Reaching for the Stars (and the Exoplanets)

NASA astrophysicist Christopher Stark (Ph.D. ’10, physics) is on a mission to broaden our horizons in space

Christopher Stark (Ph.D. ’10, physics) grew up in Mt. Pleasant, Iowa, a small midwestern town known in part for one of its most famous natives, James Van Allen, a physicist who was very influential in the development of space science in the United States and even graced the cover of Time magazine in 1959. 

“Van Allen discovered the Van Allen radiation belts around Earth and I feel like this was sort of common knowledge in Mt. Pleasant,” Stark explained. “I went to James Van Allen Elementary School and my parents happened to live in Van Allen’s childhood home at one point.”

You might think all that stellar influence would spark a childhood passion for astronomy or maybe even physics. It didn’t.Chris Stark Chris Stark

“In spite of those coincidences, I didn’t grow up wanting to be an astronomer,” Stark said. “I didn’t stargaze at night, I wasn’t big into science fiction and space travel, none of that.”

But Stark eventually decided to become an astrophysicist, inspired by a college lecture that quite literally changed his life.

“The lecture was about exoplanets,” he recalled. “I remember thinking it was unbelievable that we have the ability to detect planets around stars outside our solar system. It was like a lightbulb went off! I knew exactly what I wanted to do with the rest of my life.”

Since then, Stark has spent nearly two decades unraveling the mysteries of distant planetary systems and developing tools to study them. In 2020, after years of exoplanet research and mission design, Stark became deputy integration test and commissioning project scientist for the James Webb Space Telescope (JWST)—the biggest, most powerful telescope ever launched into space.

“It’s incredibly exciting,” Stark said. “Webb was designed to look in the infrared at the faintest galaxies that one would possibly imagine—galaxies so distant that you’re essentially looking back in time to the first stars and the first galaxies that were formed. It’s an amazing opportunity.”

Falling in love with physics

For Stark, growing up in a small town in Iowa was worlds away from a career studying extrasolar planets and planning missions in space. As a kid, he had plenty of energy and liked to build things, encouraged by his industrious parents.

“My dad was a carpenter by trade for quite a while, and I can’t remember a time when he and my mom weren’t working on a project,” Stark explained. “It’s difficult to recall being around the house and not helping them with something, like re-roofing their house or laying a limestone retaining wall.”

In 1999 when Stark enrolled at the University of Northern Iowa, physics and astronomy were the furthest things from his mind. He was taking economics and marketing courses, looking ahead to a career in business. At the suggestion of his brother, who was also majoring in business, Stark signed up for a course called “The Physics of Everyday Life” to fulfill the physical sciences requirement for his degree. He never imagined what would happen next.

“The class was all about the physics behind everyday things like frisbees, CD players and cellphones. I was enthralled, and I just fell in love with physics,” he recalled. “I was learning about the world in a way that I never experienced before.”

Stark immediately changed his major to physics and never looked back. His very first undergraduate physics class—and later, that memorable lecture on exoplanets—set Stark’s course toward the stars. In fall 2004, he began his Ph.D. in physics at the University of Maryland.

“What really appealed to me was that Maryland’s physics department was so flexible with what their students researched, like biophysics and chaos theory and astronomy, which is what I ended up doing,” he said.

For Stark, UMD’s proximity to major research centers in the D.C. area, including NASA’s Goddard Space Flight Center, was ideal. 

“I could literally drive 10 minutes to NASA and chat with people there at lunch to see if they had a research project that they would want me to work on,” Stark recalled. “I found my first opportunity to research exoplanets at NASA by doing just that.”

Gamma rays and debris disks

After his first summer at NASA working on the Fermi Gamma-ray Space Telescope, Stark started working with Mark Kuchner, an expert on debris disks, the hazy dust clouds generated by asteroids and comets around other stars. At Kuchner’s suggestion, Stark applied for—and received—a NASA fellowship that funded three years of his Ph.D. research. For Stark, graduate school provided a world of opportunities, not just in research but in academics as well. 

“There’s some level of knowledge from the traditional academics that you’re taught in grad school that sticks with you for the rest of your career,” he explained. “I don’t know that a day goes by that some aspect of orbital mechanics or quantum mechanics doesn’t enter into my thoughts.” 

