What Baby Stars and Meteorites Can Tell Us About Our Solar System’s Past
Rachel Smith studies the birth of stars to better understand the origins of life on Earth, and perhaps elsewhere in the universe.
Image: Lindsay Blatt/Motherboard
THE MOST UNKNOWN is Motherboard's love letter to the scientific process. For the next nine weeks, we'll be profiling the people trying to answer science's most difficult questions. Our feature-length documentary is now available on Netflix, and bonus episodes are available on YouTube.
When Halley's Comet last hurtled by Earth in 1986, a young kid named Rachel Smith was there to see it from one of the best astronomical viewing sites in the world.
Her father, an astronomer, kept telescopes at their New York home, so Smith was accustomed to staring at planets and stars, and imagining what they might look like up close. But when the family flew 5,000 miles west to Hawaii for the express purpose of viewing the comet, Smith was especially wowed. It wasn't just the rare sight of the cosmic visitor that impressed her, but the remote tropical landscape from which it was so brilliantly visible.
Decades later, Smith still regularly makes that very same pilgrimage from the East Coast to Hawaii so that she can stargaze from such an ideal location. She still wonders what those distant celestial vistas might look like, but now, as the head of the Astronomy & Astrophysics Research Lab at the North Carolina Museum of the Natural Sciences (NCMNS), she has much more advanced means to pursue those questions.
Fascinated by the mysterious chemical evolution that drives star birth and the formation of planetary systems, Smith captures light from baby stars through the eyes of the 10-meter Keck Telescope that sits atop Mauna Kea at 13,800 feet in elevation.
“[Mauna Kea] is one of those places on Earth where it almost feels like you’re a little off-planet to me,” Smith, who is also an associate professor in the Department of Physics & Astronomy at Appalachian State University, told me. “It’s just an awesome place.”
As one of the subjects of Motherboard’s documentary The Most Unknown, which follows scientists as they shadow researchers in other fields, Smith returned to Mauna Kea’s dizzying heights to show Montana State University astrobiologist Luke McKay around the Keck facility. The astronomers who use Keck spend nights remotely combing through its observations at headquarters in the nearby town of Waimea, but Smith still makes the trek to the telescope whenever she can, often with her students in tow.
“I think it is really important—for myself too—to go to the summit before observing if possible,” she said, “It’s a big operation, and even as a scientist, it’s good to remember what that is, what we’re doing, and have that tangible connection periodically, rather than just go and use the interface, because it’s a big responsibility to be able to use the telescope.”
Indeed, astronomers have to jockey for access to major telescopes like Keck, and even if they secure a time slot, there’s no guarantee that weather conditions will be optimal enough to capture the intricacies of their observational targets. But all the uncertainty, competition, and sleep loss is worth it once fresh data streams in, to be integrated into our ever-evolving understanding of the expanse beyond our planet.
Each astronomer has “one tiny little piece of a big puzzle that we’re all trying to figure out,” Smith said. “How unique are we in the galaxy, if not the universe?”
“There’s nothing unique about the molecules we have on Earth, versus what we observe in space."
She uses instruments like NIRSPEC, a high-resolution spectrograph on Keck II, to capture light from “protostars,” young stellar objects that are coalescing into mature stars. In particular, she focuses on carbon monoxide and its isotopologues (versions of carbon monoxide with differing amounts of neutrons). While it’s most well-known as car exhaust, carbon monoxide gas also surrounds protostars, and is one of the wellsprings from which infant protoplanetary disks draw their molecular foundations.
Tools like NIRSPEC split light from these infant stars into lines that reveal the abundance and distribution of ingredients baked into stellar systems, which enables astronomers like Smith to make conclusions about their chemical evolution.
That might sound slightly esoteric, but it ties back into an enigma that has intrigued humanity across cultures and ages—the origins of life, both on Earth, and possibly elsewhere in the universe.
“Carbon is an element that’s fundamental to life as we know it, and fundamental to planets like Earth,” Smith told me. “So just generally, if we can understand any more details about carbon chemistry in forming planetary systems, that will overall inform our understanding of how planets form, and how life could form.”
