15 mins read 03 May 2023

All Roads Lead to an Australian Eclipse

The Western Australian coastal town of Exmouth recently experienced a rare, and exciting hybrid total solar eclipse - where the Moon passed directly over the Sun’s disc - an event that attracted 20,000 people. We spoke with three Australians who travelled in to join part of the experience, including conducting scientific observations with some of our world-class radio astronomy instruments.

The moment of totality at Exmouth. The hybrid total solar eclipse of 2023. Several prominences and a coronal loop is visible. Captured by Juergen Kaczerowski (supplied).

As the brilliant Sun rained its heat and light down on Exmouth, Melanye Wawrik looked up, through her special safety glasses towards it. The town of Exmouth was a buzz - energised by the excitement of the non-local visitors that had descended upon it, inflating its population from the usual 3,000 up to 20,000. Accommodation bookings were sold out months in advance, with one single small shed on AirBnB going for a cost of over $7,000 for the four days surrounding April 20. Someone probably paid it.  

All around, and throughout the morning, people were looking up in anticipation. The skies could not be more perfect, as the Sun slowly climbed higher in its morning arc towards the zenith. The feeling of nervousness and exhilaration grew stronger in the hundreds of people who were setting up their cameras and telescopes, testing their filters and getting ready to be some of the few people on Earth about to catch a total solar eclipse. Some came with a simple digital camera and tripod. Others, equipment valued in the thousands, specifically designed to capture these types of astronomical events. 

Melanye’s day job is a Coordinator for the Quantum Girls Project - a women in STEM and entrepreneurship project that is designed to the skills shortage and gender imbalance in STEM-related fields, that is hosted at the University of Western Australia. She, along with a friend and child, set out from their home suburb of Mount Helena, driving along in a hybrid electric vehicle, and camping along the 1,122-kilometre distance to Exmouth. There was no way that Melanye was going to miss this opportunity, given she had never seen a total solar eclipse before, and has vague memories of an annular solar eclipse when she was five (though, it was not that great). 

“What I am expecting and excited to see is the darkness when the Moon blocks out the Sun,” she said. “To actually see what it feels like to be in the shadow of the Moon, and imagine what that looks like”.

Out at sea on a large cruise ship, Professor Jonti Horner, from the University of Queensland was preparing to have his first eclipse totality experience, whilst describing the celestial dance in the heavens above to fellow passengers. As an astronomer and astrobiologist, Prof. Horner has looked for the telltale signature of exoplanets crossing in front of their host stars using telescopes based out in Toowoomba, but this was to be his first ever chance to see the full effect of the light of our star disappearing behind the lunar disc. 

Living in Toowoomba in Queensland, Prof. Horner did chase the 2012 solar eclipse in Cairns, but unfortunately, it was clouded out at just the right time. This time around, he took his parents and flew to Perth, then Fremantle, before joining an ocean liner full of eclipse enthusiasts to travel up the West Australian coast. 

“I’m really looking forward to experiencing totality,” he said. “Seeing the sky darken, the stars and planets come out - simply a chance to see it, and share this experience with my family.” 

Core region of the ASKAP telescope, located at Inyarrimanha Ilgari Bundara, the CSIRO Murchison Radio-astronomy Observatory. ASKAP performed science operations during the 2023 Exmouth eclipse. Credit: CSIRO.

Meanwhile, Dr Vanessa Moss - a radio astronomer from Australia’s national science agency, CSIRO was in Perth, waiting for the partial eclipse to reach its maximum. From here, 70% of the solar disc would disappear behind the Sun. Dr Moss was not only there to witness the event, but as the Head of ASKAP Science Operations, she was also there to use the instrument  - which features 36 radio dish antennas  - to conduct science. 

“[Eclipses] are a chance for people to be reminded of the wonders of the Universe,” she said. “It’s a way for everyone to have access to a free spectacle that makes people ask questions about why these celestial events occur.”

