Mysterious Interstellar Object Has Sprouted a Tendril Reaching Toward the SunVictor Tangermann
FuturismMon, October 20, 2025 at 1:40 PM EDT
3 min read
Keck II telescope observations of interstellar object 3I/ATLAS found "evidence for a puzzling anti-tail extension" pointing at the Sun.Interstellar object 3I/ATLAS continues to fascinate astronomers as it rips through our solar system. And the more we find out about the object — widely suspected to be an icy comet — the more questions emerge.
Latest among those mysteries: the Keck II telescope in Hawaii observed the object when it was just over 2.5 times the distance between the Earth and Sun back in August, and found “evidence for a puzzling anti-tail extension in the direction of the Sun,” as Harvard astronomer Avi Loeb wrote in a blog post last week.
In a recent paper that has yet to be peer reviewed, a team of astronomers used the Keck data to confirm “previously reported cyanide and nickel outgassing,” which are being emitted both in and against the direction of the Sun, which offers “clear evidence for an anti-tail,” according to Loeb.
“Most remarkably, the white light image of 3I/ATLAS does not show evidence for a familiar cometary tail, as expected for dust which scatters sunlight and is pushed away from the Sun by solar radiation pressure,” he added.
As IFLScience explains, the phenomenon could be the result of natural processes. One possibility is that it’s a type of optical illusion; because of the Earth’s relative location in space, a comet’s wide tail can fan out from behind it to make it look as if it has a tail growing tail sprouting from either side.
Another possibility is that larger grains of dust are refusing to be pushed away by solar wind on the comet’s Sun-facing side. The comet’s core of sublimating ice could be spinning rapidly and releasing large pieces of debris in both directions along its orbit making it appear to have a Sunward “anti-tail” in addition to its regular tail.
Scientists have previously identified other comets showing Sun-facing “anti-tails” that suggest the “slow ejection of relatively large dust particles predominantly from the sunlit hemisphere.”
“With a rotating comet nucleus… ejecta from a spot can come off with heliocentric velocity that puts it either in front of or behind the nucleus,” explained University of California, Los Angeles planetary astronomer Michael Busch in a post on Bluesky. “It does not matter which side it starts from.”
“Small dust and ejected gas gets pushed out by radiation pressure and solar wind,” he explained in a followup. “But larger pieces of ejecta spread out along the orbit; both in front of and behind the nucleus.”
To Loeb, the anti-tail remains an “anomaly that raises two questions,” according to a more recent blog post. “What is the nature of the anti-tail? Why are comet experts ignoring this anomaly while insisting that 3I/ATLAS is a familiar comet?”
Fortunately, before 3I/ATLAS leaves the solar system for good, it will provide us with several more opportunities to examine it. It’s expected to make a close approach Jupiter next month, giving NASA’s Juno spacecraft and the European Space Agency’s Juice spacecraft a chance to get a brief glimpse.
For now, Loeb ranks 3I/ATLAS as a four out of ten on his “Loeb scale” — which he invented to gauge the likeliness of an interstellar object being extraterrestrial technology — in a figure that he says means that it has “increasingly anomalous characteristics.”
https://www.yahoo.com/news/articles/mysterious-interstellar-object-sprouted-tendril-174022865.html
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