After earning his Ph.D. in 2010, Stark moved on to a postdoctoral position at the Carnegie Institution of Washington’s Department of Terrestrial Magnetism and spent three more years studying debris disks around distant stars. Three years later, he returned to NASA Goddard as a postdoc working with Aki Roberge, a research astrophysicist in the Exoplanets and Stellar Astrophysics Lab.

“I had been a theorist and an observational astronomer and when I started working with her, I said, ‘I’ve been working in this field for seven or eight years now I really want to get into mission design work,’” Stark explained. “And she said, ‘Have I got a project for you!’”

At the time, Roberge was studying a future telescope concept that would detect and image exoplanets. To determine what kind of telescope and other instruments would be needed, she had to develop a tool that could predict how many exoplanets the mission might discover. 

“We talked through how we would develop this tool and it turned out that everything I needed to do that project, I had the pieces already,” Stark recalled. “Forty-eight hours later, after reading through published papers and a lot of coding, I came back to her with a functioning skeletal structure of how this would work, and I think it hit both of us that we were onto something big.”

On a mission: the James Webb Space Telescope and Beyond

Together, Stark, Roberge and their colleagues developed a mission optimization tool that’s still being used by NASA today and Stark moved full steam into mission design. By 2015, he’d been hired as an associate scientist at the Space Telescope Science Institute in Baltimore, where he helped guide the design of future space telescopes and worked on the JWST, a huge NASA project that was still years away from launch.

“I was part of the team that prepared to align the mirrors of JWST after launch,” he explained. “Those golden hexagons, they all have to be aligned to within a fraction of a micron to work like one large mirror. The alignment is an amazing process, to be able to move around and shape a mirror segment more than a meter in size with such precision.”

Stark returned to NASA in 2020, taking on a new role as deputy integration test and commissioning project scientist for JWST, which launched in December 2021 and is now orbiting the sun on its journey of discovery.

“On a day-to-day basis, we’re tracking the performance of the telescope and instruments, and making sure that all the information we need is available to understand how the decisions we make impact science as we go,” Stark explained. “Working on this mission is thrilling, it’s stressful. More than anything, it’s humbling. It takes thousands of talented people to put something like this together.”

Stark is all about putting things together, and not just space missions. After years of doing construction projects with his parents as a kid, he still has a passion for building things at home in his spare time. No project is too big or too complicated.

“At this point, it’s an obsession. Anything that I can build is fair game. Honestly, that may be why I ended up in the position I’m in at NASA,” he mused. “I think there’s an aspect of designing future space missions that helps satisfy my need to build.”

From Stark’s Ph.D. studies to his current work on the Webb, every research project and every NASA mission have brought him closer to the dream he’s had since his very first day at UMD.

“My goal is to help launch a mission that has the chance of finding another planet that looks like Earth, and maybe even has biosignature gases that could be indicative of simple life,” Stark explained.

Stark believes that mission will soon be a reality. And he can’t wait to be part of it.

“We have so many exciting missions coming up that get at fundamental questions that humans have been asking themselves for millennia. We’re going to fundamentally transform our understanding of our place in the universe,” he said. “The next few decades of astronomy is really going to knock your socks off.”

Written by Leslie Miller

Thomas Ferbel, 1937- 2022

Thomas Ferbel, a UMD visiting professor since 2013, died at his home on Saturday, March 12. He was 84.

Ferbel was born in 1937 in Radom, Poland. During the tumult of World War II, he and his family endured exile in a Russian gulag and later, a camp for displaced persons in Stuttgart. Eventually, Ferbel arrived in New York and received a B.A. in Chemistry from Queens College, CUNY, and his and Ph.D. in Physics from Yale University (where his favorite professor was Bob Gluckstern, later the chancellor of this campus and a professor of physics).Thomas FerbelThomas Ferbel

After a postdoctoral appointment at Yale, Ferbel accepted a faculty position at the University of Rochester in 1965.  While there, he received an Alfred P. Sloan Fellowship, a John S. Guggenheim Fellowship and an Alexander von Humboldt Prize.

