The universe occasionally sends us guests from beyond our own solar neighborhood. Interstellar Comet 3I/ATLAS is one such object, now on its long journey back out into deep space. Scientists from the Indian Space Research Organisation (ISRO)’s Physical Research Laboratory (PRL) have made crucial ground-based observations that reveal the chemical composition and activity level of this fascinating cosmic traveler.
Tracking the Interstellar Visitor.
Interstellar objects like 3I/ATLAS are invaluable, offering a rare glimpse into the material makeup of other star systems. Comets are essentially frozen time capsules, and studying an interstellar one provides direct clues about the conditions and processes in stellar nurseries far away from our Sun.
The comet 3I/ATLAS was observed by the PRL team while it was on its way out of the inner solar system following its perihelion passage (closest approach to the Sun). The observations were made between November 12-15, 2025.
ISRO’s Eye on the Sky: The Mount Abu Observations.
The critical data was collected using the PRL 1.2-meter telescope at the Mount Abu Infrared Observatory in Rajasthan. This high-altitude facility is a cornerstone of Indian astronomical research.
The scientists employed two primary observational modes:
- Imaging: To capture the physical structure of the comet.
- Spectroscopy: To analyze the constituent wavelengths of light emitted from the coma, revealing its chemical composition.
The images clearly showed a distinct, near-circular coma —the huge, glowing atmosphere of gas and dust that forms around the comet’s nucleus as solar heat causes the frozen ices to vaporize.
Unmasking the Comet: Key Scientific Findings.
The spectroscopic analysis delivered the most surprising and significant results regarding the nature of 3I/ATLAS.
A. Chemical Fingerprint: CN, C2, and C3.
The spectrum of light from the comet showed prominent emission features belonging to molecules commonly seen in comets originating from our own solar system:
- Cyanogen (CN)
- Diatomic Carbon (C_2)
- Triatomic Carbon (C_3)
The presence of these bands suggests a chemical composition that is not wildly different from the comets born in the Oort cloud surrounding the Sun.
B. Activity Level: The ‘Production Rate’.
The scientists calculated the production rate—the rate at which gas sublimates from the nucleus into the coma, which is a measure of the comet’s activity level.
- The production rates for the prominent molecular bands were computed to be around 10^{25} molecules per second.
Crucially, when the ratios of these production rates were compared, Comet 3I/ATLAS fell squarely into the class of ‘typical comets’ of the solar system.
The Big Takeaway.
The finding that an interstellar comet shares a similar chemical makeup and activity profile to solar system comets is profound. It suggests that the basic processes of cometary formation—the ingredients available and the conditions under which they freeze—may be remarkably consistent across vast interstellar distances, reinforcing the idea that our solar system may not be unique in its chemical building blocks.
Further observations of this special traveler will continue as it fades into the darker reaches of the night, providing more data to confirm if 3I/ATLAS is truly a ‘typical’ example of cosmic wanderers.