Chapter 1: The Universe

In the rocky, dry hills of the remote Karoo of South Africa, the Khoisan people native to the region tell an origin story of the Milky Way. A small girl, dancing around a fire, throws embers into the deep black sky. There they remain, a blaze of light stretching horizon to horizon. A perpetual fire burning in the sky.

The Southern African Large Telescope, or SALT, was built to gaze into these skies, from atop a plateau nearly 6,000 feet above sea level, in the small village of Sutherland, South Africa.

“The darkest skies I have ever seen are in Sutherland,” says Eric Wilcots, professor of astronomy. “You can trace the Milky Way all the way to the horizon.”

This is what first brought him and others from UW–Madison to SALT—the largest optical telescope in the Southern Hemisphere. Dark, clear skies are essential for a telescope designed to peer into some of the deepest reaches of our universe, and in so doing, to look back in time.

“As we look at more and more distant objects, we see those objects as they were when that light was [first] emitted,” Wilcots explains. “We are listening to whispers millions of light years away.”

By collecting light from objects distant and near, scientists can record the history of our own celestial origins. The more light they collect, the farther back in time they can see.

Understanding the lives of galaxies

SALT was optimized to study the Milky Way’s nearest neighbors, two galaxies called the Large and Small Magellanic Clouds visible only in the Southern Hemisphere. Astronomers can use these galaxies, Wilcots says, to “get a sense of both the forest and the trees” because they are “close enough we can resolve individual stars, but far enough away that we can see how the whole ecosystem of the galaxy works.”

He and other scientists, like his graduate student Julie Davis, also use SALT to study the gases that swirl in and among these and other galaxies. As hot gases cool and condense, they form stars. Dying stars return gas back to galaxies and seed the environment with the materials necessary to form planets. Understanding how materials enter into and escape a galaxy is crucial to understanding a galaxy’s metabolism, and ultimately, the evolution of galaxies like our own Milky Way.

Astronomy is a path forward

Large telescopes like SALT are essentially “light buckets,” Wilcots says. “The bigger the telescope, the more light you can collect.”

SALT’s 11-by-10-meter array of hexagonal mirrors, 91 in all, allows astronomers to see far back into time and space by gathering large amounts of starlight and transforming it into data.

The light collected by the telescope’s mirrors passes through an instrument on the telescope known as a spectrograph, which “is to an astronomer as a scalpel is to a surgeon,” says South African Astronomical Observatory astronomer Lisa Crause. SAAO administers SALT.

Spectrographs are like sophisticated prisms that split white light into its component wavelengths, from red to green to indigo and beyond. Astronomers use this information to gain valuable insights into an object being observed—like a galaxy—from its composition to its age, distance, and even how its individual parts might be moving.

The spectrograph on SALT was built in UW–Madison’s Space Astronomy Laboratory and scientists there are working on the telescope’s next-generation instrument.

A long history of expertise

UW–Madison was invited to be involved with SALT because of its long history of expertise designing and crafting astronomical instruments.

“We were the first place known for doing photoelectric photometry, a technique for measuring the amount of light in the galaxy and quantifying starlight,” says Wilcots.

UW–Madison astronomy professor Joel Stebbins pioneered this technique in the 1920s and ’30s, utilizing the photoelectric effect, the concept for which Einstein won his Nobel Prize.

Stebbins helped recruit the faculty who would become leaders in developing and advancing astronomical instrumentation. Among them was Kenneth Nordsieck, emeritus professor of the astronomy department and the original designer of the Robert Stobie Spectrograph, named for SAAO’s former director.

The telescope saw its “first light” in 2005, capturing images that included a galaxy 30 million light years from the Milky Way. By then, UW–Madison had already begun to play a role helping train the next generation of South African scientists.

Science that can change the world

Since the fall of apartheid more than two decades ago, South Africa has embraced astronomy as one of its scientific pillars.

