From the moment astronomers discovered interstellar object 3I/ATLAS, they became fixated on one question: What is it? Months of research have led to overwhelming scientific consensus that it is a comet from beyond our solar system, yet some still speculate that this cosmic visitor isn’t natural at all.
In July, shortly after the discovery, Harvard astronomer Avi Loeb and colleagues proposed that 3I/ATLAS could be an alien spacecraft. Even as studies have contradicted this hypothesis, Loeb has continued to suggest that 3I/ATLAS may be technological. To set the record straight, astronomers recently conducted a “technosignature search” of the interstellar object, essentially scanning it for artificial radio signals.
The study, which has yet to be peer reviewed, found “no credible detections of narrowband radio technosignatures originating from 3I/ATLAS.” In other words, the chances of this object being anything other than a comet are slim to none.
Silence from 3I/ATLAS
The Breakthrough Listen program conducted its technosignature search as 3I/ATLAS neared its closest point to Earth on December 18. Breakthrough Listen claims to be the largest ever scientific research program aimed at finding evidence of civilizations beyond Earth.
For this search, researchers used the Robert C. Byrd Green Bank Telescope (GBT) in Green Bank, West Virginia. This 328-foot (100-meter) steerable radio telescope is the largest moving structure on land. It’s a key asset to SETI (Search for Extraterrestrial Intelligence) research, using its extreme sensitivity to scan distant celestial objects for artificial radio signals.
“There is currently no evidence to suggest that [interstellar objects] are anything other than natural astrophysical objects,” the study authors wrote. “However, given the small number of such objects known (only three to date), and the plausibility of interstellar probes as a technosignature, thorough study is warranted.”
GBT scanned 3I/ATLAS from a distance of about 167 million miles (269 million kilometers), making observations that spanned four bands of the radio spectrum. At first, their search yielded 470,000 potentially artificial signals, but the researchers eliminated all but nine because they also appeared when the telescope pointed away from 3I/ATLAS. Those remaining candidates were later ruled out as human-made radio interference.
The researchers note that two other groups of researchers recently conducted their own technosignature searches of 3I/ATLAS at different frequencies, but they did not detect any credible artificial radio signals either.
More than just a comet
Extraterrestrial enthusiasts may find the results disappointing, but 3I/ATLAS’s natural origin does nothing to diminish the fact that it’s one of the most fascinating astronomical discoveries of our lifetime.
Detecting an interstellar object offers a rare opportunity to study a small-scale object from another star system. 3I/ATLAS is only the third one ever discovered, and over the past several months, astronomers have found evidence to suggest it’s vastly different from the two that came before it. This comet is significantly older, larger, and faster than its predecessors and exhibits unique chemical and physical properties.
3I/ATLAS is now heading back to interstellar space, but this won’t be the last time you hear about it. Astronomers will continue to analyze the mountain of data they gathered on this comet for years to come. These studies may not bring us closer to finding evidence of intelligent extraterrestrial life, but they will strengthen our understanding of distant star systems.