Astronomers Uncover the Pulsating Mystery of 3I/ATLAS

Astronomers have made a compelling discovery regarding the interstellar object known as 3I/ATLAS, first detected on July 1, 2025. Unlike typical asteroids, this object displays a unique rhythmic brightness that shifts every 16.16 hours, leading scientists to rethink their understanding of its characteristics and behavior. Initial observations suggested a rotating elongated nucleus, but further analysis indicates a more intricate phenomenon at play.

The light variability from 3I/ATLAS does not stem solely from the object’s shape. Observations from the Hubble Space Telescope on July 21, 2025 revealed a glowing coma surrounding the nucleus, rather than a solid core that reflects light. This coma, a halo of gas and dust, complicates measurements of the object’s size and luminosity. While the nucleus is likely much smaller than initially assumed, its contribution to the overall light output is minimal.

If one considers a solid surface with a typical albedo of 4-5%, the mathematics would suggest a radius of 10 kilometers in visible light or up to 23 kilometers at a wavelength of 1 micrometer. However, the findings indicate that the effective radius of the nucleus is approximately 2.8 kilometers, meaning it reflects less than one percent of the total light at that wavelength. This raises intriguing questions about the pulsating light observed.

The periodicity of 3I/ATLAS is not necessarily due to the shape of its nucleus, but likely linked to jet activity observed over recent weeks. Images from November 30, 2025, captured complex jet formations emanating from the rotating nucleus. If these jets release material in a pulsed manner rather than continuously, the coma would exhibit periodic brightness variations corresponding to these eruptions.

As the object rotates, pockets of ice on the nucleus can warm up and release gas and dust, creating bursts that increase the coma’s brightness. This process resembles a heartbeat, with each pulse acting as a stream of material circulating through the coma. The estimated outflow velocity of 440 meters per second means sublimated volatiles can travel significant distances, up to 25,600 kilometers during one complete rotation.

Despite the striking nature of these findings, the lack of systematic observations over multiple days has left many questions unanswered. Without a series of calibrated images, the origin of the pulsing jets remains speculative. If 3I/ATLAS were a technological object, its jets might not align with the Sun, complicating the interpretation of the observed activity.

The reported periodicity of 16.16 hours highlights a fascinating complexity in understanding this interstellar object. As research continues, astronomers aim to gather more data to clarify the nature of 3I/ATLAS and its mysterious behavior, potentially unlocking further secrets of the cosmos.