The interstellar comet 3I/ATLAS likely originated from a low-metallicity star system more than twice as old as the Sun, according to research published in Nature Astronomy. An international team using the European Southern Observatory’s (ESO) Very Large Telescope (VLT) identified unusually high carbon and nitrogen isotopic ratios in the comet’s gas, signaling a formation environment vastly different from our own Solar System.
How did scientists determine 3I/ATLAS is older than the Sun?
Researchers measured the “chemical fingerprints” of the comet by analyzing isotopic ratios—the relative amounts of different forms of the same element. Using the UVES instrument on the VLT, the team specifically targeted cyanide molecules in the gas surrounding the comet.
Dr. Aravind Krishnakumar, a researcher at the University of Liège and study co-author, stated that 3I/ATLAS carries carbon and nitrogen isotopic ratios that are unusually high compared to comets from our Solar System. Because these ratios are sensitive to the physical conditions of the formation environment and do not change significantly during space travel, they serve as a reliable indicator of origin.
What does “low-metallicity” tell us about the comet’s home?
The findings indicate the comet formed in the outer regions of a low-metallicity star. In astronomical terms, a low-metallicity star contains very few elements heavier than helium. According to the study, such stars typically formed when the Universe was much younger and less chemically rich.
Dr. Rosemary Dorsey, a researcher at the University of Helsinki and UC alumni, noted that 3I/ATLAS provides a way to probe a planetary system that existed long before our own. This evidence suggests the comet is a “fossil” from a distant planetary formation process.
How does the VLT data compare to James Webb Telescope findings?
The VLT findings align with a separate study led by Dr. Martin Cordiner at the NASA Goddard Space Flight Center, published in Nature. While the VLT team focused on cyanide molecules, Cordiner’s team used the James Webb Space Telescope to find similar carbon isotopic ratios and elevated levels of deuterium, also known as heavy hydrogen.
| Instrument | Key Finding | Source/Lead |
|---|---|---|
| ESO Very Large Telescope (VLT) | High Carbon/Nitrogen isotopes in cyanide | Dr. Cyrielle Opitom et al. |
| James Webb Space Telescope | Elevated deuterium and carbon ratios | Dr. Martin Cordiner (NASA) |
What happens next for interstellar object research?
As 3I/ATLAS moves away from the Sun, it is becoming too faint for further VLT observations. However, the European Southern Observatory is preparing the Extremely Large Telescope (ELT), which will be capable of performing similar chemical measurements on future interstellar visitors, even those that are significantly dimmer than 3I/ATLAS.
Dr. Cyrielle Opitom, a researcher at the University of Edinburgh who led the study, says the field is still very new and every new discovery brings surprises.
Frequently Asked Questions
What is an interstellar comet?
According to the research team, these are icy objects formed around a star other than the Sun that occasionally wander into our Solar System.
Why was 3I/ATLAS easier to study than 1I/ʻOumuamua?
Astronomers did not detect gas in 1I/ʻOumuamua, and the second object, 2I/Borisov, was too faint. 3I/ATLAS possessed unprecedented brightness, allowing for isotopic measurements.
How much older is 3I/ATLAS than the Sun?
Evidence from the combined studies suggests the comet is more than twice as old as the Sun.
Do you think we will find more objects from ancient star systems? Share your thoughts in the comments below or subscribe to our newsletter for the latest in deep-space exploration.
