A cosmic wanderer from another star system is revealing its secrets — and they’re more extraordinary than anyone expected. An international team of astronomers has captured the most detailed spectroscopic portrait yet of interstellar comet 3I/ATLAS using ESO’s Very Large Telescope (VLT). The observations uncovered glowing atomic nickel vapor — a rare and surprising signature that sets this visitor apart from typical Solar System comets. Just days ago, on December 27, 2025, Hubble released a stunning new image of the comet, showing dramatic twin jets streaming from its nucleus as it departs our system (source: NDTV/Hubble).
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| This image of the interstellar comet 3I/ATLAS was captured with Hubble’s Wide Field Camera 3 (WFC3) instrument on December 27, 2025. Image credit: NASA / ESA / CSA / Hubble. |
Discovered on July 1, 2025 by the NASA-funded ATLAS survey, 3I/ATLAS (also known as C/2025 N1) is only the third confirmed interstellar object to pass through our Solar System. Arriving from the direction of Sagittarius with a hyperbolic orbit (eccentricity 6.13), it offers a priceless glimpse into the chemistry of distant planetary systems.
Nickel Vapor at Vast Distances
Using VLT’s X-Shooter and UVES instruments, researchers observed the comet between July and August 2025 as it approached from 4.4 to 2.85 AU from the Sun. The coma appeared dust-dominated with a distinctive reddish hue, similar to primitive Kuiper Belt objects and suggesting organic-rich material.
As the comet warmed, scientists detected strong emission from cyanogen (CN) and numerous neutral nickel (Ni) lines — but notably no iron (Fe). Production rates of both species rose steeply toward the Sun, following power-law trends. This suggests low-energy release mechanisms like photon-stimulated desorption from dust grains rather than simple ice sublimation.
A Window to Alien Planetary Birthplaces
Interstellar comets preserve pristine material from their birth disks around other stars. Unlike ‘Oumuamua (rock-like) and 2I/Borisov (CO-rich), 3I/ATLAS is dust-heavy and shows decoupled nickel release — potentially the first clear case of organometallic or nanophase pathways in an extrasolar body.
The findings, published December 10, 2025 in The Astrophysical Journal Letters, turn nickel into a powerful tracer of extrasolar chemistry and Galactic origins.
Original source: Sci.News – VLT Reveals Detailed Spectral Portrait of 3I/ATLAS
Scientific paper: Rahatgaonkar et al. 2025. Very Large Telescope Observations of Interstellar Comet 3I/ATLAS. II. ApJL 995, L34; doi: 10.3847/2041-8213/ae1cbc