The Planet Hunters

Milky way

The Milky Way as seen from a telescope in the Namibian desert. (Photo courtesy of Gáspár Bakos)

From Gáspár Bakos’ desk at Princeton, he can see everything that happens at his telescopes on three continents. He can see wild burros nuzzle at the cables in Chile, warthogs wander by in Namibia, and kangaroos come a bit too close for comfort in Australia.

Despite the risks to his equipment, managing telescopes in three time zones across the Southern Hemisphere has a major advantage: it is always nighttime somewhere, so Bakos’ telescope network can search around the clock for planets outside our solar system, or exoplanets.

Bakos, an assistant professor of astrophysical sciences, is one of several Princeton faculty members involved in finding and studying exoplanets. Some researchers, like Bakos, are searching for the faint dimming of starlight that happens when a planet transits in front of a star. Others are trying to achieve what some have called the Holy Grail of planet hunting: direct imaging of an exoplanet. But detecting a planet is just the beginning. Researchers hope that by studying other solar systems they can confirm theories about how planets form and perhaps even learn whether life exists on these other worlds.

“Princeton is making contributions to the search for exoplanets in a number of areas,” said David Spergel, the Charles A. Young Professor of Astronomy on the Class of 1897 Foundation and chair of the Department of Astrophysical Sciences.

Discover and characterize

Just 20 years ago, finding planets around stars other than our sun was thought to be impossible — they were too far away, too dim and too close to the glare of their star. But today, due to creative strategies and new telescopes, about 1,000 planets have been detected and confirmed, with thousands of candidates awaiting confirmation.

The vast majority of the confirmed planets are quite unlike our own, however. Some are gas giants larger than Jupiter that orbit very close to their star — so close, in fact, that they can make an entire circuit around the star in a few days. Contrast this to our solar system, where Mercury, the closest planet to the sun, has an orbital period of 88 days — that is, it takes 88 days to orbit the sun. Earth makes the journey in 365 days.

The reason we’ve found so many of these large planets, which astronomers have nicknamed hot-Jupiters, is because they are relatively easy to detect with current methods. The two most successful ways of finding planets to date are to look for the periodic dimming of starlight when the planet crosses in front of the star, as Bakos’ telescopes do, or to look for the episodic wobbling of the star in response to the planet’s gravitational pull.

Professor Gáspár Bakos

Professor Gáspár Bakos (Photo by Pal Sari)

Through findings from a space-based NASA telescope known as Kepler, which hunted planets from 2009 until earlier this year, we now know that hot-Jupiters are the exception rather than the norm. “We can detect these hot-Jupiters because they pass in front of their stars fairly often and they block a significant fraction of the starlight,” said Bakos, “not because there are more of them than there are other kinds of planets.”

These other kinds of planets could include ones with conditions capable of supporting life. These planets lie in the “habitable zone” not too close and not too far from their star, and are capable of having liquid water on their surfaces.

One of Bakos’ telescope networks, HATSouth, is looking for exoplanets, including possibly habitable ones. HATSouth can detect planets with orbital periods of 15 to 20 days, which may not seem like much, but for certain classes of stars, namely the mid- to late-M dwarf stars, planets with 15-day periods lie in the habitable zone.       Bakos started building his first HAT — Hungarian made Automated Telescope — in 1999 while a student at Eötvös Loránd University in Budapest. The automated telescopes are relatively small — close in size to amateur models — but the lower costs allow more of them to be deployed. An earlier network Bakos built, HATNet, which came online in 2003 and consists of telescopes at sites belonging to the Smithsonian Astrophysical Observatory (SAO) in Arizona and Hawaii, has discovered 43 candidate planets.