He was elected a Fellow of the American Physical Society in 1984, and served as the U.S. program manager for the Large Hadron Collider from 2004-08.

In 2020, Ferbel described both his early years and his life as a physicist as part of the American Institute of Physics Oral History project. The transcript is available here:

New Perspective Blends Quantum and Classical to Understand Quantum Rates of Change

There is nothing permanent except change. This is perhaps never truer than in the fickle and fluctuating world of quantum mechanics.

The quantum world is in constant flux. The properties of quantum particles flit between discrete, quantized states without any possibility of ever being found in an intermediate state. How quantum states change defies normal intuition and remains the topic of active debate—for both scientists and philosophers.

For instance, scientists can design a quantum experiment where they find a particle’s spin—a quantum property that behaves like a magnet—pointing either up or down. No matter how often they perform the experiment they never find the spin pointing in a direction in between. Quantum mechanics is good at describing the probability of finding one or the other state and describing the state as a mix of the two when not being observed, but what actually happens between observations is ambiguous.In the figure, a path winds through an abstract landscape of possible quantum states (gray sheet). At each point along the journey, a quantum measurement could yield many different outcomes (colorful distributions below the sheet). A new theory places strict limits on how quickly (and how slowly) the result of a quantum measurement can change over time depending on the various circumstances of the experiment. For instance, how precisely researchers initially know the value of a measurement affects how quickly the value can change—a less precise value (the wider distribution on the left) can change more quickly (represented by the longer arrow pointing away from its peak) than a more certain value (the narrower peak on the right). Credit: Schuyler NicholsonIn the figure, a path winds through an abstract landscape of possible quantum states (gray sheet). At each point along the journey, a quantum measurement could yield many different outcomes (colorful distributions below the sheet). A new theory places strict limits on how quickly (and how slowly) the result of a quantum measurement can change over time depending on the various circumstances of the experiment. For instance, how precisely researchers initially know the value of a measurement affects how quickly the value can change—a less precise value (the wider distribution on the left) can change more quickly (represented by the longer arrow pointing away from its peak) than a more certain value (the narrower peak on the right). Credit: Schuyler Nicholson

This ambiguity extends to looking at interacting quantum particles as a group and even to explaining how our everyday world can result from these microscopic quantum foundations. The rules governing things like billiards balls and the temperature of a gas look very different from the quantum rules governing things like electron collisions and the energy absorbed or released by a single atom. And there is no known sharp, defining line between these two radically different domains of physical laws. Quantum changes are foundational to our universe and understanding them is becoming increasingly important for practical applications of quantum technologies.

In a paper(link is external) published Feb. 28, 2022 in the journal Physical Review X, Adjunct Assistant Professor Alexey Gorshkov, Assistant Research Scientist Luis Pedro García-Pintos and their colleagues provide a new perspective for investigating quantum changes. They developed a mathematical description that sorts quantum behaviors in a system into two distinct parts. One piece of their description looks like the behavior of a quantum system that isn’t interacting with anything, and the second piece looks like the familiar behavior of a classical system. Using this perspective, the researchers identified limits on how quickly quantum systems can evolve based on their general features, and they better describe how those changes relate to changes in non-quantum situations.

“Large quantum systems cannot in general be simulated on classical computers,” says Gorshkov, who is a Fellow of the Joint Quantum Institute (JQI)  and the Joint Center for Quantum Information and Computer Science (QuICS). “Therefore, understanding something important about how these systems behave—such as our insights into the speed of quantum changes—is always exciting and bound to have applications in quantum technologies.”

There is a long history of researchers investigating quantum changes, with most of the research focused on transitions between quantum states. These states contain all the information about a given quantum system. But two distinct states can be as different as can be mathematically despite being extremely similar in practice. This means the state approach often offers a perspective that's too granular to generate useful experimental insights.

In this new research, the team instead focused on an approach that is more widely applicable in experiments. They didn’t focus on changes of quantum states themselves but rather on observables—the results of quantum measurements, which are what scientists and quantum computer users can actually observe. Observables can be any number of things, such as the momentum of a particle, the total magnetization of a collection of particles or the charge of a quantum battery(link is external) (a promising but still theoretical quantum technology). The researchers also chose to investigate quantum behaviors that are influenced by the outside world—a practical inevitability.

