Results of ten years of UCLA SETI searches with the Green Bank Telescope

TL;DR

Over ten years, UCLA SETI used the Green Bank Telescope to search for extraterrestrial signals, analyzing over 70,000 stars, with AI and citizen science aiding detection and classification.

Contribution

This study provides extensive observational data, improved detection methods, and stringent limits on extraterrestrial transmitter prevalence within 20,000 light-years.

Findings

Detected no extraterrestrial signals, confirming low prevalence of detectable transmitters.

Achieved 94-99% efficiency in narrowband signal detection across frequency drift rates.

Engaged over 40,000 volunteers in citizen science platform for signal classification.

Abstract

We have been conducting a search for narrowband radio signals with the L-band receiver (1.15-1.73 GHz) of the 100 m diameter Green Bank Telescope (Margot et al., 2023). So far, we have captured radio emissions from 70,000+ stars and planetary systems in the ~9 arcminute beam of the telescope. Our data-processing pipeline has a demonstrated 94%-99% efficiency for the detection of narrowband signals across the full range of frequency drift rates (+/-9 Hz/s). All 100 million candidate signals detected to date were either automatically (99.5%) or visually (0.5%) confirmed to be anthropogenic in nature. These results allow us to place stringent limits on transmitter prevalence: at the 95% confidence level, the fraction of stars within 20,000 ly that host a transmitter that is detectable in our search (EIRP > 5e16 W) is <6.3e-5. Our most interesting signals have been uploaded to a citizen science platform (http://arewealone.earth), where 40,000+ volunteers to date have contributed insights and classifications. We are using artificial intelligence (AI) to accelerate our search, automatically excise radio frequency interference, and improve signal detection. UCLA SETI research has involved ~200 undergraduate and ~20 graduate students so far.