In the laboratories of the SETI Institute (Search for Extraterrestrial Intelligence), work is in full swing: astronomers have learned to detect barely perceptible fluctuations in radio signals coming from distant pulsars. These cosmic beacons, the spinning remnants of exploded stars, have long been the gold standard for scientists, but it turns out that even they are not immune to the whims of interstellar space. Gas clouds between stars can shift the arrival time of a signal by mere billionths of a second. For the human ear, that’s nothing, but for science, it’s a substantial gap.
Such microscopic delays pose a real challenge for those trying to detect gravitational waves or search for signs of intelligent life beyond Earth. If the effect of interstellar gas is not taken into account, background noise can be mistaken for a sensational discovery — or, conversely, an important signal might be missed. That’s the main intrigue fueling SETI’s latest research.
Pulsars under the microscope
Since late February 2023, the team led by Brown has been observing the pulsar PSR J0332+5434 almost daily using the Allen Telescope Array in California. This object is not just another point in the sky — it’s the brightest pulsar accessible to their equipment, located more than 3,000 light-years from Earth. Over ten months, scientists conducted nearly 400 observations, tracking minute variations in the radio signal’s ‘flicker pattern,’ a phenomenon known as scintillation.
When the radio waves emitted from a pulsar’s poles pass through clouds of ionized gas, they encounter chaotically moving electrons. These particles bend and scatter the signal, causing it to be delayed. As a result, bright and dim areas form at different frequencies, constantly shifting as the Earth, the pulsar, and the interstellar gas move. Researchers observed exactly these changes, noting that the delays could reach dozens of nanoseconds.
Gravitational waves and cosmic traps
At first glance, such deviations may seem insignificant. However, for projects searching for low-frequency gravitational waves, they are critical. These waves cause simultaneous disruptions in the arrival times of signals from various pulsars, and without correcting for the effects of interstellar gas, a genuine signal could be mistaken for a false one. An error of just a few nanoseconds can nullify months of work and lead to incorrect conclusions.
Moreover, these same effects complicate the search for extraterrestrial civilizations. Radio signals coming from deep space must display certain scintillation characteristics. If a signal fails to ‘flicker’ as expected after traveling through the interstellar medium, it is most likely of terrestrial origin. This allows scientists to distinguish real cosmic messages from interferences caused by human activity.
The fine line between noise and discovery
During a large-scale SETI campaign, researchers monitored not just a single pulsar, but twenty at once to identify patterns in scintillation changes. Although they did not observe clearly repeating patterns, scientists are confident that longer-term observations will allow for more accurate prediction and compensation of distortions caused by interstellar gas. This, in turn, will improve the chances of detecting both gravitational waves and signals from other civilizations.
Interestingly, even minor irregularities in the arrival time of pulses may hold the key to solving the universe’s most ambitious mysteries. In this context, SETI’s work gains particular value: it not only refines search techniques, but also helps us understand just how complex and unpredictable the fabric of space truly is.
The future of observations
The study’s authors emphasize that achieving maximum accuracy requires long-term and regular observations. Only this approach can account for all variables influencing radio signal propagation. The next phases of research are already planned — scientists intend to extend the observation timeline and add new targets, aiming to build the most comprehensive picture possible of how the interstellar environment affects pulsar signals.
In the coming years, research of this kind could prove decisive in the search for gravitational waves and extraterrestrial civilizations. After all, every nanosecond glitch is more than just a technical hiccup — it’s a potential clue leading to new discoveries.
RUSSPAIN reminds readers that the SETI Institute is one of the world’s leading organizations dedicated to searching for signals from extraterrestrial civilizations and studying the nature of cosmic radio signals. Founded in the United States, the institute brings together astronomers, engineers, and data analysis experts to develop unique methods for analyzing and interpreting information received from the farthest corners of the universe. Thanks to their work, humanity moves closer to solving one of the greatest mysteries: is there life beyond Earth?