After SALT was commissioned, UW–Madison created the Wisconsin Teacher Enhancement Program to help train South African teachers in the years after apartheid and help contribute to the nation’s transformation. It brought South African teachers to Madison for several weeks in the summer to take science and health courses.

UW–Madison also helped train one of South Africa’s first black astrophysicists, Ramatholo Sefako, who studied under Wilcots in the early 2000s.

Now, local scientists like Lisa Crause (who is working on another future spectograph for SALT), are leading the charge to re-shape the future of South Africa through science. The telescope has even supported a tourism industry in Sutherland and boosted its economy.

For graduate student Julie Davis, pursuing astronomy has meant being able to follow her dreams and collaborate with people across the world.

“There is so much human effort that goes into this,” she says. “Hundreds of people came together to build this telescope. We are driven by curiosity. Regardless of the tongue we speak, we have a common language.”

Chapter 2: Life on Earth

The Makhonjwa Mountains, on the eastern edge of South Africa, are not particularly majestic. The highest peaks are just 6,000 feet above sea level. But these mountains, also known as the Barberton Greenstone Belt, happen to be among the oldest in the world. They were born on a cool and strange early Earth nearly 3.6 billion years ago. And they are one of the few places on the planet where evidence of ancient life can be found.

This is what brought UW–Madison professor of geoscience Clark Johnson to South Africa. Johnson and his collaborators around the world study Earth’s geologic past in order to better grasp when and how life on the planet began. They also hope to better understand where we are headed.

Rocks uncovered in these mountains have helped to tell part of that story, in part because they unravel some of Earth’s history with oxygen, a critical element in the tale. Oxygen transformed the planet from a mostly inhospitable, barren chunk of rock to a wildly diverse domicile for everything from bizarre single-celled organisms to complex animals like apes and people.

In 2013, Nicolas “Nic” Beukes, a South African geologist at the University of Johannesburg who has been a longtime collaborator of Johnson’s, was studying Barberton’s rocks when he and his team found something unusual. As Johnson recalls it, Beukes got in touch with him and said, “You have to come down and see this!”

This is what a rock can tell you

Much like astronomers, who can look back in time by capturing data from many light years away, geologists can peer back into Earth’s history by studying rock records that extend miles beneath the planet’s surface.

The key is to find rocks that have not had their records altered over time by high temperatures, pressures and mechanical forces, known collectively as metamorphism. Rocks like this can be found in South Africa, and Beukes has access to rare and deep (old) deposits to study.

That was how he came to possess the 3.2-billion-year-old richly colored, layered rock that Johnson traveled to South Africa to examine in 2013.

“Some layers have darker color, some pinkish, some lighter gray, made up of little granules of iron washed in from somewhere in the shallow part of the ocean,” Beukes explains. “Clark and his students discovered that these lighter [pink] layers have a different composition from ones that formed in deep water.”

Using methods to look at the complex geochemistry of these layers, they showed that the lighter layers once existed in a shallow sea shelf above a deeper ocean and contained evidence of oxygen. This oxygen could only have been produced by living organisms—in this case, microbes known as photosynthetic cyanobacteria.

“We didn’t know it was this exciting until Clark did his sophisticated analysis and we said, ‘See, this is what a rock can tell you,’” Beukes says.

Paving the way for complex life

Around 600 million years ago, just a blink of an eye by geologic time, oxygen became one of the predominant gases in Earth’s atmosphere. This coincided with an explosion of complex lifeforms in the sea, like soft-bodied jellyfish and bug-like trilobites. Later, primitive plants began to flourish on land and animals ultimately evolved on dry ground.

But oxygen—and life—were present much earlier. Johnson and Beukes focus on the rock record because “we would actually be missing the whole story if we only focused on Earth’s atmosphere,” says Johnson. “It was the last to be oxygenated.”

Once oxygen-based organisms appeared, “it was the most important biological innovation on the planet,” he says. It set in motion an evolutionary chain of events that ultimately led to the origins of modern humans, roughly 200,000 years ago.

“It’s important to understand the history of oxygen on Earth,” says Beukes. “It’s where we come from.”