How to Make a Solar System
What the world’s largest telescope is revealing about the birth of planets
What the world’s largest telescope is revealing about the birth of planets by Viviane Fairbank
One october day a few years ago, astrophysicist Sean Dougherty opened an email to find an astonishing image. On his screen was a sunlike star located about 450 light years away. Rendered in unprecedented detail, the bright yellow circle was surrounded by fuzzy rings darkening from orange to red with gaps interspersed in between.
The whole thing looked like a hot element on an electric stove.
What Dougherty was seeing, for the first time in such fine resolution, was evidence of new planets forming.
The image had been created thousands of kilometres away, in Chile, by the largest ground-based telescope array in the world. At the time, the observatory hadn’t been fully completed, and astronomers were just starting to grasp the worlds it would open up to them. For Dougherty, who was then working as the director of a small observatory in Kaleden, BC, just south of Okanagan Lake, the image of the star, which is called HL-TAU, was almost too beautiful to believe. It hinted at what the solar system looked like in its infancy, more than four billion years ago. And, because it showed the dark gaps that astronomers had predicted in their calculations, it was a landmark in the history of astronomy.
The telescope in Chile that produced the image is called the Atacama Large Millimeter/submillimeter Array (colloquially referred to as alma), and it is actually a collection of sixty-six antennas that are programmed to shift in sync, coordinated to follow an object as it progresses across the sky. Though they work together, the antennas are separate and mobile so that researchers can position them anywhere from 150 metres to 16 kilometres apart; they can be combined in thousands of possible ways to focus on different distances. (The main telescope at Dougherty’s Kaleden observatory had seven antennas — tiny by comparison.)
Set in the Atacama Desert of the Chilean Andes, at 5,000 metres above sea level, where the atmosphere is very thin, alma’s antennas are surrounded by some of the harshest environmental conditions on Earth. The rusted desert is dotted with ancient volcanoes and plagued by bitter winds and dust storms, with temperatures typically below zero. Conducting research here is not a simple endeavour: workers on the site, who move the antennas with tank-like specialized vehicles, are susceptible to UV radiation, and they are required to wear oxygen tanks. Moss colonies and the occasional animal — donkeys, llamas, and alpacas have all been spotted — are otherwise the only signs of nearby life.
The atmospheric clarity and the variability of alma’s antennas means they can explore the universe to an accuracy smaller than the thickness of a sheet of paper; if the astronomers using the array wanted, they could pick out a golf ball at a distance of fifteen kilometres. alma’s
ability to view distant objects, such as HL-TAU, that are still in the process of forming, makes it the most powerful tool at humanity’s disposal for understanding how our solar system came into existence. And, though he had no idea the day he first looked at that image of a distant star, Dougherty would soon be running the observatory that produced it.
Astar forms from collections of dense gas and dust in the universe. Some molecules collapse under gravity and become part of the star itself; others form what’s called a protoplanetary disc: a thin, wide swath of rubble surrounding the star. Over time, within that disc, astronomers had hypothesized, clusters of this rubble would meld together to become sand, pebbles — and eventually, asteroids, comets, and planets quite like our own. That’s what the dark circular gaps in the alma picture were letting astronomers see and confirm: nascent planets sweeping away debris as they orbited.
Astronomy is in many ways an exercise in visualization. Primitive astronomical observation, which began with the first telescope more than four centuries ago, was done using mirrors and lenses, zooming in on objects that could be seen with the naked eye. These are what we call optical telescopes. Early optical telescopes effectively extended the reach of our eyes: they enabled a person to see the kinds of things they could see anyway, just from farther away.
But, even with assistance, there is only so much our eyes can see. Light exists on a spectrum, from high-frequency gamma rays to low-frequency radio waves, and very little of that range is visible to us regardless of distance or proximity: our eyes aren’t built to capture it. Though humans can easily see the sun and other stars, which are extremely hot and so produce many frequencies of light, including some on the visible spectrum, we can’t see the majority of the cold, dark universe, with its temperatures near absolute zero and extremely low frequencies. The universe isn’t painted for human eyes.
To understand a distant object, astronomers need to pull together information from as much of the light spectrum as possible. So contemporary astronomers build antennas that can capture light waves at different frequencies — including ones our eyes cannot see. alma operates between the radio and the infrared, and it is designed to observe electromagnetic waves that are 1,000 times longer than those of visible light. The resulting data is sent via fibre-optic cables to the highest-altitude supercomputer in the world — which, with its 134 million processors, performs 17 quadrillion operations per second to combine and compare the antennas’ signals.
