Podcaster: Beth Johnson, Franck Marchis, and Simon Steel (alternate hosts); Guest: Dr. Nathalie Cabrol

Title: SETI Live: Pulsars Reveal Cosmic Hum

Organization: SETI Institute



Gravitational waves play a cosmic symphony as they pass through our galaxy. This week, the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) Physics Frontiers Center released the results of 15 years of data in a set of papers published in The Astrophysical Journal Letters. This research is the first evidence of gravitational waves at very low frequencies.

The team, comprised of 190 scientists, transformed our region of the Milky Way Galaxy into an immense gravitational-wave antenna using pulsars. NANOGrav’s endeavor involved collecting data from 68 pulsars, fashioning a pulsar timing array—a distinctive type of detector.

In 2020, with over a decade of data, NANOGrav scientists detected hints of an additional enigmatic “hum” in the timing behavior of all the pulsars in their array. After exploring alternative explanations, they grew confident in the authenticity of this signal. Its detection became increasingly feasible with more extensive observations. 

However, at that stage, the gravitational-wave signature predicted by general relativity remained too faint to emerge. After fifteen years of pulsar observations, the evidence of gravitational waves, with periods spanning years to decades, emerges prominently.

Join Simon Steel, Deputy Director of the Carl Sagan Center, as he discusses this groundbreaking research with NANOGrav team member and SETI Institute researcher Dr. Michael Lam.

Press release:

Bio: Beth Johnson is a communications specialist and social media manager with a degree in physics and master’s work in planetary science. She specializes in meteor showers, icy moons, and anything with volcanoes.

Franck Marchis is a senior planetary astronomer and chair of the exoplanet group at the Carl Sagan Center of the SETI Institute and Chief Scientific Officer and Founder at Unistellar. He has dedicated his work to the study of our solar system, specifically the search for asteroids with moons, using mainly ground-based telescopes equipped with adaptive optics.

Simon Steel is Deputy Director of the Carl Sagan Center for Research at the SETI Institute. As an observational astrophysicist, he specialized in optical spectrophotometry, with an interest in the star formation histories of galaxies.

Dr. Nathalie Cabrol, Director of the SETI Institute’s Carl Sagan Center

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