“In Perth, we’re going to experience 70% partial eclipse, so I am looking forward to a pretty decent eclipse! I’m also looking forward to seeing how ASKAP goes, tracking near the Sun - a feat that we have never tested before, due to the sensitivity of each antenna.”

“I think it’s also neat that this is a hybrid eclipse, that is - it shifts from the annular to the total and back to the annular phase again, which is extremely rare,” she said. 

As morning activities continued, the Sun slowly started dimming, as the Moon moved across its face. Back here, on Earth, the Moon’s shadow was falling upon our home planet - commencing in the southwest Indian Ocean before moving in a northeasterly trajectory towards the equator. Satellites looking down from Earth’s orbit, such as Himawari-9 and DSCOVR, observed the dark, smudgy shadow that looked like a stain on the surface. When it crossed onto Australia, the continent fell into a deep, amber red. 

At around 11:20 am, as Melayne, Prof. Horner and Dr Moss looked skyward, the surrounding light of day around them started to now noticeably change. Light and shadows, coming in between the gaps of trees started to resemble hundreds of tiny shimmering eclipses. Wildlife started to retire for the day, confused by the darkness, and the air temperature cooled as a gentle breeze blew. 

As the Moon moved closer into its expected position, a small red crescent of light slowly shrunk down to thinner and thinner portions, and then it happened. Like a piece of a puzzle, everything seemed to click into place. The stars and planets emerged, as humans clapped, cheered and howled to the Moon, now surrounded by a bright ring of diffuse light - the solar atmosphere which only becomes visible during a total solar eclipse. The moment 20,000 people and millions around the world had been awaiting. 

Totality. Darkness. Eclipse.  

Science Check - Eclipses

The two different types of eclipses. A solar eclipse occurs when the Sun’s light focuses the Moon’s shadow onto a small region of Earth. Whereas, a lunar eclipse occurs when the Moon moves into the Earth’s shadow. Credit: Encyclopedia Britannica.

Eclipses are transient astronomical events that occur when three bodies align, causing a temporal obscuring of one of the bodies by another. The technical term for this is syzygy (a straight-line configuration of three astronomical bodies). Eclipses can be of natural objects, like planets, moons and stars, or human-made objects like satellites in orbit. Whilst humans have only ever seen an eclipse from Earth, robotic explorers on Mars have seen the transit of the moon Phobos across the solar disc from the Martian surface, and many astrophotographers, have captured the shadows of Jupiter’s Galilean moons falling onto its gaseous cloud surface, as well as onto other moons in the Jovian system causing Jovian eclipses. Astronomers also observe eclipsing binary star systems located thousands of light years away from us. The most commonly known eclipse to most of Earth’s inhabitants (humans and animals) is when there is an alignment between the Sun, Moon and Earth (with Earth’s inhabitants being the witnesses to such events). 

The two types of natural eclipses seen on Earth are solar eclipses and lunar eclipses. During a solar eclipse, the Moon’s orbit crosses between the Earth and the Sun, blocking out light from the Sun and causing the shadow of the Moon to fall (and move) upon the Earth. This shadow is focused on a region of Earth that is very narrow (relative to the rest of the planet) and races across the surface as the Moon moves along in its orbit. This is known as the path of totality, and if this path passes over an accessible region, people often will travel to see the event. The focused shadow region (the path of totality) is known as the umbra, but surrounding this is the region of the penumbra, in which a partial solar eclipse will be experienced - and this covers a much larger geographical footprint on Earth’s surface. 

Solar eclipses are able to occur as a result of a viewing coincidence from the Earth’s surface, and the time that we live in. The ability of the Moon to block out the entire solar disc from our perspective is due to it being 400 times smaller than the Sun, but also, 400 times closer. As such, the lunar and solar discs appear to be roughly the same size in our skies, and so, when the two overlay, one completely blocks out the other. 