HATSouth became operational in 2009 and is a collaboration between Princeton University, the Max Planck Institute for Astronomy, Australian National University and Pontificia Universidad Católica de Chile. Originally funded by the National Science Foundation and SAO, the network consists of six robotic instruments located at Las Campanas Observatory in Chile, the High Energy Stereoscopic System site in Namibia and Siding Springs Observatory in Australia. To date, HATSouth has detected a handful of planets, and has a dozen candidates awaiting confirmation. So far, all of the planets have fairly short orbital periods — they orbit their stars in one to three days — but Bakos is optimistic about HATSouth and his new project, HATPI, for which he has received funding from the David and Lucile Packard Foundation. HATPI is a wide-field camera system that will continuously image the entire night sky at high resolution and precision for five years, with the goal of identifying planets with longer orbital periods. Bakos’ team includes Joel Hartman and Kaloyan Penev, both associate research scholars; Zoltan Csubry, an astronomical software specialist; Waqas Bhatti and Miguel de Val-Borro, both postdoctoral research associates; and Xu (Chelsea) Huang, a graduate student.

Direct imaging

While HATSouth looks for dips in starlight that indicate the presence of a planet, other researchers at Princeton are aiming to directly image exoplanets. Such imaging is possible, for example, when the planet appears on the right or left side of the star rather than directly in front of it. To date, only a handful of exoplanets have been observed this way, because the star’s light is so bright that seeing a nearby planet is like trying to see a speck of dust in the glare of a headlight.

Kasdin

Professor Jeremy Kasdin (Photo by Alexandra Kasdin)

Jeremy Kasdin’s group is working to develop instrumentation for direct imaging. “The idea is to block out the star’s light so that it is possible to see the planet,” said Kasdin, a professor of mechanical and aerospace engineering.

Astronomers have used this concept to study the sun since the 1930s: they place a black disc, called a coronagraph, at the center of the telescope’s image to block light from the sun so they can study solar flares on its surface.

For planet-watching however, this light must be blocked with great precision. Because light acts as a wave, it diffracts around the edge of the telescope and, without a coronagraph, creates concentric patterns on the resulting image (see illustration, page 27), just as water makes ripples in a pond when it flows past an obstacle. These patterns obscure the planet.

To eliminate or change these patterns, researchers at Princeton’s High Contrast Imaging Laboratory, led by Kasdin, are developing a coronagraph with a distinctive shape and arrangement of slits that alter the patterns in ways that can permit detection of planets. This “shaped-pupil coronagraph” is being developed by Kasdin and his collaborators Spergel, Edwin Turner, a professor of astrophysical sciences, Michael Littman, a professor of mechanical and aerospace engineering, and Robert Vanderbei, a professor of operations research and financial engineering, along with postdoctoral research associates Tyler Groff and Alexis Carlotti and graduate students Elizabeth Jensen and A.J. Eldorado Riggs. The coronagraph could be sent up in a space-based telescope mission under consideration for later in the decade.

Pupil diagramThe Kasdin lab is also working on another light-blocking idea called an occulter. This is a giant sail that could fly in space, ahead of a space-based telescope, to block out light from a star. “It is sort of like holding your hand up to block the sun while you watch a bird in the sky,” said Kasdin. The occulter would be launched folded-up, like a flower bud with petals that would unfold in space to create a shield with a diameter of about 40 meters (131 feet) that would fly about 11,000 kilometers — or roughly 6,800 miles — ahead of the telescope to block the star’s light.

Occulter diagramAt Princeton’s Forrestal Campus three miles from the main campus, graduate student Daniel Sirbu is testing four-inch high models of occulters. The team collaborates closely with NASA’s Jet Propulsion Laboratory at the California Institute of Technology where an occulter is being built and tested with the help of engineers at Northrop Grumman and Lockheed Martin.

Video: How an occulter would unfold in space:

In addition to blocking light, Kasdin’s group is working to improve the technology for correcting faulty imaging caused by the Earth’s atmosphere, as well as heat, vibrations and imperfections in the telescopes themselves. All ground-based telescopes suffer from poor imaging quality due to atmospheric water vapor that is present even on cloudless nights, causing turbulence that makes stars appear to twinkle. Astronomers can correct these distortions using a technology known as adaptive optics which involves bendable mirrors. The Kasdin lab is working on improvements to these systems.

Coronagraphs and adaptive optics already are in use in a handful of telescopes, including the Subaru Telescope, operated by the National Astronomical Observatory of Japan (NAOJ), in Hawaii. Princeton researchers, including Kasdin and his colleagues, as well as Turner; astrophysical sciences professor Gillian Knapp; Timothy Brandt, a 2013 Ph.D. in astrophysical sciences; and others, are part of an international collaboration led by NAOJ scientist Motohide Tamura that is known as SEEDS (Strategic Explorations of Exoplanets and Disks with Subaru).

