The secret life of ultra-low frequency gravitational waves

The detection of ultra-low frequency gravitational waves is delivering insights into the development of the universe, according to researchers at the University of Birmingham. Gravitational waves that transverse the universe at the speed of light have many wavelengths, or frequencies.  While scientists have not detected gravitational waves at extremely low ‘nanohertz’ frequencies, that is rapidly changing.

Researchers at the NANOGrav collaboration are using pulsars to precisely time the rotation periods of a network, or array, of millisecond pulsars spread throughout our galaxy. These then can be used to measure the fractional changes caused by gravitational waves as they spread.

What is producing the signals?  University of Birmingham’s Institute for Gravitational Wave Astronomy scientists believe it will be extremely difficult to settle on an answer using only data from pulsar timing arrays (PTAs). However, in a newly published paper (18 October 2021) in Nature Astronomy, they suggest that combining this new data with observations made by other projects such as the European Space Agency’s Gaia mission, will help the different signals to be disentangled and interpreted.

So far, the main theory for ultra-low frequency gravitational waves is that they are caused by a population of the supermassive black holes at the center of merging galaxies. It has also been suggested that extremely low frequency gravitational wave signals could instead be generated shortly after the big bang by other processes if the Universe underwent what physicists refer to as a phase transition at the correct temperature.

Original Release: Eureka Alert