Building big telescopes to unravel the structure of the Universe
Professor Melanie Johnston-Hollitt studies cosmic magnetism and galaxy clusters, the largest gravitationally-bound structures in the Universe. But to do this, she is also involved in developing and building the scientific instruments needed to study the Universe in such detail.
About Professor Melanie Johnston-Hollitt
Melanie always intended to be an astrophysicist, but after starting out cleaning photomultiplier tubes to study cosmic rays at the Woomera Rocket Range, and then trying optical astronomy at the Anglo-Australian Telescope at Siding Springs Observatory, she settled on radio astronomy. She has since worked on the design and construction of several major international radio telescopes and is currently Director of the Murchison Widefield Array (MWA), the first operational pathfinder telescope for the Square Kilometre Array (SKA).
What drew her to science?
“It sounds like a terrible cliché,” Melanie admits, “but it started when I was about two, and my grandmother used to take me outside and show me the night sky, and tell me about the stars and the planets. I really loved it, so when my father suggested that I should follow that interest and become an astronomer, that’s what I decided to do. I was an extraordinarily stubborn kid, and I held onto that idea right through school, aiming to eventually do a PhD in astrophysics.”
Research with supercomputers
Melanie has been constrained by computation her entire career. She explains: “During my PhD, I’d make observations at the telescope, but then have to go to CSIRO to process the data, as their computer cluster was bigger than anything we had at the university at the time.”
“Eventually computing became more powerful, and there was a period about 10 years ago when you could produce and reduce astronomical data on your laptop. But now we’ve gone through a renaissance with radio astronomy, we’ve built a collection of new telescopes which produce absolutely prodigious amounts of data. Modern supercomputers are now absolutely necessary again to store, process and analyse it all.”
The way of working is basically the same as it was before, but the scale improvements are literally astronomical. Putting it in perspective, Melanie reflects: “For my PhD it took me three years to collect my data and I ended up with just nine data points to draw my conclusions from. My students can now get that amount of data and that result in a day, just because the telescopes have got much better, and the processing has got so much faster. We’re getting closer to the answers than we’ve ever been able to before.”
While Melanie is trying to understand the history of how magnetism arose in the Universe, and how magnetism affects astronomical processes today, particularly in galaxy clusters, much of her research is working out how to scale up processing the data from these modern telescopes. Algorithm development and optimisation are critical to make the most effective use of modern instruments and make next-generation telescopes like the SKA possible.
It’s at the intersection of astronomy, physics, computing and mathematics that down-to-Earth applications occur.
“We’re driven by curiosity, and curious about things that are really hard to understand, like galaxy evolution. But in the process of trying to answer our questions, we develop technology that is useful in so many other ways too. People who want to understand the physics of the Universe have come up with algorithms that led to our current Wi-Fi standards. Interferometry, the fundamental technique that modern radio astronomy is based on, is now used in medical imaging, and has been revolutionising diagnostic medicine and human healthcare in just the last 10–20 years. And through studying our ionosphere and working out how it distorts the radio signals we’re trying to measure, radio astronomers have enabled accurate transmissions of signals from satellites to the ground, which underpins our Global Positioning Systems (GPS).”