2/01/2021 Peter Durantine

Catching a Gravitational Wave

An alumnus, working with a Franklin & Marshall College astronomy professor as part of a larger research consortium, has co-authored a gravitational wave research paper that is expected to open a “new window” to understanding the universe.

Like lighthouses, pulsars – small, dense stars that rapidly rotate – beam signals across our galaxy and are observed by large radio telescopes on Earth as radio pulses. These extremely regular pulses can be used as precise clock-ticks to detect small timing changes arising from the presence of slowly undulating gravitational waves. 

The most recent analysis of pulsar timing data, collected by the consortium over a number of years, suggests a hint of a gravitational wave, according to the paper whose lead researcher is astrophysicist Joe Simon ’07 of the University of Colorado.

The recent report, whose co-authors also include F&M Professor of Astronomy Fronefield Crawford and about 50 other researchers, is the culmination of 13 years of work – the time that has passed since Simon graduated from F&M – of gathering and analyzing pulsar data.

“It is incredibly exciting to see such a strong signal emerge from the data,” Simon said. “Because the gravitational-wave signal we are searching for spans the entire duration of our observations, we need to carefully understand our noise.” 

The F&M alumnus led a Jan. 11 press conference at the American Astronomical Society annual meeting on behalf of the North American Nanohertz Observatory for Gravitational Waves (NANOGrav). Simon discussed the paper’s findings and said that more data is required to confirm the signal as a wave. 

  • Astronomy Professor Crawford with former F&M Astrophysicist Lommen in the early years of NANOGRAV. Astronomy Professor Crawford with former F&M Astrophysicist Lommen in the early years of NANOGRAV. Image Credit: Eric Forberger

“This leaves us in a very interesting place, where we can strongly rule out some known noise sources, but we cannot yet say whether the signal is indeed from gravitational waves,” he said.

Simon and Crawford belong to NANOGrav (as does former F&M Astrophysicist Andrea Lommen), a large scientific consortium tasked with using radio telescopes to collect data that may contain the effects of gravitational waves, which are formed by distant collisions of cosmic colossuses, like black holes, that send ripples through spacetime.

“There may be a gravitational wave signal buried in this data set, and the longer one observes and monitors this select group of pulsars, the more likely it is that such a signal will finally reveal itself,” Crawford said. 

“This particular paper finds a hint of a signal, which might be real, but it is not yet clear enough to claim a detection,” he said. “It’s just the emergence of something that is very interesting. As more data continue to be collected and analyzed, a claim of a detection might be possible soon.”

Crawford said detecting gravitational waves, and this recent finding in particular, can help answer questions about “how very distant, very massive black holes in the centers of galaxies form, interact and evolve.” 

“This work is opening a whole new window to understanding the universe through the study of gravitational waves,” he said. “For centuries, measuring light from distant objects has been the way we have sought to understand how the universe works. Now this is changing – it’s a very exciting time to be working in astronomy!”

The paper describing this work was recently published in the Astrophysical Journal Letters (Z. Arzoumanian et al., “The NANOGrav 12.5-year Data Set: Search for an Isotropic Stochastic Gravitational-Wave Background,” Astrophysical Journal Letters, 905, L34, 2020) Link: https://iopscience.iop.org/article/10.3847/2041-8213/abd401 
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