From Hilo and Tokyo, Two Astronomers’ Paths Converged to Help Win the 2020 Nobel Prize in Physics

The 2020 Nobel Prize in Physics was awarded to Roger Penrose, Reinhard Genzel, and Andrea Ghez for the discovery of a supermassive black hole in the center of the Milky Way Galaxy. Devin Chu, from Hilo, and Shoko Sakai, from Tokyo, were part of Andrea’s team at UCLA, working with the prize-winning data that was gathered at Keck Observatory on the Big Island of Hawai’i!

This story talks about how one young boy from a small town, and one young girl from a big city, were supported by their local communities to pursue science, and how higher education enabled them to help achieve that prize. It is also a tale of serendipity, as their lives crossed paths twice, at Dartmouth College and at UCLA, along the way.

Growing Up with Early Interests in Astronomy

Both Devin and Shoko became interested in astronomy at an early age. Devin, a fifth-generation Chinese/Japanese American on Hawai‘i’s Big Island, grew up in the small town of Hilo. His mother would take him to the library to borrow books, and one about the solar system made a particular impression on him. “It was a picture book that showed pictures of the planets and it was something that got me really interested,” he recalls. In the third grade, he chose an astronomer’s career for the school project of creating a personal timeline. In later grades, he realized his community was rich in ways for students to engage with science and scientists. “There were a lot of really amazing opportunities, growing up in Hilo, for being interested in astronomy and science, and I’m really very grateful that I was able to pursue those opportunities and have a very supportive community behind me.” Besides attending education and public outreach events, Devin contacted local astronomers for ideas to work on for science fair projects: an eighth-grade investigation of light pollution, and, in later years, more highly data-driven projects such as on stellar spectra and taxonomy.

Part of Devin's timeline project in elementary school.
Part of the timeline from Devin’s elementary school project. photo by Michelle Sandell

Shoko was born in Tokyo and remembers that there wasn’t much to see in the night sky save for the Moon. When she was in the second or third grade, her parents took her to a planetarium, “very local, nearby, and it was a really good one. It’s still there, after 40 years.” She was hooked. The experience beneath a planetarium’s domed ceiling with hundreds of starry lights projected overhead was deeply moving. When she was 13, her father’s job had her family move to Toronto, presenting her with the challenge of learning a completely different language. Fortunately, the language of science and math are global and Shoko’s talents there shined, supported by a physics teacher who would let her and her friends work on additional experiments outside of class. When her family moved back to Japan in the middle of her senior year in high school, Shoko remained in Canada to finish and graduate. She attended Cornell for her undergraduate degree which was in physics, since they didn’t have a program in astronomy. At Dartmouth, she could focus on that subject exclusively at last.

Two Paths Converge: Dartmouth College

While a graduate student at Dartmouth, Shoko became more immersed in observational astronomy. She remembers that although it was a small department, it had great resources, like access to the MDM Observatory at Kitt Peak, Arizona (at the time operated by the University of Michigan, Dartmouth and MIT). It is comprised of two telescopes, a 1.3-meter and a 2.4-meter, where Shoko was able to acquire a great deal of observation time.

“It’s a small telescope, there’s literally no operators. It’s not like the Keck telescope where there’s operators and they’re doing everything and you request, ‘I would like to go to this sky.’ No, you had to do everything; there’s nobody else at the telescope. And sometimes things go wrong, and you’ve got to figure it out. ‘Do I call somebody down in Tucson? Do I wake them up? I better figure it out before I call and it turns out to be a really dumb mistake.’ But it makes you think; you’re dealing with this huge mechanical thing. I learned a lot just by being there for literally 150 nights or something like that in three years. For a graduate student, that’s an experience most can’t get.” Shoko also performed observations for two summers at the Arecibo Observatory in Puerto Rico.

Shoko’s PhD research concentrated on the three-dimensional structure of the universe, particularly focusing on the Perseus-Pisces cluster. This was a hot topic in the mid-1980s and early 90s, when groundbreaking data showed that galaxies were not evenly distributed across the universe. The data was initially represented as a flat, lace-like plot, and there was a need to better understand how the galaxies were located in terms of their distance from us: their three-dimensional distribution. And Shoko’s analyses here gained her recognition within the astronomical community.