Kasdin’s group is working on designing an instrument, the Coronagraphic High Angular Resolution Imaging Spectrograph (CHARIS), to add to the Subaru Telescope to look at the different kinds of light, or spectra, emitted by a planet. Just as a prism splits white light into its rainbow of colors, CHARIS contains prisms and special filters that allow researchers to see the different wavelengths of light. These wavelengths provide signatures that can reveal the planet’s temperature and hint at which atoms and molecules are present around the planet. Graduate student Mary Anne Peters and Groff are working on CHARIS.

“The instrument makes it possible to look at the spectrum at each point in the image,” said Groff, “so you can distinguish the planet light from the star and see whether the planet’s atmosphere is uniform or cloudy, and you can get an idea of age because as the planet gets older, it cools.”

Beyond detection

Detecting exoplanets, whether by watching for their transits or by direct imaging, is just the first step in developing an understanding of these objects, said Adam Burrows, a professor of astrophysics who uses data gathered from these campaigns to construct theories about the characteristics of exoplanets and planetary systems. “Once we’ve detected planets, how do we figure out their makeup, their atmospheric compositions and temperatures, and their climates? These are the kinds of questions we are interested in answering,” Burrows said.

These questions can be addressed only by detecting and interpreting the spectral emissions that will be detected by instruments such as CHARIS, but so far these are only available for large exoplanets. “As larger ground-based telescopes and space-based missions like the James Webb Space Telescope come online,” Burrows said, “we will have data from planets that are closer in size to the Earth. The objects being studied now are but stepping stones toward the broader characterization of the planets in general in the galaxy and in the universe.”

This broader characterization includes ongoing studies by a number of other Princeton researchers, including Markus Janson, a NASA Hubble Postdoctoral Research Fellow in astrophysical sciences, who studies how planets are formed from dust and debris that orbits the star. Other researchers studying planet formation include Roman Rafikov, assistant professor in astrophysical sciences, and Ruobing Dong, who earned his Ph.D. in 2013 while working on the SEEDS project and is now a NASA fellow at the University of California-Berkeley. Emily Rauscher, a NASA Sagan Postdoctoral Fellow in astrophysical sciences, is studying the climate on these faraway worlds.

Many researchers hope that studying exoplanets will help us learn more not only about planetary formation and solar systems but also about whether other planets exist that could support life. The instruments and telescope networks being developed at Princeton could lead the way. And if a wild burro chews on a cable now and then, well, it is part of the cost of learning what lies outside our solar system.

Box: Data mining for planets

Xu (Chelsea) Huang

Xu (Chelsea) Huang (Photo by Keren Fedida)

Data mining for planets Xu (Chelsea) Huang remembers the thrill of finding her first planet. “It was exciting,” said the graduate student in astrophysical sciences. Huang found that planet and many more in 2012 while looking through a publicly available data set from NASA’s space-based Kepler mission, which scans for dips in starlight as the planet crosses in front of the star. Using techniques developed for analyzing HATNet findings under the guidance of Associate Research Scholar Joel Hartman and Assistant Professor Gáspár Bakos, Huang found 150 potential planets — many of which were hot “super-Earths” that are slightly large than Earth but orbiting their host stars much more closely — that the Kepler team and others had missed. The paper was published earlier this year in the journal Monthly Notices of the Royal Astronomy Society. When the Kepler mission later released an updated list of possible planets, about half the ones that Huang had found were on it.

