Hessels’ research focuses on using large radio telescopes to explore the astrophysics of some of the most energetic objects and phenomena in the Universe. Astronomical observations conducted using radio waves and radio telescopes (Radio Astronomy) play a critical role in the study of transient astrophysical phenomena (short-lived and often extremely energetic astrophysical events). Thanks to cutting-edge radio telescopes like the Low-Frequency Array (LOFAR), the field of radio astronomy has entered a new golden age in which the exploration of transient radio phenomena is a key scientific driver. Also called Time Domain Astronomy, the study of how astronomical sources change in brightness - sometimes within milliseconds or less - is a powerful way to probe some of the most extreme astrophysical situations in the Universe, and thereby test fundamental physical theories of gravity, dense matter and cosmology. Hessels’ past research highlights include the discovery of the fastest-spinning neutron star and a hyper-massive neutron star, as well as the discovery and detailed study of repeating fast radio bursts, which are enigmatic radio flashes originating from deep space.