She also counts herself lucky to have had Gary Wegner for her advisor at Dartmouth. In one of his projects, he collaborated with six other prestigious astronomers (informally dubbed the “seven samurais”). Their work included gathering data leading them to propose the existence of what’s called a “great attractor” toward which everything seems to be moving, which received a good deal of attention in the astronomical community. Since Shoko was working directly with Gary, within the friendly confines of a small school, she also made connections with other ranking members of the field. “Those astronomers would come to Dartmouth every summer to work together, and every summer we’d just chit-chat all the time so they knew me. So that was a kind of connecting into the astronomy world.” From witnessing their teamwork, Shoko recalls, “I learned the ‘fun part’ of a research collaboration. They loved astronomy and, at least to me at the time, they seemed to enjoy each other’s company so much, which was instrumental in keeping the collaboration going for a long time. It showed the positive side of doing astronomy: that it’s not just about staring at a workstation or observing all night long. There is a human side to doing science.”

Left to right: Andrea Ghez, Dr. Ciurlo, Devin Chu, and Professor Tuan Do, taking a break from observing the S0-2 star to test Einstein’s Theory of Relativity. photo courtesy of Tuan Do

Some 15 years later, the town of Hanover and its college attracted Devin, who was ready to leave his island nest. He remembers Gary Wegner, who would become his mentor, after one of his first physics classes. “He mentioned that, ‘Oh, as an astronomer I don’t deal with but maybe one of these concepts on a day-to-day,’ and it sort of ran in my head, like, ‘Oh, he’s an astronomer!’” At one of Gary’s first office hours, Devin introduced himself. “I think he thought I was there because I needed help on a problem set. But when I told him I was interested in astronomy he was very surprised by that, from what I remember. I don’t think there were that many students at Dartmouth at the time who went in and ended up majoring in astronomy, so I think he was delighted that there was a prospective astronomy major.”

Under Gary’s tutelage, Devin tried a variety of different research projects to figure out what he liked. He assisted Gary with an investigation into colliding galaxies and their rates of star formation. “I was helping do some of the data analysis for that. He laid the groundwork for me to see what it’s like to be aware of what types of astronomical objects there are, the science motivations for why these targets are interesting, how we test a certain hypothesis for it. I also got more of a hands-on experience of working with astronomical data: it’s you being on a computer all the time, not sitting with an eye on a telescope eyepiece!”

His Dartmouth education taught him that he preferred observation, rather than studies more steeped in engineering or mathematical astrophysics. With that intention, Devin set his sights on graduate school at UCLA.

Two Paths Converge Again: UCLA

UCLA’s department of astronomy and astrophysics focuses on the observational research that Devin favored, and he valued that the department prioritizes education and public outreach. He had spoken briefly with Andrea Ghez before attending, when he described research he had done with observations of Pluto. “Andrea at the time mentioned, ‘Oh, you’re interested in observing planets; you could think of the galactic center region, where instead of the Sun you have a super-massive black hole, and instead of planets, you have big stars around them.’”

Part of Devin’s work for the Galactic Center Group involved tracking the orbit of a type S0-2 star around the galactic center. Generally speaking, Newtonian physics predicts and describes the behavior of orbiting bodies just fine. But when extreme gravitational forces are at work, like around a super-massive black hole, objects and light behave in ways Newtonian physics cannot explain, but Einstein’s general relativity can. Devin’s task was to see if this S0-2 star exhibited characteristics incompatible with Newton physics, but were consistent with Einstein’s general relativity.

“When the star is pretty much closest to the black hole, essentially Einstein predicts that it should be redder than we would expect; you can think about it like the light is coming out of the gravitational well of the black hole. With Newtonian physics, we wouldn’t expect any kind of deviation, but Einstein’s general relativity predicts we would, and it predicts how red the star should be. That’s what we were able to do in 2018, which was really exciting.”

It takes spectroscopy to get the type of data needed to determine if a star’s light is red-shifted. Spectroscopy enables scientists to analyze the finer points of the light received from an object: its composition, its temperature, how fast it’s moving, if it’s moving toward or away from the observer, and how fast it’s spinning, for instance. Devin is skilled in this kind of analysis.

