A recently discovered interstellar comet, 3I/ATLAS, is causing a stir in the scientific community.
Most comets detected so far are local to our solar system, but 3I/ATLAS is a rare interstellar visitor. It was born in the deep reaches of space and will eventually leave, a temporary guest in our stellar home.
First spotted in July 2025, it’s just the third interstellar object ever discovered, after 1I/ʻOumuamua and 2I/Borisov.
Its arrival has sparked a conversation that sounds like something out of science fiction.
The nature of this new object has led Harvard’s Avi Loeb to speculate whether it could be extraterrestrial technology.
Loeb’s analysis suggests the object’s unique properties, like a possible “central light source” and a “fine-tuned trajectory,” could be evidence that an intelligent species sent it.
The mysterious light glow
In a recent blog post, Loeb analyzed a Hubble Space Telescope image of 3I/ATLAS, showing a light glow ahead of the object.
While this glow could be from evaporating dust, Loeb’s analysis suggests a different interpretation.
According to Loeb, the brightness of 3I/ATLAS appears to be coming from its core or some central source, not from surrounding dust.
He offers two possible explanations for this self-generated light. The first is that 3I/ATLAS is a rare, radioactive fragment from a supernova.
The second, more speculative, possibility is that the object is a nuclear-powered spacecraft, with the dust coming from its surface as it travels through space.
“The image shows a glow of light, likely from a coma, ahead of the motion of 3I/ATLAS towards the Sun. There is no evidence for a bright cometary tail in the opposite direction,” he writes.
“3I/ATLAS could be a spacecraft powered by nuclear energy, and the dust emitted from its frontal surface might be from dirt that accumulated on its surface during its interstellar travel. This cannot be ruled out, but requires better evidence to be viable,” he proposes in the blog post dated August 18.
He suggests this, combined with its “fine-tuned trajectory,” could point to a technological origin.
Furthermore, the Harvard scientist believes the data show that 3I/ATLAS is a similar size to the 1I/ʻOumuamua and 2I/Borisov.
It is just a bold claim right now
These are bold claims, and Loeb acknowledges that we need more evidence to prove them.
But his controversial ideas about these interstellar visitors have sparked widespread discussion and debate.
The scientist has a history of making controversial claims about objects from interstellar space.
He is well-known for his bold claim that the first interstellar object found, 1I/ʻOumuamua, was an alien technology, like a solar sail or a probe.
Loeb also led an expedition to recover what he claimed were fragments of an interstellar object from the Pacific Ocean floor.
On October 3, the new interstellar comet is set to make a close approach to Mars this fall, offering a unique chance for a closer look.
The Harvard astronomer suggested that NASA use its Mars Reconnaissance Orbiter (MRO) to observe the object with its scientific instruments.
The suggestion is to use MRO’s HiRISE camera to take pictures of 3I/ATLAS as it flies by. This could provide high-resolution data on the mysterious object.
“I encouraged the HiRISE team to use their camera during the first week of October 2025 in order to gather new data on 3I/ATLAS. They responded favorably,” he wrote in the blog.
According to Loeb, this is an excellent chance to observe the object because its closeness to the Sun will make it hard to see from Earth.