Imaging black hole shadows with Prof Roger Deane

Posted on July 19, 2019

Prof Roger Deane has established a new radio astronomy research group at the University of Pretoria. He completed his doctorate at the University of Oxford before returning to South Africa to work primarily on the MeerKAT and Square Kilometre Array projects. His research interests include the study of supermassive black holes, strong gravitational lensing, and the evolution of distant galaxies. In addition, he has a deep interest in radio astronomy techniques. Prof Deane was part of the team of over 200 scientists across the globe who worked to bring the first image of a black hole to life. He recently gave a public lecture at UP which made his research more accessible to a general audience. Tukkievaria had a chat with Prof Deane to find out more about his research field.


1. Tell us a bit about your contribution to the Event Horizon Telescope?

My primary role was to lead the development of a simulation of the entire Earth-sized instrument, including the subtle effects of weather above each site, imperfections in the engineering of the dishes, and other impacts on the indirect, mathematically abstract method used to make the image. This indirect method of taking a photograph of a black hole requires a complex instrument, which requires that we understand each component of it as best as we can. Our work helped with that key goal.

2. How did you feel when you first saw the image that your software simulated?

A combination of disbelief and utter amazement. To be quite honest, I thought we would take a few years more to make an image that looked far less clear than that. It was an incredible feeling that I’ll never forget.

3. How did you all manage to keep this a secret for so long?

Well we just had to, there was no choice. Extraordinary claims require extraordinary evidence. So once we had clear evidence of a ring-like structure consistent with the prediction of a black hole shadow, the work then had to step up a gear in order to demonstrate, through multiple independent algorithms, that the shadow feature was robust to any sort of human bias or preconceived expirations of what we expected to see. That a result this big did not leak for over 10 months is a remarkable testament to the international team, in my view.

4. How does an Earth-sized telescope work?

The telescope has a virtual size of Earth since the maximum distance between two individual antennas in the network is comparable to the size of the planet. The focus of this Earth-sized telescope is a virtual rather than physical one – formed by software rather than planet-sized pieces of steel. The MeerKAT and Square Kilometre Array telescopes also rely on this Nobel prize-winning technique, which is known as radio interferometry. It can be likened to trying to piece together someone’s reflection in a broken mirror with just a handful of tiny pieces of glass in place. Or like recording someone playing an out of tune piano and then manipulating the recording to make the instrument sound like it’s perfectly in tune. These algorithms come at a cost, however, requiring significant computational power to process large amounts of data.

5. What are some of the practical considerations or applications of this research?

The technique of interferometry is used in a wide variety of applications, such as synthetic aperture radar which is used for Computed Tomography (CT) scans of the brain. Improvements to one of these can often result in improvements for all. Beyond that, this research has had to pioneer methods of recording vast troves of data at very high speeds, which has obvious economic potential.

6. What is the future of radio astronomy in SA?

Extremely bright. We have had the benefit of visionary policy makers in this regard over the past 2-3 decades, culminating in South Africa winning the bid to host the largest radio telescope on Earth – the Square Kilometre Array (SKA). This will be largest scientific infrastructure on Earth and it is being built on African soil thanks so the now internationally renowned South African Radio Astronomy Observatory. En route to that, SARAO (South African Radio Astronomy Observatory) has delivered the MeerKAT telescope, which is already producing major breakthroughs, providing the best view of the radio universe ever seen – for this type of telescope.

7. What would you say to school learners or potential graduate students who are aspiring radio astronomers and want to #ChooseUP?

There has never been a better time to study astronomy in South Africa – you can work on an iconic project and develop highly sought after mathematical, physics, and computational skills that are applicable in a wide range of industries.

8. What are some of your other research interests?

Trying to find when black holes come in pairs – based on theory, we expect this happens far more frequently than our observations currently show, which is a puzzle. And what’s better for a scientist than to work on a difficult puzzle? A second major research thrust of mine is the study of what are known as gravitationally lensed galaxies. These are distant galaxies that happen to be almost exactly aligned with a more nearby [but still very distant] galaxy. Because the galaxies are so massive, they distort space-time as described by Einstein’s General Theory of Relativity. The result is like looking at an object through a droplet of water on a window pane – you see an enlarged but distorted view of it. It is also a bit like pointing our Earth-based telescope at a large cosmic telescope so we see much deeper views of the universe than would be otherwise possible.

9. What is your message to other young researchers across UP?

Your reach should exceed your grasp. Don’t underestimate yourself, go after big, challenging problems. Our country needs bold thinkers who can act on ideas to move it forward.

10. What do you do for fun?

These days there is nothing I find more relaxing that playing with my nine-month-old son, the day or week’s stressful matters on my mind seem to disappear within seconds of hanging out with him. When I had some more time on hands, I was a big fan of long-distance running and golf, but time for that seems to have thinned out in the last while.

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