Watching these young systems develop from afar helps astronomers constrain theories about star and planet formation, including the evolution of our own solar neighborhood. But Smith also studies more tangible lines of evidence here on Earth; in addition to heading up NCMNS’ astronomy lab, she also serves as the museum’s curator of meteorites.
Many of these extraterrestrial rocks date back to the solar system’s infancy, 4.5 billion years ago. By comparing their properties to the processes observed in other systems, astronomers are gradually piecing together a more cohesive picture of how star systems are born—while getting into bombastic fights with each other in the process.
“You’d be surprised the level of detail people argue about with these things,” Smith said. She’s witnessed arguments over something seemingly benign like the formation of chondrules, which are the grains inside the most common type of meteorites, escalate to a point that “is a little crazy.”
This resolve to address even the most minute questions reflects the importance of these breadcrumbs—hidden in sources like meteorites and light from distant stars—in reconstructing the story of how our world came to be, and why it is such a haven for life today.
These mysteries quite literally keep Smith up at night, and not just when she’s reading telescope data. After teaching her students about trippy ideas like the Fermi paradox—the contradiction between the assumption that alien life should be abundant on other worlds and our lack of evidence for it—she keeps mulling the ideas over long after she’s left the classroom.
“We don’t think we should be that unique, really, right? There’s no physics that’s different in our solar system versus other systems that we observe,” she said. “There’s nothing unique about the molecules we have on Earth, versus what we observe in space. All the ingredients are out there. And yet we’re the only planet [we know of] with life.”
This interests Smith not only from an astronomical point of view, but also because she is an animal lover. Before she earned her MS and PhD degrees in cosmochemistry from the University of California, Los Angeles, Smith trained to be a veterinarian, obtaining a doctor of veterinary medicine (DVM) from Cornell University. Though ultimately, she opted to pursue astronomy, her fascination with life in all its variations—from cuddly pets to extremophile microbes—still informs her work today.
“I’ve always wanted to be a scientist,” Smith said, “and exactly what kind of scientist took me a little while. But the truth is that my background in biology and veterinary medicine isn’t wasted, really [...] I do have this sense of life, and appreciation for life, both on this planet and beyond this planet.”
In The Most Unknown, Smith was paired with two scientists that shared this zeal for life’s “endless forms most beautiful,” as evolutionary OG Charles Darwin put it. After she showed astrobiologist McKay the ropes at Keck and its Waimea headquarters, Smith headed out to the research vessel Atlantis, off the coast of Costa Rica, to join California Institute of Technology microbiologist Victoria Orphan.
Orphan studies anaerobic microbes—organisms that don’t require oxygen for respiration—in methane seeps on deep ocean floors. To observe their habitat and collect samples, Orphan and her team use the research submersible Alvin, which can dive to depths of over two miles.
Smith, who is fascinated by the sea and scuba dives in her spare time, was visibly thrilled at the chance to accompany Orphan’s colleague, Temple University ecologist Erik Cordes, on one of Alvin’s trips to the seafloor. The dive lived up to her expectations not only as a window into the daily lives of other scientists, but also as a new view on her own research interests.
“First of all, getting into Alvin, it seemed like a spaceship to me,” Smith said. “You’re moving through an environment that no one has ever seen, which is awesome to me as an explorer—scientists are explorers—and I just felt like this could be Europa someday. This could be the experience of being in an alien world, and just exploring. I felt like it was one of the closest ways to being in space as you could get, and yet you are going the other direction.”
“I’d go again in a minute,” she added. “You can note that if they want to send me back.”
Smith, who dreams of visiting space someday, clearly relishes these opportunities to experience otherworldly frontiers, and to wonder what lies beyond the next horizon. Even after years of trawling through mountains of data and code collected about stars, looking for any patterns that might exist between systems, she still retains that childhood sense of wonder about the radiant objects that brighten the night sky.
“I do feel connected to the objects,” Smith said. “I try to remember that I’m looking at light from a massive star, say 20,000 light years away, and that’s really cool. Even as naive as it may sound as a scientist, it’s pretty cool that we can get a lot of information that has applications for our solar system, as it was forming four and a half billion years ago, from a little light that comes through telescope.”