A comet shouldn’t have a heartbeat. Yet NASA’s latest images of the interstellar object 3I/ATLAS detail just that: jets of gas and dust brightening and dimming in an exact rhythm once every 16.16 hours, a phenomenon which has sparked both scientific intrigue and public speculation as to its nature.
3I/ATLAS was first detected by the Asteroid Terrestrial-impact Last Alert System survey telescope in Chile on July 1, 2025, and is only the third confirmed interstellar visitor to our solar system. Coming in from the direction of the constellation Sagittarius at speeds over 130,000 miles per hour, its hyperbolic trajectory ensures it will never return once it departs. NASA’s early observations showed cometary activity in the form of coma formation and tail development; since then, data have shown anomalies that no natural comet has ever demonstrated.
On November 14, 2025, astronomers recorded a narrow-band absorption signature at precisely 1665 and 1667 MHz, frequencies associated with the 18-centimeter OH microwave transition long considered by SETI researchers as a possible interstellar communication channel. This was a clean, selective signal, unlike the broadband thermal noise characteristic of cometary outgassing; it is rarely produced under natural conditions. Two weeks later, high-resolution imagery disclosed the pulsing jet structure-material streaming outward in bursts at 440 meters per second, each burst carrying volatiles roughly 25,600 kilometers before the next pulse.
Avi Loeb, an astrophysicist at Harvard, interprets the phenomenon as a kind of “heartbeat.” In this case, the periodic brightening was first mistaken for rotational variability of the nucleus. The latter, however, estimated by Hubble data to be as small as 32020 meters across, does not account for the tens-of-percentage amplitude in observed total light output. Instead, the source is the jets themselves, whose orientation appears remarkably stable relative to background stars, defying expected bending from solar radiation and rotational dynamics.
Such stability, together with the narrow-band radio anomaly, has suggested to some researchers that the two may be related. A timed propulsion or maneuvering cycle could account for both the periodic mass ejection and the modulation of OH-rich materials surrounding the object, through which the absorption lines are produced. In natural comets, jets are a generally direct response to solar heating; they erupt chaotically as ice pockets rotate into sunlight. In 3I/ATLAS, the persistence of the jets in fixed orientation suggests an internal mechanism firing independently of solar geometry.
NASA’s imagery campaign has drawn on everything from the Hubble Space Telescope to the Mars Reconnaissance Orbiter, which snapped the comet 19 million miles away during its October 2, 2025, Mars flyby. The European Space Agency’s JUICE spacecraft also observed 3I/ATLAS between November 2 and 25, recording its coma and dual tails-one of charged gas, one of dust-while the comet was in a highly active state after its October 30 perihelion at 1.4 AU from the Sun.
The origin of the heartbeat pattern is a subject of active investigation. In a natural scenario, it could be due to a sunward jet activated only when a particular ice-rich region faces the Sun, pumping the coma periodically. But if the jet’s orientation is arbitrary and not aligned with the Sun, then the possibility of a technological source gains significant credence. As Loeb mentioned, “A movie showing the periodic brightening of the jets… can reveal whether the jets are natural or technology-based on the orientation of the heartbeat pattern relative to the Sun.”
While NASA officials, including Acting Administrator Sean Duffy, have publicly dismissed the idea of alien spacecraft-stating “No aliens. No threat to life here on Earth”-the combination of narrow-frequency radio behavior and mechanically timed jets is unprecedented in cometary science. Its December 19 closest approach, at about 170 million miles from Earth, offers a critical window for coordinated observations. If the radio absorption and jet pulsations rise and fall in perfect synchrony, it could mark the strongest evidence yet that 3I/ATLAS is not behaving like a comet at all, but like a device crossing our solar system from another star.
