De Tal Palo, Tal Astilla (Chip Off the Old Block)

By Dwayne O'Brien

Published: March 16, 2006

There it is!” says Keivan Stassun, who has finally found what he is looking for.

As an astronomer, Stassun is trained to spot things before anyone else: long-sought objects that finally come into view after many twists and turns. Many times, it's a comet, an asteroid, a galaxy. But this time, it's a small dry cleaning shop nearly lost among a maze of new construction and beehive of activity.

Stassun has come to pick up his laundry before leaving Nashville later in the afternoon on a quick trip to Hawaii for two nights of observations at the W.M. Keck Observatory perched atop 13,000-foot Mauna Kea on the Big Island.

As an assistant professor at Vanderbilt University, Keivan Stassun is a man on the move and on a mission. He is quick to laugh, incredibly driven, committed to his discipline and seemingly in constant motion. A person can't hang around with the 33-year-old Stassun very long without discovering his passions for finding and exploring other worlds and for making a difference in this one or his conviction that science can accomplish both.

The latest Keck trip is to collect more data on an extremely rare pair of eclipsing brown dwarfs, the first ever observed. Its discovery, made by Stassun and his collaborators, is the result of years' worth of painstaking research and data analysis. Though finding a pair of small, failed stars 1,500 light-years away that happen to periodically pass in front of each other along the line of sight to Earth was difficult and a giant leap forward in the understanding of these dim substellar objects, in many ways the remarkable discovery is the least remarkable part of the story: a story that begins in southern Mexico.

El Norte

"My mother's name is Luisa...Luisa Flores,” Stassun says. "She was born in the south of Mexico in a very poor village where there was no electricity and no running water.” There was also very little hope. "She was one of ten children and grew up in a house made of dirt...literally made of dirt.” Luisa and the entire family worked as what we would call sharecroppers, growing and harvesting sugar cane.

"She had a poor and difficult childhood,” Stassun says. "I think that kind of background creates a very, very strong desire to get out of it. She became determined to work her way north to the 'Promised Land' of the United States. She hoped to find a better life in 'el Norte,' and that's what she did. She entered the country at the age of 20 and did what single Mexican women in the United States did at that time: she worked cleaning homes in the L.A. area.”

Soon thereafter, Luisa found herself expecting a child. "She was all alone and didn't speak the language, so she returned to Mexico to get back with her family and get that support there,” he says. "She also moved the rest of the family closer to the United States to just outside of Tijuana.” A few weeks before Keivan's birth, Luisa made the decision to return to the United States. "This was a difficult decision for her,” Stassun says. "Entering the country was, well, not exactly easy. But she realized that she had the opportunity to have her son born an American citizen. I was born in the L.A. area only a few days after she crossed the border.”

Though mother and son were now in the "Promised Land," life was not without hardship. Since Keivan's father was not in the picture, Luisa was left to raise him alone. "My father was Iranian, and Keivan is an old Persian name for Saturn. The funny thing is that I didn't learn the astronomical meaning of my name until after I had decided to become an astronomer,” he says. The moniker is the only tangible link to his paternal roots. "I never knew my father, so that part of my heritage I just never had much opportunity to connect with. My Mexican heritage, on the other hand, is one I relate to very strongly.”

Stassun was raised bilingually and speaks both Spanish and English fluently. He and his mother lived alone in the beach town of Venice, California, where she worked cleaning houses and they survived on food stamps and welfare. She also began working on earning her high school diploma. Those lean early years were formative. "I attribute much of my drive in academics to my earliest memories of my mother studying late into the night for her high school equivalency, and then later, for her citizenship,” Stassun says. "My mother is extremely proud of her status as an American citizen, and that has always had a powerful influence on me as well.”

His mother married his German stepfather when Keivan was seven years old, and the family moved to a working class neighborhood in the San Fernando Valley. Keivan took his stepfather's name of Stassun as his own when he was 11. "Putting my entire name together, there is sort of a fossil record of who I am,” he says. "Keivan Guadalupe Stassun. The Persian astronomical name; Guadalupe is my maternal grandmother's name; and Stassun is my German stepfather's name. I suppose it's a very American name.”

Top gun

"I guess I would say that I knew very, very early on that I was sort of hard-wired to do some kind of science,” Stassun says. "As a very young child, I was fascinated with all things science.” He showed an aptitude for mathematics and at a young age was already on a sort of math and science track. How astronomy specifically entered the picture was a little more indirect.

"What happened was that as a child I really locked onto the idea of becoming an astronaut. I was very serious about it. All through middle school and high school, I was focused on the idea ...passionate about the idea,” he says. After doing a bit of research he concluded, either correctly or incorrectly, that the best way to become an astronaut was to become a military pilot.

Stassun devoted a lot of time and energy to that effort and was successful. He was offered admission to the United States Naval Academy in Annapolis, Maryland. Upon receiving the actual offer of admission, however, Stassun began having second thoughts: "I had been so narrowly focused on that idea for so long that it wasn't until I was offered admission that I really stopped to think about what that would mean for my life.”

At the last minute, Stassun declined the offer and went instead to the University of California, Berkeley on a full scholarship. "Then I was faced with the decision of 'What do I do now?' I had been focused on becoming an astronaut for so long and now I had to decide what to do with myself. Astronomy, astrophysics.... I decided that if I couldn't go up there, I'd choose a profession that would allow me to stare up at the sky and wonder and ask those kinds of questions. In retrospect, I think I made the right call.”

