Since the first direct detection of gravitational waves by the Laser Interferometer Gravitational-Wave Observatory (LIGO) in 2015, a new method of gravitational-wave detection has emerged: pulsar timing arrays (PTAs). They can probe gravitational waves with frequencies about 11 orders of magnitude lower than LIGO by monitoring millisecond pulsars over decades, thus providing complementary information about the gravitational-wave universe. These pulsars act as extremely precise cosmic clocks and a passing gravitational wave leaves an imprint on the predictable times-of-arrival of their radio pulses. PTA collaborations around the globe recently found evidence for a so-called stochastic gravitational-wave background at these low frequencies, which marks the start of nanohertz gravitational-wave astronomy, promising many exciting discoveries in the next decades.
Bence Bécsy’s research focuses on detecting and characterizing these low-frequency gravitational waves with novel data analysis techniques. This ultimately helps us understand the astrophysical sources emitting these gravitational waves. These are most likely pairs of the largest black holes in the universe, so-called supermassive black hole binaries. There are many open questions around the formation and evolution of these black holes, which we hope to answer with PTA observations. However, it is also possible that some of these low-frequency gravitational waves are coming from the early universe, which could shed light on new physics beyond the Standard Model.