New SETI Study: Why We Might Have Been Missing Alien Signals

Source: Slashdot

Overview

After decades of searching for extraterrestrial intelligence, the nonprofit SETI Foundation announced a new study by researchers at the SETI Institute suggesting that stellar “space weather” could make radio signals from extraterrestrial intelligence harder to detect.

Stellar activity and plasma turbulence near a transmitting planet can broaden an otherwise ultra‑narrow signal, spreading its power across more frequencies and making it more difficult to detect in traditional narrowband searches. For years, many SETI experiments have focused on identifying spikes in frequency—signals unlikely to be produced by natural astrophysical processes.

The new research highlights an overlooked complication: even if an extraterrestrial transmitter produces a perfectly narrow signal, it may not remain narrow by the time it leaves its home system.

“If a signal gets broadened by its own star’s environment, it can slip below our detection thresholds, even if it’s there, potentially helping explain some of the radio silence we’ve seen in technosignature searches,” said Dr. Vishal Gajjar, astronomer at the SETI Institute and lead author of the paper.

The researchers created a practical framework for estimating how much broadening could occur for different types of stars—and accounting for space weather—by using radio transmissions from spacecraft in our own solar system and extrapolating to other stellar environments.

Implications for Future Searches

The study’s co‑author, a SETI Institute research assistant, suggests this could lead to better‑targeted SETI searches. M‑dwarf stars—about 75 % of stars in the Milky Way—appear to have the highest likelihood that narrowband signals would be broadened before leaving their system.