On Wisconsin

After Berkeley, Stassun left the warm environs of southern California for graduate school at the University of Wisconsin in Madison. The young Californian took right to his chilly new surroundings. "Growing up in L.A., I was never into pro football but I was a huge Dodger fan: Fernando Valenzuela's rookie year and all that. Oh yeah, that was the time,” he says. "But when I moved to Wisconsin, I found that there's no such thing as not being a fan of the Green Bay Packers. Between the Packers and the cheese and the beer, I became a full-blown Wisconsonite.” A yellow foam cheese head cowboy hat still hangs in his Vanderbilt office: a silent tribute to good times had while cheering on the Pack.

Another legacy of Stassun's time in Wisconsin is his relationship with Robert Mathieu. Mathieu was his doctoral advisor at the University of Wisconsin and remains his closest scientific collaborator since he came to Vanderbilt in 2003. It was under Mathieu's mentorship that Stassun initiated the project that led to the discovery of the eclipsing brown dwarf system. It was, in effect, a successful search for a failure.

Needle in a haystack

Stars are born when huge clouds of interstellar gas and dust coalesce and collapse under the weight of their own gravity. Brown dwarfs are essentially "failed stars”: rotating balls of gas and dust that lack sufficient mass (about 75 times that of the planet Jupiter) to create the heat and pressure necessary in their cores to begin fusing hydrogen into helium, the nuclear process that powers true stars.

These substellar objects are difficult to detect not only because of their small size, but because they emit very little light. What light they do produce is largely in the infrared and results from the heat produced by their gravitational collapse. In effect, brown dwarfs do not "shine.” They merely "glow.” Finding one is difficult; finding a pair that actually eclipse one another as seen from Earth is very rare indeed and was not just luck. It was the result of diligent searching over a long period of time: Twelve years to be exact.

"The project to find something like this eclipsing brown dwarf system was really a 'needle in a haystack' project,” Stassun says. "We knew that somewhere in the universe there was likely to be something like this system, so we took the approach that if you're looking for a needle in a haystack, then you need to start sifting through haystacks.”

In this case, the haystacks were the stellar nurseries in our galaxy: those places where stars form in large numbers and where large numbers of brown dwarfs should also be present. The research team, made up of Stassun, Mathieu of the University of Wisconsin, Jeff Valenti of the Space Telescope Science Institute in Baltimore, Maryland, and Stassun's students began searching through the database of the brightness measurements for thousands and thousands of stars in these nurseries to see how the light they emitted changed over time.

The brightness of most stars changes very slowly, if at all. A small percentage of stars are variable; their brightness fluctuates over time. But the light curve is smooth and uniform — like a sine wave. What Stassun was looking for was the tell-tale "spike” of an eclipsing binary: a sudden, sharp dip in brightness caused when one of the pair crosses in front of the other, blocking some of the light: a "signature” that looks similar to an EKG.

Five years into the search, Stassun came across the data for a particular system that he thought might have that the desired signature. However, it took another seven more years of data collection and analysis to confirm that they had indeed found an eclipsing brown dwarf binary. In a haystack 1,500 light-years away in the star-forming region of Orion, they had found their needle.

Eureka

True eureka moments are rare in science. Most discoveries reveal themselves in gradual, stepwise progression; becoming more clear and definitive over time. Such was the case with this discovery. Stassun's team had suspected for several years that this system was indeed what they had been searching for, but the data was spotty and inconclusive. That's not to say there wasn't a moment when it all came together. It could not have had more theatrical timing.

Stassun remembers it well: "I had been invited to give a presentation at a conference on searches for this kind of system. I was pretty sure that at that point that we had found one of these rare eclipsing brown dwarf systems, but I wasn't 100 percent sure. I remember an hour before my presentation I was sitting in the conference hall while those were speaking before me and I was working with the data that I had on this system on my laptop. It was there in the lecture hall that it all locked in and I saw that perfect EKG signal.”

Stassun wanted to jump up and scream, but being in the middle of a lecture hall surrounded by people, he thought better of it. "I just sort of screamed internally, made a printout of the signature, and got it into my presentation. I went up, gave my presentation, and then announced the discovery of this exciting system and it had literally happened in that same lecture hall. Sometimes, it just happens that way.”

Making a difference

One of the aspects of Stassun's work that he is particularly passionate about is introducing others — particularly young people and minorities — to the excitement of astronomy. "I think that most people have a natural wonder for the sky, for the universe,” he says. "So tapping into that is a way of drawing in more of our native domestic talent to the scientific and technical workforce.” Stassun sees it in patriotic terms: "The fact is that, in order for the United States to maintain its competitive edge in an increasingly global and technology driven marketplace, we are going to have to tap into the full talent of all our citizens,” he says.

Stassun points out that there are, historically, entire segments of our population that have not developed the scientific talent to enhance our science workforce. "In some sense, I represent part of that, " he says, "and one of the specific things that I've been doing, now that I've moved to Nashville and work at Vanderbilt, is to develop programs that facilitate the training and inclusion of members of ethnic minority groups, women and other people who have traditionally been underrepresented in the sciences.”

De tal palo, tal astilla

Stassun continues his study of the eclipsing brown dwarf binary as well as exploring all aspects of stellar formation. In 2004, Stassun married his wife Justine. "I married a beautiful, intelligent woman from North Carolina. She's the love of my life.” Stassun's mother and stepfather still live in southern California, "and they're as proud of me as parents can be,” he says. "She used to say to me 'de tal palo, tal astilla' which is best translated 'chip off the old block'. That is a real gift: to have the pride and support of one's parents. That will carry you a long way.”

Clearly, Stassun's drive and determination is rooted in his past. " In a very real and deep way, who I am now as a professional, as an academic, as a scientist, is fed by that very same current that goes all the way back to the south of Mexico. It flows north through the southern California border and ends up in Nashville, Tennessee, of all places. It is a passion for making the world a better place. It is a passion for representing my people, my family; doing right by them.

"One of the things that I more recently in my adult life have come to understand is that, in America, this is a very average story.”