The team looked at general features of a possible quantum system, like how well known its energy is and how precisely the value they want to look at is known beforehand. They used these features to derive mathematical rules about how fast an observable can change for the given conditions.

“The spirit of the whole approach is not to go into the details of what the system may be,” says García-Pintos, who is also a QuICS postdoctoral researcher and is the lead author on the paper. “The approach is completely general. So once you have it, you can ask about a quantum battery, or anything you want, like how fast you're able to flip a qubit.”

This approach is possible because in quantum mechanics, two quantities can be intricately connected with strict mathematical rules about what you can know about them simultaneously (the most famous of these rules is the Heisenberg uncertainty principle for a quantum particle’s location and speed).

In addition to their new limits, they were able to reverse the process to show how to make a system that achieves a desired change quickly.

These new results build upon a previous work(link is external) from García-Pintos and colleagues. They studied classical changes such as how quickly energy and entropy can be exchanged between non-quantum systems. This previous result allowed the researchers to break up different behaviors into quantum-like and non-quantum-like descriptions. With this approach, they have a single theory that spans the extremes of possible outside influence—from enough interaction to allow no quantum behavior to the purely theoretical realms of quantum situations without any external influence.

“It's nice; it's elegant that we have this framework where you can include both of these extremes,” García-Pintos says. “One interesting thing is that when you combine these two bounds, we get something that is tighter, meaning better than the established bound.”

Having the two terms also allowed the researchers to describe the slowest speed at which a particular observable will change based on the details of the relevant situation. In essence, to find the slowest possible change they look at what happens when the two types of effects are completely working against each other. This is the first time that a lower bound has been put on observables in this way.

In the future, these results might provide insights into how to best design quantum computer programs or serve as a starting point for creating even more stringent limits on how quickly specific quantum situations can change.

Original story by Bailey Bedford:

In addition to Gorshkov and García-Pintos, authors on the paper include Schuyler Nicholson, a postdoctoral fellow at Northwestern University; Jason R. Green, a professor of chemistry at the University of Massachusetts Boston; and Adolfo del Campo, a professor of physics at the University of Luxembourg.

Bennewitz Named Finalist for Hertz Fellowship

Elizabeth Bennewitz, a first-year physics graduate student at JQI and QuICS, has been named a finalist for a 2022 Hertz Fellowship. Out of more than 650 applicants, Bennewitz is one of 45 finalists with a chance of receiving up to $250,000 in support from the Fannie and John Hertz Foundation.

The fellowships provide up to five years of funding for recipients pursuing a Ph.D. The foundation seeks(link is external) individuals who intend to tackle “major, near-term problems facing society.”Elizabeth Bennewitz (credit:  Dan Spencer)Elizabeth Bennewitz (credit: Dan Spencer)

“This whole group of finalists have accomplished so much, and I’m very humbled to be among other people starting their Ph.D.s who are also pursuing big problems in science,” says Bennewitz. “I'm very honored to be part of this finalist group.”

Bennewitz is working with JQI and QuICS Fellow Alexey Gorshkov and is interested in researching large collections of interacting quantum particles—what scientists call many-body quantum systems. These systems are important to understanding cutting-edge physics and quantum computer technologies and can also be the basis of simulations that could provide insights into complex problems in physics, material science and chemistry.

“During my PhD, I want to develop tools and techniques that help harness the computational power of quantum devices in order to simulate these large quantum many-body systems,” Bennewitz says. “I’m excited to be pursuing this research at Maryland because of its commitment to quantum information and quantum computing research as well as its rich collaboration between theorists and experimentalists.”

Bennewitz is just at the beginning of her graduate student career, but she has already started investigating how quantum simulators might be used to understand the interactions of the particles that are responsible for holding the nuclei of atoms together.

“I'm very happy for Elizabeth, and I'm honored and excited that she chose to work with my group,” Gorshkov says.

An announcement of the winning fellows is expected to be made in May.

“I'm very thankful for all the opportunities I had before I got here,” Bennewitz says. “I would not be where I am today without the support and guidance I received from my professors and peers at Bowdoin College and Perimeter.”

Original story by Bailey Bedford: