Nanohertz gravitational waves from pulsar timing arrays

Pulsar timing arrays (PTAs) use observations of millisecond pulsars to detect nanohertz gravitational waves. In June 2023, 4 PTAs presented the results of such searches in their datasets and found compelling evidence for the spatial correlations characteristic of the gravitational wave background. I will introduce how we search pulsar timing array data for gravitational wave signals and summarise the results of recent searched of the European PTA data.