Jonty Marshall
Jonty Marshall
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Dr. Jonathan (Jonty) Marshall received his Ph.D. from The Open University (UK) in 2011, on the detection and analysis of dusty debris discs around main-sequence stars.
His first postdoctoral position was at the Universidad Autonoma de Madrid, Spain for four years. There he worked on data reduction and modelling for the Herschel Space Observatory's key programme ‘Dust around nearby stars’, identifying circumstellar debris around nearby, Sun-like stars through detection of excess emission at far-infrared wavelengths.
After that he moved to UNSW in Sydney, Australia where he obtained independent research funding as a Vice Chancellor’s Postdoctoral Research Fellow, working with the Exoplanetary Science group to pursue questions regarding the connection between debris discs and exoplanets within planetary systems.
Following a three year stint at UNSW, he moved to Institute of Astronomy and Astrophysics, Academia Sinica in Taipei, Taiwan, where he was appointed as an independent postdoctoral fellow, working with the Interstellar and Circumstellar Matter group; he is currently deputy group leader and has broadened his research interests into dust in the interstellar medium and in the environments of evolved stars.
Having successfully obtained external funding from the Taiwan Ministry of Science and Technology, Jonty now holds a Research Scholar position at the Institute of Astronomy and Astrophysics, Academia Sinica in Taipei, Taiwan. He continues to study planetary systems in detail, with a focus on millimetre interferometric measurements of debris disc architectures.
Research Interests
Research Interests
My primary research interest is circumstellar dust discs as evidence of planetary systems around mature, main-sequence stars.
These discs are the tenuous, dusty remnants of the gas-rich, primordial protoplanetary discs that surround stars during their formation, the birthplace of planetary systems like our own. They are composed of rocky and icy bodies ranging from micron-sized dust grains to kilometre-sized planetesimals (asteroids and comets). The dust grains are the remnants of collisions between larger bodies in the disc; these systems are therefore known as debris discs.
We most commonly observe debris discs as excesses above their host stars photospheric emission at infrared wavelengths, produced by thermal emission from dust grains, but have also observed them at optical and near-infrared wavelengths by the light they scatter from their host star. We have identified around 20 +/- 2 % of nearby, Sun-like stars with excess consistent with the presence of cool debris analogous to the Edgeworth-Kuiper belt.
Through hierarchical growth, dust grains present in a primordial protoplanetary disc stick together in collisions, becoming pebbles, boulders, and eventually planetesimals. It is these planetesimals that constitute the building blocks of planets. We might therefore surmise that the presence (and properties) of dusty debris and planets around another star should be correlated. Indeed, we find a higher incidence of planets around systems with debris and have further identified an anti-correlation between planet mass and debris disc brightness.
As an easily visible remnant of the planet formation process, a debris disc is therefore an ideal marker of a planetary system existing around another star. For sun-like stars, these planetary systems represent alternative outcomes of the same planet formation process that produced our own solar system with its two debris belts (the Asteroid belt and Edgeworth-Kuiper belt) and eight planets. By studying such systems in detail we thus obtain an understanding of the formation timescales, range of outcomes, and incidence of planetary systems like our own.
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