Box: Forecasting the climate on other worlds

Emily Rauscher

Emily Rauscher, a NASA Sagan Postdoctoral Fellow at Princeton’s Department of Astrophysical Sciences, is modeling the climate on exoplanets. (Photo by Andrew Howard)

Emily Rauscher, a NASA Sagan Postdoctoral Fellow in the Department of Astrophysical Sciences, said that new acquaintances don’t believe her when she says she does climate modeling for exoplanets. Rauscher uses what is known about our solar system, plus the laws of fluid dynamics and the exoplanets’ orbital period and mass, to try to understand the climate on these faraway worlds. “If you watch a planet throughout its orbit, you can see the change in the amount of light emitted from the planet’s night side versus from its day side,” Rauscher said. “Because it is very hot in the day and very cold at night, we expect winds to blow around the planet, and by measuring the difference in brightness coming from the planet, we can detect how the wind affects the planet’s temperature.” Rauscher is fascinated by the idea of life on other planets but said that there is plenty to discover even on uninhabitable hot-Jupiters. “There is a big push to discover Earth-like planets,” she said, “but there is a lot we can learn from studying the planets we know about already.”

Box: Exploring how planets are formed

Studying exoplanets also could help researchers learn more about how planets are formed from dust and debris that orbits the star, said Markus Janson, a NASA Hubble Postdoctoral Research Fellow in the Department of Astrophysical Sciences. Some of the material that doesn’t end up in planets is collected in rings called debris disks, he explained. Our solar system has two such debris disks: an asteroid belt between Mars and Jupiter and the Kuiper Belt beyond Neptune.

“Our conventional theory of how planets form— that dust sticks together and forms into planets like Earth, and that sometimes large amounts of gas accumulate onto a rocky core to form gas giants like Jupiter — is based on what we’ve observed in our solar system.” Janson said. “Now we can study other solar systems, so we can test this theory.” A recent study by Janson and colleagues, accepted for publication by The Astrophysical Journal, indicates that the majority of exoplanetary systems probably did form in this manner.

-By Catherine Zandonella

Secrets of the Southern Ocean

southernocean

Marine geochemistry specialist Robert Key doesn’t consider himself particularly prone to depression. Yet emails to his wife from a research vessel on the freezing waters of the Southern Ocean depicted an emotional slump amid harsh conditions and brutal working hours.

“It’s wet and windy and miserable, and if you’re down there in the winter, then it’s dark the whole time as well,” said Key, a research oceanographer in the Program in Atmospheric and Oceanic Sciences. “You’re away from contact with people. Essentially all you do is eat and work.”

Robert Key

Robert Key collects water samples during a research voyage aboard the NOAA vessel, the Ronald H. Brown. (Photo courtesy of Robert Key)

But Key and other Princeton researchers push through the challenging conditions because they want to learn more about the waters at the bottom of the globe, which have a significant impact on the Earth’s ecosystems and climate. By collecting and analyzing samples of seawater, and using the results to help construct computer models of the ocean and atmosphere, the scientists aim to understand the Southern Ocean’s major influence on the world’s carbon and nutrient cycles. In doing so, they hope to provide insight into what our planet will look like in an era of human-driven climate change.

Though it makes up less than a third of the world’s ocean coverage, the Southern Ocean surrounding Antarctica soaks up about half of the man-made carbon dioxide absorbed by the world’s oceans from the atmosphere each year. Its waters act as a giant pump, with currents that carry carbon dioxide down into the deep recesses of the ocean where the carbon can remain for roughly 1,000 years. In return, currents bring up frigid water from the deep, water that has never been exposed to today’s elevated levels of carbon dioxide and therefore is able to absorb more of the gas than today’s surface waters.

Video

This frigid water also absorbs heat: the Southern Ocean has helped prevent the planet from warming up as much as it might have by now from human activity, according to Jorge Sarmiento, the George J. Magee Professor of Geoscience and Geological Engineering. Because its waters are so cold, the Southern Ocean absorbs about 60 percent of the excess heat that moves annually from the atmosphere into the ocean.

Along with absorbing carbon dioxide and heat, the Southern Ocean regulates the movement of nutrients such as nitrogen and phosphorus. The ocean’s patterns of circulation transport nutrient-rich water from the deep ocean back to the surface, where currents carry the nutrients to the north. These nutrients provide three-quarters of the ocean’s biological productivity, spurring the production of plant matter called phytoplankton that serves as the basis of the aquatic food chain.

Slideshow of the summer voyage of the research vessel R/V S.A. Agulhas II:

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“It’s old, it’s cold and it’s rich,” said Sarmiento. These traits, he explained, enable the Southern Ocean to have the influence that it does over global climate and nutrient regulation — and challenges scientists to find out how this massive storage vessel for carbon, nutrients and heat might react to rising carbon emissions and climate change.

