EPISODE THREE
Australian highlight: Professor Naomi McClure-Griffiths, radio astronomer
Ah! moment: Discovering an arm of the Milky Way (2004)
Professor Naomi McClure-Griffiths is famous on a galactic scale.
She is an Australian Research Council Laureate Fellow and the Associate Director (Research) at ANU’s Research School of Astronomy & Astrophysics.
Always fascinated by maths and science, she studied physics in Ohio in the USA, and completed a PhD in Astrophysics in Minnesota, for which she received the award for best dissertation. But it was a discovery made with Murriyang, CSIRO’s Parkes radio telescope, three years later, which led to international recognition and a Prime Minister’s prize in 2006. At only 30 years old, she was described as “one of the strongest leaders in astronomy of her generation in the world”.
Image: Naomi McClure-Griffiths. Credit: ANU
Header image: The Milky Way Galaxy's hydrogen gas. Credit: Naomi McClure-Griffiths
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Armfuls of galactic gas
"Surely somebody else has found this?"
was all Naomi could think as she looked at the data in front of her, collected with the radio telescope at Parkes, New South Wales. She’d detected something remarkably large – a whole band of interstellar gas across our sky.
Possible explanations were thinning out, but there was one which continued to fit the models Naomi made and the literature she’d read…
Just like that, in her 20s, Naomi had discovered a spiral arm of our Milky Way.
Image: Pinwheel Galaxy (M101). Credit: ESA/Hubble
Radio eyes on the galaxy
It wasn’t known that the Milky Way was a galaxy until 1923. General consensus was that the Milky Way was an ‘island Universe’ where all the nebulae, stars and planets resided, with nothing beyond. To test this, Edwin Hubble measured the characteristics of a flashing star in the Andromeda Galaxy and applied Henrietta Swan Leavitt’s models and methods for measuring distances. In doing so, he proved that Andromeda was beyond the edge of the Milky Way.
[As a sidenote, Henrietta Swan Leavitt’s work in the 1900s and 1910s was exceptional: she discovered the relationship between a flashing star’s (now called a Cepheid variable) timings and its brightness, and realised this could be used to measure distances in space. By knowing the timing, you know how bright it should be – the dimmer the star, the further away it is.]
So, the Milky Way was a galaxy, with a thick central band of stars, but the exact structure is largely a mystery, as Naomi says,
“It’s like trying to figure out where the shops are in your neighbourhood, but you can’t leave your house.”
Understanding the structure of other galaxies is much easier, as we can see them in their entirety. Think the beautiful Pinwheel galaxy (above), captured by the Hubble Space Telescope (mostly an optical telescope) or the Whirlpool Galaxy (below), as seen by the James Webb Space Telescope (mostly an infrared telescope). Sometimes, even from our viewpoint, another galaxy’s structure may be hidden from us. Take the Sombrero Galaxy (below), it is one of my favourite images of another galaxy. But at this angle, just seeing the sharp ridge, we can’t be sure of its structure.
Images:
Whirlpool Galaxy (M51). Credit: ESA/Webb, NASA & CSA, A. Adamo (Stockholm University) and the FEAST JWST team
Sombrero Galaxy (M104). Credit: NASA/ESA and The Hubble Heritage Team (STScI/AURA)
Optical telescopes had only taken us so far to understand the shape of the Milky Way, mapping the distances to fields of stars and globular clusters. From the 1950s, the invention of radio astronomy plus the discovery of a way to see hydrogen gas – the most abundant element in the Universe – and map the gas’ distribution, enabled a classification of the Milky Way as a large spiral galaxy.
As a radio astronomer, Naomi’s instrument of choice is a radio telescope. For this discovery, she was using Murriyang, the Parkes radio telescope, owned and operated by CSIRO, Australia’s national science agency. CSIRO is one of the first organisations in the world to do radio astronomy research, and is still a leader in the field.
Like any branch of astronomy, radio astronomy uses telescopes to capture light coming from objects in space – stars, galaxies and the gas in between. The term ‘radio’ refers to a specific energy of light, not sound. The devices which play music, or are used for communication – radios – are named for the light waves they use to transmit the signal.
Radio waves are extremely low-energy. To capture this faint energy from space, we use big dish-like telescopes, such as Murriyang, or lots of small dishes working as one like CSIRO’s ASKAP radio telescope – two instruments Naomi uses in her research. These telescopes collect the radio waves which are converted to data for supercomputers to crunch through and astronomers to observe.
Image: Murriyang, CSIRO's 64m Parkes radio telescope. Credit: CSIRO
A discovery of doubts
In 2004, Naomi was mapping the galaxy’s hydrogen gas using the new technology- and data-collecting capabilities of the Murriyang telescope. As she built images from the data, a band of hydrogen gas on the other side of the Southern Cross revealed itself.
Naomi concedes there was no immediate “Ah!” moment.
When it was looking like the fuzzy patterns on her screen were a galactic spiral arm, she doubted that such a physically large object had not been detected before. But, she had collected thousands of hours of data, and the technology had improved since previous studies: topographical-type maps were now fly-through movies, enabling a level of visualisation that hadn’t existed before.
Naomi’s sense of doubt meant checking and rechecking the work before finally writing and submitting a paper, which was published to wide-spread acclaim.
But it wasn’t until “a few years later, [when] another team found molecular gas in the same area which confirmed the discovery. By that point it was like, aha, right, got it.”
Images:
The Hubble Space Telescope in orbit. Credit: NASA.
CSIRO's ASKAP radio telescope. Credit: CSIRO.
Leading new fields of research
These days, Naomi focuses on her passion, mentoring students to do the best work they possibly can.
“Our job as supervisors is to create a project with that student that will really give a new understanding.”
She speaks with warmth and excitement about the people she explores the Universe with every day. And it is evident that they admire her too, with her empathy, intelligence and attractive research. Literally, attractive: Naomi is leading the charge on studies in galactic magnetic fields.
Magnetic fields could be as important as gravitational fields in forming galaxies and galaxy clusters, but they remain largely a mystery. It is the new frontier of radio astronomy research, with Naomi and her colleagues at the helm. The latest radio telescopes promise a new, magnetic view of the Universe.
“There’s a lot to discover in Space.”
Naomi knows there are decades of work in front of her and her talented proteges to unlock the mysteries of galactic formation. But, inspired by her work and generous mentoring, perhaps these intergalactic discoveries are closer than ever for this next generation of astrophysicists.
Image: Naomi at the time she made her discovery in 2004.
This episode's comedic guest: Jeeves Verma
Jeeves is a Sydney comedian, specialising in professional scripted and improvised comedy, built across nearly a decade of experience. Jeeves performs a new live show every year (which is madness) at the Sydney Comedy and Melbourne International Comedy Festivals; he's a faculty member at Improv Theatre Sydney; and hosts weekly trivia events. He could also host your wedding!
Fun fact, Jeeves studied Medicine once upon a time and chose to leave his medical career in pursuit of the "best medicine". Timeout described his trivia hosting as "taking you, and your most-hidden brain corners, for a whirlwind of a spin".