As if interstellar visitors weren’t unsettling enough, 3I/ATLAS has now developed what appears to be a 16.16-hour “heartbeat.” The object’s brightness rises and falls with such steady rhythm that even seasoned astronomers are having the scientific equivalent of an eyebrow-raise.
Harvard astrophysicist Avi Loeb — who has become something of an expert in unexpected space behaviour — says the pulse looks oddly deliberate. “The puffs are periodic, like the blood stream of a heartbeat,” he said. This is not the sort of sentence astronomers enjoy hearing before coffee.
Why A Comet Might Be Flashing Like A Beacon
Observations published over the summer revealed ATLAS brightens and dims like clockwork. Researchers initially blamed the nucleus, but that explanation didn’t get very far; less than ten per cent of the light comes from there.
Most of the glow is produced by the comet’s coma, the cloud of dust and gas that surrounds it, which means the rhythmic blinking must come from jets inside the coma itself. Think of it as a cosmic fog machine that refuses to operate on anything but a strict schedule.
Loeb suggested the pulses could come from repeating bursts of gas: “The pulses could be periodic thrusts for orbit corrections or some other internal cycle within the spacecraft.”
Spacecraft. Yes. That word again.
Natural Process… Or A Bit Too Neat?
If ATLAS were a perfectly normal comet (which, to be fair, it has shown very little interest in being), the pulse could come from a sunlit ice pocket that vents gas whenever it rotates into view. In that scenario, the coma would periodically swell like a balloon being squeezed by a toddler.
But if the pulse has nothing to do with the Sun’s position, the explanation becomes less cosy. Regular, timed jets could imply a mechanism operating for reasons other than “I am icy and stressed.”
Because why wouldn’t an interstellar object also behave like it’s running its own internal maintenance cycle?
The Jupiter Detour
To complicate things further, ATLAS appears to be heading towards Jupiter with suspicious precision, arriving in March. Loeb has floated the idea that it might be dropping off “satellites” to gather information — a theory which, if true, would certainly give Jupiter something new to worry about.
He even suggested the object may have fine-tuned its path using artificial thrusts during its closest approach to the Sun. In fairness, comets often behave wildly near perihelion; they just don’t usually give the impression they’re reading the manual while doing it.
NASA: Please Relax, It Is Still A Comet
NASA, displaying impressive levels of calm, maintains that 3I/ATLAS is a comet, full stop. Weird? Yes. Active? Definitely. Planning anything? Unlikely, according to the agency’s official line.
Still, with ATLAS drawing closer to Earth in the days ahead, scientists will be watching closely — partly for valuable data, and partly to confirm that the cosmic heartbeat doesn’t start spelling out messages.
Published by Kerry Harrison
Kerry’s been writing professionally for over 14 years, after graduating with a First Class Honours Degree in Multimedia Journalism from Canterbury Christ Church University. She joined Orbital Today in 2022. She covers everything from UK launch updates to how the wider space ecosystem is evolving. She enjoys digging into the detail and explaining complex topics in a way that feels straightforward. Before writing about space, Kerry spent years working with cybersecurity companies. She’s written a lot about threat intelligence, data protection, and how cyber and space are increasingly overlapping, whether that’s satellite security or national defence. With a strong background in tech writing, she’s used to making tricky, technical subjects more approachable. That mix of innovation, complexity, and real-world impact is what keeps her interested in the space sector.