Southern Ocean diagramA key question is whether rising carbon emissions will boost or hamper the Southern Ocean’s ability to sponge up carbon dioxide. Changing wind and rainfall patterns due to a warming Earth could shift how much carbon and heat the Southern Ocean can store in either direction, according to Daniel Sigman, the Dusenbury Professor of Geological and Geophysical Sciences. If winds pick up, for example, then mixing between the Southern Ocean’s deep and shallow waters may pick up as well. If high-latitude rainfall increases, more freshwater on the polar ocean’s surface may mean a higher density difference between the surface and deep waters, leading to less mixing. Depending on the response of ocean biology to this range of possible changes in ocean circulation, the rate of carbon uptake may either rise or fall.

Scientists have built models to predict how the Southern Ocean’s carbon sink will behave over the next several decades. But these researchers lack sufficient observations of the Southern Ocean to adequately inform high-resolution models of the ocean’s circulation, to assess the predictive powers of their models, or even to understand which processes are the most important for the models to provide accurate simulations. Data for winter at the Southern Ocean is especially sparse. A major reason: the brutal working conditions in the winter.

“I thought I knew something about winds and bad waters and blizzards and storms,” said climate modeler Joellen Russell, who grew up in an Eskimo village 31 miles above the Arctic Circle. “I couldn’t get my head around it.” Russell, an associate professor at the University of Arizona who collaborates with Sarmiento, remembers being thrown across her cabin one night when a wave slammed against the side of the ship, and how buckets of water would crash onto the deck in such great volume that the water looked black. “You’re like, ‘I want to go home now,’” she said.

Slideshow of the winter voyage of the research vessel R/V S.A. Agulhas II:

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Field research in the Southern Ocean, which typically lasts between 30 to 70 days, holds scientists to a punishing schedule. They can work up to 18 hours a day, seven days a week. Russell described a typical night working in a chemistry lab during one of her research cruises: she slept on a bean bag on the lab’s floor, waking up every 15 minutes to a beeping noise reminding her to perform certain laboratory tasks. The workhorse nature of the job stems mainly from the high cost of being out on the water: tens of thousands of dollars per day. “Because it’s so expensive to get out there, you feel the pressure,” Russell said. “You want every last bit of data you can get.”

On board the ship

Researchers aboard the National Oceanic and Atmospheric Administration (NOAA)’s ship, the Ronald H. Brown, performed experiments in the ship’s laboratory to analyze water samples for nutrient levels, alkalinity and other factors during this research cruise in March and April 2010. Clockwise from front left are: Benjamin Botwe, assistant lecturer at the University of Ghana; Charles Fischer, oceanographer at NOAA Atlantic Oceanographic and Meteorological Laboratory; Calvin Mordy, associate at NOAA Pacific Marine Environmental Laboratory; Yui Takeshita, graduate student at Scripps Institution of Oceanography; and Laura Fantozzi, staff research associate at Scripps Institution of Oceanography. (Photo by Ivy Frenger)

Fortunately, researchers now can use robotic battery-powered floats that provide salinity and temperature measurements for up to five years. About 3,500 of these floats, called Argo floats, are making measurements around the world’s seas. Funding and management for the floats come from the contributions of 23 countries.

But there are measurements that Argo floats leave out, and Associate Professor of Geosciences Frederik Simons hopes to fill in some of the gaps with an instrument of his own. Simons has spent the past few years developing an autonomous buoy, in collaboration with University of Rhode Island professor Harold Vincent, that detects GPS position, time and ocean depth while measuring seismic waves generated by distant earthquakes that are converted to water pressure waves at the ocean floor. They call their instrument the Son-O-Mermaid.
Simons hopes the Son-O-Mermaid will overcome the paucity of oceanic data, particularly in the Southern Ocean. “We are making pictures of the interior of the Earth using waves recorded through the Earth,” said Simons. “When we do that, we can learn about mantle plumes, subduction zones, mid-ocean ridge earthquakes — basic questions that people wonder about.”