Though, this will not always be the case. The Moon is slowly moving away from the Earth (at a rate of approximately 4 centimetres per year), and so in, about 600 million years from now, it will be at a sufficient distance away from Earth’s surface to no longer be the same size as the solar disc. Instead, it will be slightly smaller, meaning that only annular solar eclipses will be able to be witnessed thereafter. 

Our celestial neighbour, the Moon, bathed in red light refracted through Earth’s atmosphere during the May 2021 lunar eclipse over Sydney. Credit: Ángel López-Sánchez.

A lunar eclipse occurs when the Moon, once again along its orbit, passes into Earth’s dark shadow, so it is no longer able to reflect the Sun’s light. Instead, the Moon slowly begins to darken with a typical ‘round chunk’ taken out of it (this is the edge of Earth’s shadow), and as the Moon slowly moves deeper into the region, it begins to turn a blood-red colour (infamously now colloquially known as the ‘blood moon’). This colour arises as a result of Earth’s atmosphere acting like a giant lens, and refracting red light inwards to the central region of the shadow, causing it to fall upon the Moon. Effectively, it is a projection of every single sunrise and sunset on Earth at the moment, onto the lunar surface. 

Historically, both solar and lunar eclipses have been observed and recorded since ancient times, such as those meticulously documented by the Babylonians to a high degree of mathematical accuracy. In those ancient times, astrology was the main form of science (over astronomy), and so prediction models of future eclipses were made, as they were thought to be omens from Gods, or as part of mythological lore. Records of such events by cultures like the Babylonians were later used to learn more about the heavens (as part of astronomy) and allowed Johannes Kepler to provide a sound scientific explanation of these events in the 17th Century. 

On average, solar and lunar eclipses occur about twice per year, but there are some years with less and some with more. However, the populations that witness either event vary. This is because during a solar eclipse, the lunar shadow (the umbra) is focused on a very small portion of Earth’s surface, and so totality can only be seen by those in its path. Many people will witness a partial solar eclipse due to the penumbra shadow falling upon them. When this occurs over populated areas, more people will witness the total or partial solar eclipse, but because a large portion of Earth’s surface is also inhabited by few people (e.g. oceanic regions, Antarctica), many total or partial solar eclipses are only witnessed by a small number of people. A single location on Earth will likely only see a total solar eclipse (i.e., in the path of totality) once every three to four centuries. 

Lunar eclipses, however, are a different story. Because the full Moon can be seen by an entire hemisphere of Earth, then anyone with a cloudless night sky can observe Earth’s natural satellite as it moves into Earth’s dark shadow, before becoming turning to its infamous blood-red colour. 

Chasing Australian Eclipses

The diamond ring of totality, captured at the 2023 Exmouth eclipse. Credit: M. Wawrik.

Millions of dollars were injected into the local economy at Exmouth (and along the Western  Australian coastline) to prepare for the influx of global eclipse chasers, with authorities stating that they were pleased with the outcome. Not only were Australians from all over the nation there, so to were officials from NASA, Astronauts from Europe and other high-profile officials from around the world. All of this effort was, by all accounts, well worth it - and has likely inspired a new generation of scientists who will always remember their first-ever eclipse. 

“It was amazing and magical to see the eclipse in its totality,” said Melayne. “Honestly, it was one of those goosebump moment and even very, very emotional. It went from being hot and bright, to being cold and dark - even the wildlife was acting out of character during totality”

Prof. Horner, aboard the cruise ship, also described the experience as rewarding and exhilarating. “The atmosphere was amazing - hundreds of people there to see the same event,” he said. “Anticipation and excitement before, exaltation during as many on the boat called towards the skies, and then joy and satisfaction afterwards.” 

“I got to share the experience with my parents (who are in their late 70s - and have never seen an eclipse) as well as with colleagues from the Astronomical Society of Australia. Totality was too brief of course - less than a minute. But I suspect had it been an ultra-long, seven-minute eclipse, it would still have been too brief. Such a rewarding proper taste of totality for me too - it was breathtaking!”