Six years after alma produced the first detailed image of HL-TAU, breakthroughs have become common. In late 2018, astronomers released high-resolution photos of twenty similar protoplanetary discs — discoveries that showed that large planets, such as Neptune or Saturn, likely form much faster than originally thought. Helen Kirk, a researcher at the Herzberg Astronomy and Astrophysics Research Centre, in Victoria, is interested in star formation. She and her research colleagues are focusing alma’s antennas on the core of certain molecular clouds, where stars may begin to emerge. “Someone had tried to do similar work before alma existed,” Kirk says. “They needed to stare at a single core for eight hours, and they couldn’t find anything. In alma, we get deeper and better images in less than two minutes.”
Dougherty, who is now fiftyeight years old, didn’t start out with any idea of being an astronomer. After growing up in West Yorkshire, in the UK, in the 1960s and ’70s, he studied physics and mathematics at university. In the 1980s, his love for mountainous landscapes led him to western Canada, where he eventually worked on new methods of searching for oil in Alberta. His specialty was reconstructing areas deep underground: with mapping software, he could help locate what he called “geological layers” — hidden troves of oil in the earth. After some time, though, Dougherty wanted more of a balance in his life and decided that
he needed to do something as far removed from making money as possible. So he went back to school and applied his methods to the heavens instead. As a PHD student in astrophysics, Dougherty specialized in radio astronomy, which employs similar methods to the ones he had used for oil exploration. “You’re trying to take sparse information,” he says, “and pull out the reality of the sky.”
One of the primary constraints on astronomy is that only a few places in the world are suitable for hosting telescopes capable of producing major results. Astronomers seek isolated areas at high altitudes, such as mountain summits, where the weather is calm and windless, the air is dry and cool, and the sky is clear of clouds, water vapour, and light pollution. Consequently, many major observatories on the planet are located in Antarctica, Hawaii, and Chile — places with the highest number of cloudless nights and little interference from human civilization. And, because sophisticated telescopes require a huge amount of money and resources, only a handful of these research facilities have ever been built.
This scarcity makes astronomy ahighly collaborative discipline, one in which scientists routinely work together internationally. alma, say researchers, is the best realization of this cooperative model yet. It was conceived of and created as a collaboration between space agencies in North America, East Asia, and Europe, with Chile as the host country. Christine Wilson, an astronomer at Mcmaster University, in Hamilton, was the Canadian project scientist with alma for fifteen years, helping to coordinate the array’s scientific undertakings as it was being built. “It is really the first,” says Wilson. “A world observatory . . . Almost all the major players are partners.”
This isn’t to suggest that the observatory’s launch was entirely smooth. When Dougherty saw HL-TAU, he was working as a new board member for alma — the only Canadian member in an international coalition of astronomers governing the new observatory’s operations. Though the telescope was already being pointed at the sky, the facility itself was still in the final stage of construction — the last antennas were still being tested. At the time, he says, there were tensions between different stakeholders, and Dougherty saw an opportunity for détente: “This,” he told his colleagues in an email, “is exactly why we built alma.” He spent the next two years heading the observatory’s budget committee. “I was seen as the friendly Canadian,” he says. “Neutral, happy, always fair — the classic Canadian cliché.”
By 2017, the observatory was operational and seeking a new director. Dougherty applied, buoyed by his successful experience running the budget, and he got the job. The next year, Dougherty moved with his family to Chile, leaving behind his small observatory in British Columbia to lead astronomers in the search for humanity’s cosmic origins. Of necessity, his job involves a lot more human resources and a lot less science than one might expect. “My day-to-day work is probably not so different to that of many other managers around the world,” Dougherty says. One of his primary responsibilities is overseeing a process that involves nearly 200 scientists who decide how to allocate precious research time at the observatory each year. “We get typically 2,000 proposals from around the world,” Dougherty says; they accept about 400.
At least once a month, Dougherty dons an oxygen tank and visits his crew in the desert. In his occasional spare time, he goes biking and climbing in the Andes, traversing the volcanic mountains that surround alma’s antennas. Dougherty loves hiking without an oxygen tank — a choice that alma’s safety team disapproves of — so he does it far from the observatory, where his colleagues can’t see him. Climbing in the Atacama Desert, where the sky is exceptionally clear, is a remarkable experience. “The stars come all the way down to the horizon,” Dougherty says. “It feels like you could reach out and touch them.”
Viviane Fairbank is a writer living in Montreal and the associate editor of The Walrus.