Daniel is a senior postdoctoral researcher in Swinburne’s Centre for Astrophysics and Supercomputing (CAS), working as part of the ARC Centre of Excellence for Gravitaitonal Wave Discovery (OzGrav). His primary research interest is the precision timing of pulsars to understand extreme and fundamental physics. Daniel observes pulsars using some of the best radio telescopes in the world, to explore the properties of neutron star matter and search for gravitational waves (GWs). Daniel is a leader of the Parkes Pulsar Timing Array (PPTA) collaboration, which is the longest-running pulsar timing array project in the world. The PPTA uses Murriyang, CSIRO’s 64-m radio telescope in Parkes, to regularly observe millisecond pulsars. The goal is to use these pulsars to detect and study ultra-low-frequency GWs emitted by supermassive black hole binary systems. Daniel currently serves as chair of the International Pulsar Timing Array (IPTA) Steering Committee and is a foundational member of the MeerKAT Pulsar Timing Array (MPTA), which is also searching for GWs using the MeerKAT radio telescope in South Africa. In his spare time Daniel trains for ultra endurance races including Ironman triathlons and trail ultramarathons. In 2022 he qualified for, and competed in, the Ironman world championship in Kona, Hawaii.
Neutron stars are some of the most extreme objects in the universe. Formed from the collapsed cores of supergiant stars, they weigh more than our Sun and yet are compressed into a sphere the size of a city. The dense cores of these exotic
stars contain matter squashed into unique states that we can't possibly replicate and study on Earth. That's why NASA is on a mission to study neutron stars and learn about the physics that governs the matter inside them. My colleagues and I
have been helping them out. We used radio signals from a fast-spinning neutron star to measure its mass. This enabled scientists working with NASA data to measure the star's radius, which in turn gave us the most precise information yet about
the strange matter inside.
When black holes and other enormously massive, dense objects whirl around one another, they send out ripples in space and time called gravitational waves. These waves are one of the few ways we have to study the enigmatic cosmic giants that create them. Astronomers have observed the high-frequency “chirps” of colliding black holes, but the ultra-low-frequency rumble of supermassive black holes orbiting one another has proven harder to detect. For decades, we have been observing pulsars, a type of star that pulses like a lighthouse, in search of the faint rippling of these waves. In June 2023, pulsar research collaborations around the world – including ours, the Parkes Pulsar Timing Array – announced their strongest evidence yet for the existence of these waves.
One enigmatic feature of the interstellar plasma is the presence of dense, compact, and intensely-turbulent regions, akin to an interstellar tornado. These so-called extreme scattering events, or ESEs, are poorly understood because they are difficult to study. Our current understanding is so poor that scientists would expect such extreme objects to quickly destroy themselves. How they form and how they sustain themselves is a mystery. The solution to this puzzle likely involves the magnetic fields in our Galaxy but further study of ESEs is critical. Unfortunately, ESEs are so small by astronomical standards, that they are completely invisible to other areas of astronomy.
Pulsars—rapidly-spinning remnants of stars that flash like a lighthouse—occasionally show extreme variations in brightness. Scientists predict that these short bursts of brightness happen because dense regions of interstellar plasma (the hot gas between stars) scatter the radio waves emitted by the pulsar.