An innovative way to look at a solar eclipse - repurposing a Pringles jar to act as a pinhole camera, projecting the partial eclipse for safe viewing. Credit: V. Moss.

Gaps between the tree branches project hundreds of shimmering eclipses onto the surface during the partial eclipse. Credit: V. Moss.

For Dr Moss, seeing the partial eclipse was only part of the reason for her visit to Western Australia, as the event also provided the opportunity to be with her cross-country team to conduct science with ASKAP (though, the telescope can be operated remotely from anywhere in the world). She was overseeing the control and management of the 36 dish antennas located some 800 kilometres north at Inyarrimanha Ilgari Bundara, the CSIRO Murchison Radio-astronomy Observatory. The science experiment was conducted to learn more about interplanetary scintillation and to see what an eclipse looked like through the ‘radio eyes’ of the ASKAP telescope from end to end. 

“We had two teams, the interplanetary scintillation (IPS) team and CRACO commissioning team observing radio sources around the Sun during the peak eclipse, where the obscured Sun was expected to reduce solar effects on the scintillating sources and potentially enable much better calibration/science to be extracted from the data,” she said. 

“Scintillation is similar to how the Earth’s atmosphere makes the stars appear to twinkle – scintillate – but the twinkling of galaxies ASKAP will observe is caused by the solar wind – charged particles emitted from the Sun – that can cause aurorae but also interfere with satellites.”

It’s expected that the solar effects will be reduced when the Sun is obscured during the eclipse, allowing scintillating sources - such as those distant twinkling galaxies - to potentially be better calibrated, and better science data extracted. 

Additionally, ASKAP was taking low-frequency radio observations of the eclipse from end to end, with data being processed in almost real-time by Dr Moss’s colleagues (located back in Sydney). At these frequencies, ASKAP doesn’t see the solar disc as our eyes do, instead it sees the radio emissions from active regions, known as sunspots. 

The Moon itself is an intervening body, and so, as it approached the sunspots and covered them, ASKAP could see the radio emissions from these regions blink off when the Moon passed over them, and then come back once the Moon had moved ahead in its orbit. Effectively, ASKAP saw the eclipse in radio light as well.  

The 2023 Exmouth solar eclipse, as seen from space over the Australian continent. The dark-shaded area over the Western Australia shelf is the Moon’s eclipse. Credit: Himawari-9 / JAXA.

Even though totality at this year’s Exmouth solar eclipse only touched the edge of the continent, the Australian public is in for a huge treat in the not-too-distant future. On the 22nd of July 2028, a total solar eclipse will cross the entire continent - starting in the northwest and heading southeast, before moving over the south island of New Zealand. Along the path of totality are towns and cities like Tenant Creek in the Northern Territory, Bourke, Dubbo, Orange, Bathurst,  the Blue Mountains, Sydney, Wollongong, Newcastle in NSW, and Queenstown and Dunedin in New Zealand. A partial eclipse will be visible to everyone in Australia, New Zealand, Indonesia and Papua New Guinea, along with several Pacific nations. It is estimated that over 600 million people will experience the event (provided the skies are cloudless). Already, people are starting to keep the date in mind and consider planning to catch this event. 

Australia will also see an additional three total solar eclipse events (either under the path of totality or a partial eclipse) in the upcoming decade, on 25th November 2030, 13th July 2037 and lastly on 26th December 2038. 

Everyone who has ever experienced a total solar eclipse never forgets it, and automatically becomes addicted to seeing more of them. With the Exmouth eclipse kicking off a series of upcoming total solar eclipses for Australia (and several lunar eclipses), a new wave of young science enthusiasts, amateur and professional astronomers, and interested members of the public will get a chance to have their first ever view of astrophysical events that have left humans in awe for thousands of years. 

Let the eclipse chasing begin. 

Solar eclipses over the Australian continent between 2001 - 2050. Credit: M. Zeiler / X. Jubier.