MeerKAT Unveils Celestial Mysteries
The South African radio interferometer MeerKAT, a sophisticated network of 64 antennas each 13.5 meters in diameter, has recently detected radio lines of the hydroxyl radical OH at frequencies 1665 and 1667 MHz from the interstellar comet 3I/ATLAS. These radio signals, far from artificial spacecraft transmissions, represent a natural ‘radio signature’ associated with the sublimation of ice and the formation of a gaseous envelope around the comet’s nucleus. This observation highlights MeerKAT’s exceptional capability in tracking elusive celestial phenomena.
The Science Behind the Signals
The hydroxyl radical OH forms when the Sun’s ultraviolet radiation breaks down water molecules in the comet’s substance. These atoms and molecules can absorb or emit radio waves at specific frequencies. Astronomers have long utilized these OH lines to trace water distribution and related processes in nebulae, star formation regions, and comets. In this instance, MeerKAT registered the OH in absorption lines, a phenomenon explained by the geometry of observations and the comet’s close angular proximity to the Sun. This area of its trajectory favors absorption over emission at these frequencies. Such behavior is consistent with typical comet activities as they approach the Sun, where ice sublimates vigorously, and the radiation flow increases, affecting the comet’s trajectory due to the reactive forces of gases.
Attempts and Achievements
MeerKAT’s observations came after a series of unsuccessful attempts. The radio telescope failed to secure signals from 3I/ATLAS on September 20 and 28. However, the successful detection of OH-absorption occurred on October 24-five days before the comet reached its perihelion, the orbital point closest to the Sun. As of the publication date, no other radio signals apart from OH lines have been reported.
Interstellar Curiosities
Astrophysicist Avi Loeb, a notable proponent of the theory regarding the potential technological origins of interstellar objects, drew particular attention to 3I/ATLAS. Earlier, he advised radio telescopes, including MeerKAT, to scan for artificial signals, noting that 3I/ATLAS’s arrival direction deviated by less than nine degrees from the direction of the famous 1977 Wow! signal at 1.4204556 GHz. Despite the absence of artificial signals, Loeb continues to urge further examination. According to his data, on March 16, 2026, 3I/ATLAS will pass approximately 53 million kilometers from Jupiter, where the Juno spacecraft with its dipole antenna will search for low-frequency radio signals from the object in the 50 Hz-40 MHz range.
Future Prospects
Additionally, it has been suggested to monitor whether the formation speed of OH remains constant or changes, as well as the structure and extent of the comet’s tail, to refine its characterization. MeerKAT’s ongoing observations and subsequent ones offer valuable insights into interstellar comet behaviors and their dynamic processes when influenced by solar radiation.
This post was last modified on 11/10/2025