Researchers at the SETI Institute have made significant advancements in understanding how interstellar space affects the transmission of radio signals, a discovery that can enhance the search for extraterrestrial life. By analyzing the “twinkle” of pulsars, scientists are refining their cosmic clocks, which play a crucial role in detecting low-frequency gravitational waves and identifying potential signals from intelligent life beyond our planet.
The study, led by Grayce Brown of the SETI Institute, reveals that the gas found between stars can cause pulsar signals to be delayed by billionths of a second. While these timing shifts are imperceptible to humans, they are critical for astronomers relying on pulsars as ultra-precise timekeepers. “Pulsars are wonderful tools that can teach us much about the universe and our own stellar neighborhood,” Brown stated.
Beginning in late February 2023, Brown and her team conducted an extensive observing campaign using the Allen Telescope Array in California. Over a period of ten months, they monitored the pulsar PSR J0332+5434, a rapidly spinning remnant of a neutron star located more than 3,000 light-years from Earth. This pulsar is notable for being the brightest one visible to the telescope.
The research involved nearly 400 observations, enabling the team to detect variations in the pulsar’s scintillation pattern—its “twinkling” caused by the passage of radio waves through clouds of charged gas. This scintillation is akin to how stars appear to twinkle when viewed from the Earth’s atmosphere. As the pulsar, the Earth, and interstellar gas move in relation to each other, the radio signals experience fluctuations that can introduce timing delays on the order of tens of nanoseconds.
Understanding these delays is essential for pulsar timing arrays, which aim to identify low-frequency gravitational waves. If the effects of interstellar gas are not properly accounted for, they risk obscuring the faint signals that researchers are attempting to detect.
The findings also offer a new advantage for SETI researchers. By recognizing the expected scintillation patterns from pulsars, scientists can better distinguish between authentic cosmic signals and human-made interference. “We need some way to differentiate between signals coming from Earth and signals coming from beyond our Solar System,” Brown explained. If a signal lacks the anticipated scintillation, it is likely interference from terrestrial sources.
The observations were part of a larger initiative to monitor approximately 20 pulsars over a year, following a pilot phase that began in late 2022. Although the team did not find a consistent pattern in the scintillation changes, they suggest that extended observing campaigns could refine predictions and improve corrections for interstellar distortion.
This research was published on December 10, 2025, in The Astrophysical Journal, marking a notable contribution to the fields of pulsar science and the ongoing quest to uncover signs of life beyond Earth.
