Scientists Trace 12-Billion-Year-Old Comet 3I/ATLAS to Ancient Low-Metallicity Star System
Updated
Updated · Sky at Night Magazine · Jul 6
Scientists Trace 12-Billion-Year-Old Comet 3I/ATLAS to Ancient Low-Metallicity Star System
3 articles · Updated · Sky at Night Magazine · Jul 6
Summary
VLT observations indicate interstellar comet 3I/ATLAS formed in the outer reaches of an old, low-metallicity star system, making it more than twice as old as the Sun and possibly up to 12 billion years old.
Carbon and nitrogen isotopic ratios measured in cyanide gas around the comet were unusually high compared with Solar System comets, giving researchers a chemical fingerprint of the environment where it formed.
3I/ATLAS is only the third interstellar object ever discovered, and its brightness allowed what scientists called the first such compositional measurements for a comet born outside the Solar System.
The comet is now passing through the Solar System and fading as it moves away from the Sun, limiting current observations while highlighting the role of the upcoming Extremely Large Telescope in studying future interstellar visitors.
This alien comet is older than our Sun. How does its strange chemistry challenge our fundamental understanding of how planets are born?
What secrets of a long-dead solar system does this 12-billion-year-old alien comet hold?
3I/ATLAS: First Detailed Isotopic Analysis of an Interstellar Comet Unveils Ancient, Metal-Poor Stellar Origins
Overview
The discovery of the interstellar comet 3I/ATLAS in July 2025 marked a pivotal moment in astronomy, as its exceptional brightness allowed scientists to make the first-ever detailed isotopic measurements of an object from beyond our solar system. This breakthrough provided a unique chance to analyze the precise chemical makeup of a comet formed in a different stellar system. As a result, 3I/ATLAS quickly became the focus of global observatories, ushering in new insights into the composition and origins of interstellar objects and opening a new era of astronomical research.