An example of spectroscopic data from a star (left), compared with stellar imaging data of the center of the Milky Way Galaxy (right). Spectrum image from; Milky Way image courtesy of ESA/Hubble and NASA, R. Cohen

Additionally, that data must be placed within a frame of reference, and that’s where Shoko comes in. “Whenever you do this kind of work you have to say, ‘This is the X axis, this is the Y axis.’ Otherwise, you can’t say where something is very accurately. ‘It moved this way.’ But what does that mean? Did it move two kilometers? Did it move 20 kilometers? You don’t really have a ruler on that map so my job is to figure out the most accurate map I can every year, and what the X and Y coordinates are. That’s all based on the imaging data.”

Shoko coordinates images of objects taken on Keck in the infrared, with other objects that are observable both in infrared and radio waves, based on radio data have been taken and analyzed independently by Mark Reid at Harvard University. With the orientation of objects in the radio wavelengths determined, then since those objects also observable in infrared, they frame the infrared objects that the Galactic Center Group studies, and they can understand how they have moved.

A simplified representation of the imaging work Shoko performs. The Galactic Center Group works with infrared data, and the objects that appear at those wavelengths in the galactic center are all in motion. Without a stable frame of reference, it is impossible to determine their location with the degree of necessary precision. Fortunately, masers (M1, M2, M3) in the galactic center also show up in radio wavelengths, along with galaxies (the spirals) that are so far away they display no proper motion. Since the galaxies can set a frame of reference for the masers, the masers’ positions can be exactly specified. With that locked in, the locations of the star (S), not observable in radio wavelengths, can be determined accurately, and its motion measured. graphic by Michelle Sandell

Shoko’s route to the Galactic Center Group was roundabout. For many years, she lived on “soft money”: she applied for and received science grants sufficient to support herself and her research. On the up side, she didn’t have to worry about the travail of securing tenure and a university salary. But it’s not an easy life. One has to keep track of funding deadlines, regularly write and submit funding applications, and frequently worry whether one’s money will last until the next grant comes in. It’s an exhausting and repetitive process, one that she took a hiatus from after marrying a UCLA astronomer and having children.

Visiting the campus one day, she encountered Andrea, who asked if she was interested in a job. She offered Shoko a role with the Galactic Center Group, one flexible enough to meet her needs. Shoko had to undergo an adjustment regarding the subject matter; she was accustomed to working with groups of galaxies separated by mega-parsecs of distance (one parsec is roughly equivalent to 19.2 trillion miles; “mega” means “multiply that by 1 million”). Now she was being asked to look at information within a single galaxy with measurements in astronomical units (1 AU = the distance between the Earth and the Sun, approximately 93 million miles). But her background proved she was experienced, and would be an asset for the team. “That was probably five or six years ago, just when Devin started; he was a first-year student, I think, when I started. So, I started in a completely new field, but I guess the bottom line is that I love doing astronomy, I loved joining the team.”

Devin Chu with his colleague, Anna Ciurlo, PhD, a research scientist with the Galactic Center Group, observing at Keck Observatory headquarters. photo courtesy of Tuan Do

Looking Forward

Now a postdoc at UCLA, Devin works to understand star formation in extreme environments, like around super-massive black holes. The general view in astronomy is that clouds of dust and gas collapse within a relatively stable environment until they condense into a star. But in extreme environments, shearing forces would seemingly constitute an environment too unstable for stars to form. But they do form. Data suggests that the young S0-2 star that Devin has tracked must have formed near its current location, and it remains to be explained how that happened.

Both Shoko and Devin are thankful for the Keck observations on Maunakea. That data made possible the prize-winning work to which they contributed. They also look forward to the future of astronomy in Hawai‘i with new instruments, especially with new technology like the Thirty Meter Telescope. Shoko says, “It would be nice to have a 30-meter telescope. We have had a 10-meter telescope for a while, and I think everyone is ready to go on to the next frontier, the next phase of astronomy, and see what we can do. I personally would like to do it in Hawai‘i.”

Devin reflects that, unbeknownst to him as he was growing up in Hilo, Andrea was already conducting observations on Maunakea that set the foundation for the work earned her a Nobel prize. In honoring his memories of how important science outreach was to him when he was young, he participates in outreach opportunities at UCLA, and is a mentor to Hawaiian students through the nonprofit organization PUEO (Perpetuating Unique Educational Opportunities). The Big Island helped Devin to become a professional astronomer today. He perceives the same situation for students now and in the future. “The potential of students here [in Hawai‘i] is incredibly high, and every time I come back and do educational outreach, I’m amazed by how bright and how curious and how interested the students are. That makes me feel really adamant about making sure these opportunities are there for them to further their interests are there.” 

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