper and less altered material. Now that this object is moving away and will not return, future possibilities are looked at with the new **