UMD Astronomer Helps Find First Evidence of Constant, Low-Frequency Gravitational Waves

Scientists using large radio telescopes to observe rapidly rotating stars called pulsars have found the first evidence of gravitational waves at extremely low frequencies, according to a set of five papers published this week in The Astrophysical Journal Letters. The discoveries could help researchers unlock the secrets of gravity and its effect on the cosmos.

The papers are the culmination of 15 years of data acquired by the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) Physics Frontiers Center, a collaboration of more than 190 scientists that includes Elizabeth Ferrara, an associate research scientist in UMD’s Department of Astronomy.

Ferrara, who is also a NASA research scientist, said that scientists are using pulsars—the ultra-dense cores of exploded stars—to study black holes and other facets of the universe.

“We’re beginning to peer deeper into how gravity has shaped the universe—to see how the most massive black holes have influenced the galaxies we see today,” Ferrara said.

While earlier results from NANOGrav uncovered an enigmatic timing signal common to all the pulsars observed, the signal was too faint to reveal its origin. The full scope of the data demonstrated that the signal is consistent with slowly undulating gravitational waves passing through our galaxy.

In 2016, the Laser Interferometer Gravitational-wave Observatory became the first experiment to directly detect gravitational waves. However, the newly discovered waves could only be spotted with a detector much larger than Earth.

To create one, astronomers turned a section of the Milky Way into a huge gravitational-wave antenna by using pulsars to create a “pulsar timing array”—a detector that’s co-managed by the partners in Australia, China, across Europe and in India.

Ferrara played a key role in expanding the number of pulsars observed by NANOGrav to 68, enabling scientists to log thousands of hours of observations and improve their odds of finding gravitational waves.

This article was adapted from a news release by NANOGrav.