Colloquium Schedule

Fall 2023

Detecting Gravitational Waves with Pulsar Timing Arrays

Tristan Smith, Swarthmore College
Friday, September 22 at 12:45

Gravitational wave astronomy became a reality in 2015 with the first detection of gravitational waves from a pair of black holes that had smashed into each other. This milestone (and the hundreds of events detected since then) have all been measured using 4km-long interferometers sitting on the earth’s surface. These instruments are sensitive to gravitational waves with frequencies around 100 cycles per second, which limits the type of black holes they can detect. Pulsar timing arrays constitute a galaxy-sized gravitational wave detector which can potentially probe frequencies as low as one cycle every 10 years, giving us access to black holes with masses as much as one billion times that of the sun. On 29 June 2023, the NANOGrav Collaboration, the European Pulsar Timing Array, the Parkes Pulsar Timing Array, and the Chinese Pulsar Timing Array, all announced the detection of gravitational waves (that earth-based detectors had not sensed). I will discuss how pulsar timing arrays fit into gravitational wave astronomy, point out some curious aspects of these first detections, and describe what we hope to learn about the universe with this new and extraordinary tool.