Dr Giovanna Zanardo
PhD Candidate Giovanna Zanardo used to engineer bridges, now she studies the massive remnants of exploding stars. She applies her knowledge of Earthly structures and how they react to dynamic forces to the study of supernovae, figuring out what’s going on inside something a bit more ‘out of this world!’ Along the way she also gets to check out the inner workings of radio telescopes, and have a front row seat to the development of the SKA.
The interview below was conducted in 2013, Dr Zanardo has since graduated from our PhD program.
What are you working on now?
My PhD revolves around the remnant of Supernova (SN) 1987A, a massive star that exploded in February 1987. The remnant is located in the Large Magellanic Cloud, so it’s visible only in the southern skies. My research is based on observations with a number of telescopes. I’ve been using the Australia Telescope Compact Array (ATCA), a 6-dish interferometer in NSW, and the Australian Long Baseline Array (LBA), which connects radio telescopes in Australia and New Zealand via Very Long Baseline Interferometry (VLBI). More recently we have been awarded observing time with the Atacama Large sub-Millimetre Array in Chile. At the moment I’m going through the most recent data obtained with these telescopes, since we have ongoing observing programs on each of them. As we speak, I’m also using the Parkes telescope, as a single dish, to search for a pulsar inside the supernova remnant.
What got you into astronomy?
I always loved physics and astronomy, but I’ve become a structural engineer because I also love structures. In engineering I’ve specialized in the analysis of the response of spatially developed structures, such as bridges or tunnels, to dynamic forces, such as vehicle-induced actions, blasts and earthquakes. When I arrived in Western Australia to work at an engineering project, I’ve learned about the upcoming Square Kilometre Array and I thought it was the time to get into radio astronomy!
I contacted Lister Staveley-Smith and we had a long chat about structures. Then Lister showed me some radio images of the remnant of Supernova 1987A, and explained how the effects of this massive explosion in space have been continuously monitored with the ATCA. The idea of studying the dynamic evolution of this fascinating object sounded like the most interesting project I could be involved with, while I was very keen to learn the workings of complex instruments such as radio telescopes.
Why is your work important for ICRAR?
The remnant of Supernova 1987A, as the only nearby core-collapse supernova observed to date, is providing a unique insight into how massive stars explode and what is left behind. In the case of SN 1987A, it’s the first time that we can observe in ‘real’ time and with unprecedented detail the interaction of the shock wave, which propagates at some 35,000 km/s, with the circumstellar medium, i.e. the material left by the exploded progenitor. Radio observations of the evolving remnant allow testing theoretical models of particle acceleration mechanisms and cosmic ray production. Research on SN 1987A falls under the ICRAR key research area on time-domain astronomy, i.e. on fast-evolving objects, which change every time we point a telescope at them. This supernova remnant also provides a great opportunity to test instruments and techniques to capture high-resolution images of the morphology of the radio emission. High-resolution observations have been performed at lower frequencies via VLBI with the LBA, and at high frequencies with the ATCA.
Why did you join ICRAR?
I joined ICRAR from the beginning in 2009 to work with Lister Staveley-Smith. ICRAR is strongly linked to the upcoming Square Kilometre Array, and it is fantastic to be in a place where you can follow the project of such a gigantic telescope from its inception.
Where were you before you came to work for ICRAR?
I was in Western Australia as an engineer working on bridge structures across the State. Before that I was in the UK working on some very interesting projects of structural dynamics and earthquake engineering.
What’s your favourite part of your work?
I find supernovae and supernova remnants really fascinating, but I particularly like the observational side of my project, and the instrumental or engineering component attached to it.
What do you think is the most exciting thing about astronomy today?
I think that radio astronomy is the most interesting field to work in at the moment, especially because of the massive telescopes that are under construction and the number of discoveries that will be made with them.
Your work recently gathered attention because you took the highest resolution image of Supernova 1987A, what sparked you to create that image and what did it tell us?
This new data provide an image of the supernova remnant with the highest resolution at high radio frequencies. The higher the frequency, i.e the smaller the wavelength, more details are visible in the remnant structure at the shock front, where the blast wave collides with the material left by the progenitor star. As a result of this collision, particles are trapped by the shock front and are accelerated to very high energy levels. It’s like having a real-life particle accelerator in space, where we can zoom-in and study how the particle acceleration process works.
The high-resolution of these radio images has also allowed a detailed comparison with the optical images obtained with the Hubble Space Telescope and with the X-ray images obtained with the Chandra Observatory, so to improve our understanding of the progenitor’s explosion. On the other hand, the emission from the centre of the remnant that is visible in this image, points to a young neutron star sitting under the debris left from the progenitor.