Prepare to question everything you thought you knew about comets. A groundbreaking new study on the interstellar object 3I/ATLAS has just dropped, and it’s challenging our understanding of these celestial bodies in ways we never anticipated. This 4-minute read will take you through the latest findings from the Keck II telescope in Hawaii, which observed 3I/ATLAS on August 24, 2025, when it was approximately 2.75 and 2.6 times the Earth-Sun distance from the Sun and Earth, respectively. But here’s where it gets controversial: the data reveals a puzzling anti-tail extension pointing toward the Sun, a feature that defies the behavior of all known comets, including the interstellar comet 2I/Borisov.
The Keck Cosmic Web Imager (KCWI) captured this anomaly in the wavelength range of 0.3425 to 0.55 micrometers, mirroring a similar observation by the Hubble Space Telescope in July 2025. But that’s not all—the gas plume around 3I/ATLAS shows a prominent nickel emission, yet there’s no trace of iron. This is bizarre because such nickel emissions, outside of 3I/ATLAS, are only known to occur in industrially produced nickel alloys through the carbonyl chemical pathway. The researchers boldly suggest that this process might be happening naturally near the nucleus of 3I/ATLAS, leading to a high concentration of nickel in that region.
A narrow-band KCWI image focusing on nickel (Ni) and cyanide (CN) emissions reveals another head-scratcher: nickel is more concentrated near the nucleus compared to cyanide, with emission radii of 600 kilometers for nickel and 840 kilometers for cyanide. And this is the part most people miss: the production rate of nickel relative to cyanide is significantly higher than in 2I/Borisov and far exceeds the median for solar system comets.
The emission profiles of both nickel and cyanide are asymmetric, extending both toward and away from the Sun, providing undeniable evidence of an anti-tail. Strangely, the white light image of 3I/ATLAS shows no typical cometary tail, which is expected from dust scattering sunlight and being pushed by solar radiation pressure. These anomalies further complicate the classification of 3I/ATLAS as a conventional comet. With each new piece of data, it seems to solidify its status as an outlier. Considering its seven previously documented anomalies, I maintain its ranking as 4 on the Loeb scale.
We’re eagerly awaiting the public release of images from the HiRISE camera on the Mars Reconnaissance Orbiter, captured on October 2, 2025, when 3I/ATLAS passed within 30 million kilometers of Mars. These images, with a pixel resolution of 30 kilometers, will offer a side view of the glow around 3I/ATLAS—three times sharper than our current best images from Keck and Hubble. Additional data will come from the Juice spacecraft in November 2025 and the Juno spacecraft in March 2026.
More high-quality data is exactly what we need to unravel the mysteries of 3I/ATLAS. Science thrives on evidence, not speculation, and this object is a perfect example of how the universe keeps surprising us.
Now, here’s the controversial question: Could 3I/ATLAS be something entirely different from what we’ve ever encountered? Or are we simply witnessing a natural process we don’t yet fully understand? Share your thoughts in the comments—let’s spark a discussion!
About the Author:
Avi Loeb, head of the Galileo Project and founding director of Harvard University’s Black Hole Initiative, is a renowned astrophysicist and bestselling author. His works include Extraterrestrial: The First Sign of Intelligent Life Beyond Earth and Interstellar, both of which explore the frontiers of cosmic discovery. Loeb’s unique perspective challenges us to think beyond conventional boundaries in our quest for knowledge.
