Scientists have determined the age of the interstellar comet 3I/ATLAS, revealing it is likely around three times older than Earth. The comet, which passed through our solar system late last year, sparked initial concerns of an alien invasion before NASA confirmed it as a natural celestial object. While its status as a comet was clear, its composition and age remained unknown until astronomers utilized the European Southern Observatory's Very Large Telescope (VLT) for analysis.
According to the study, 3I/ATLAS appears to have originated from the outskirts of an ancient star system. Researchers measured the ratios of carbon and nitrogen isotopes within cyanide molecules in the gas surrounding the comet. These ratios are considered strong indicators of a comet's birthplace. The analysis revealed unusually high carbon and nitrogen isotopic ratios, distinguishing it from comets originating within our solar system.
This discovery suggests that 3I/ATLAS formed around a star with a low-metallicity, meaning it contains fewer elements heavier than helium. Such stars are believed to have formed early in the universe's history, when it was less chemically developed. Therefore, the comet likely predates our own Sun and solar system significantly.
"The field of interstellar objects is still very new, and we do not really know what to expect. Every time a new one is discovered, we have new surprises," said Cyrielle Opitom, a researcher at the University of Edinburgh. Co-author Rosemary Dorsey of the University of Helsinki added, "3I/ATLAS is a really exciting opportunity to probe the composition of another planetary system, one that formed long before our Sun and Solar System even existed."
3I/ATLAS is only the third interstellar object ever identified, following 1I/ʻOumuamua in 2017 and 2I/Borisov in 2019. Its relative brightness allowed for a more detailed compositional analysis than was possible with the previous two objects, which were too faint to study effectively.
As 3I/ATLAS continues to move away from the Sun, it is becoming fainter, and opportunities for observation with the VLT are diminishing. The European Southern Observatory is developing the Extremely Large Telescope (ELT), which may offer future possibilities for studying such interstellar visitors.