NRF|SAAO Cape Town Open Night

Speaker: Dr. Prerna Rana

Title: Listening to the Universe with Pulsars

Abstract: Pulsars are rapidly spinning neutron stars that act like natural cosmic clocks, sending out regular pulses of radio waves. By carefully measuring the arrival times of these pulses with radio telescopes on Earth, scientists can detect tiny disturbances caused by passing gravitational waves – ripples in space-time first predicted by Albert Einstein. While observatories like LIGO and Virgo listen for high-frequency gravitational waves from colliding black holes or neutron stars, Pulsar Timing Arrays (PTAs) are sensitive to very low-frequency waves, with periods of years to decades. These waves are thought to come from pairs of supermassive black holes orbiting each other in the distant universe. In this talk, I will introduce what pulsars are, how we turn them into a galaxy-sized gravitational wave detector, and what International PTA collaborations will tell us about the hidden universe of giant black holes.

Bio: Dr. Prerna Rana is a postdoctoral researcher in astronomy at the University of Cape Town, supported by SARAO. She studies pulsars which are rapidly spinning neutron stars that act like cosmic clocks—and uses them to search for gravitational waves, the tiny ripples in space-time predicted by Einstein. Prerna works with International teams, including the Indian Pulsar Timing Array, the African Pulsar Timing group, and the International Pulsar Timing Array collaborations, which observe pulsars and combine data from large radio telescopes to detect nanohertz gravitational waves from supermassive black hole binaries in the Universe. Earlier, during her PhD, she studied the motion of matter around rotating black holes to better understand the extreme physics of these fascinating objects.