Though the Son-O-Mermaid, which can stay in the water in a range of ocean conditions, is set up for use in seismology, researchers could easily adapt it for their own use in physical, chemical or biological data collection, according to Simons.

A three-decade legacy

Much of the groundwork for today’s understanding of the Southern Ocean comes from earlier work by Sarmiento, whose interest in the Earth’s carbon cycle began around 1984. This was when he co-wrote — with J. Robert Toggweiler, an oceanographer at the National Oceanic and Atmospheric Administration’s Geophysical Fluid Dynamics Laboratory in Princeton — one of the first papers to point out that the Southern Ocean’s waters dictate the carbon dioxide content of the atmosphere. His paper was one of three to become so influential in the field as to be given a nickname: the “Harvardton Bears” papers, so named because their authors were affiliated with Princeton, Harvard or the University of Bern.

Jorge Sarmiento

Professor Jorge Sarmiento (Photo by Denise Applewhite)

This early work revealed that the Southern Ocean acts as a leak in the ocean’s biological pump. The Southern Ocean actually releases some carbon dioxide into the atmosphere because phytoplankton, which consume carbon dioxide as they grow, cannot keep up with the rapid supply of nutrients and carbon from the underlying deep ocean and leave much of it unused.

Sarmiento has continued to investigate the ocean’s role in global climate over the three decades since, with a particular focus on the Southern Ocean. In 1996, he constructed a model that predicted how future global warming would affect the ocean’s ability to absorb carbon dioxide: he suggested that warming would weaken the ocean’s circulation, which would in turn compromise the movement of carbon dioxide to deep waters. His further research proposed new ideas about why atmospheric carbon dioxide was lower during ice ages, and he identified pathways that nutrients follow as they migrate from the Southern Ocean to seas farther north.

“You just fall into something, a fascinating problem that you can’t let go of,” said Sarmiento. “Suddenly things come together and you get an answer, and it’s different from anything that anyone else has come up with.”

Sarmiento, who began his Princeton career as the University’s only biogeochemist, is now surrounded by several colleagues examining the oceans’ biogeochemical processes: Michael Bender, professor of geosciences; François Morel, the Albert G. Blanke Jr. Professor of Geosciences; Stephen Pacala, the Frederick D. Petrie Professor in Ecology and Evolutionary Biology; and Bess Ward, the William J. Sinclair Professor of Geosciences.

Sarmiento also has good company in researchers such as Sigman, who has made major contributions to scientists’ knowledge about the Southern Ocean. Sigman is trying to understand the role of the Southern Ocean in global climate by studying past climate changes and reconstructing the strength of the carbon dioxide leak back through Earth history.

In particular, Sigman is exploring the hypothesis that the Southern Ocean carbon dioxide leak was reduced during the ice ages.

Daniel Sigman

Professor Daniel Sigman (Photo by Denise Applewhite)

Sigman uses marine sediments to identify how iron — which is carried to the Southern Ocean in dust originating in Africa, Australia and South America — has affected phytoplankton growth in the Southern Ocean and contributed to the global climate cycles of the Earth’s last 1 million years.

An essential nutrient for phytoplankton, iron is relatively scarce in the Southern Ocean. The lack of iron prevents phytoplankton populations from growing to numbers large enough for them to fully consume the ocean’s nutrients, including carbon dioxide. This means that a lot of carbon dioxide can leak right back into the atmosphere.

This may not have always been the case, however. By studying marine sediments, Sigman and his colleagues found evidence that more dust deposits in the past may have enabled phytoplankton in the subAntarctic zone — the Southern Ocean region roughly 40 to 50 degrees above the South Pole — to consume more carbon dioxide, which may have helped hold down the global temperature. That lower temperature would have caused stronger ice ages starting 1 million years ago, the scientists wrote in a 2011 paper published in Nature. With more dust — and thus more iron — in the water, phytoplankton growth escalated and ensured that excess carbon in the water was consumed before it escaped into the atmosphere as carbon dioxide gas. This allowed heat-trapping carbon dioxide to stay in the ocean.

“Our hypothesis is that iron supply to the sub- Antarctic zone is one of the two key ingredients that lowers atmospheric carbon dioxide during ice ages,” Sigman said.

The other ingredient is changes in the mixing of water between the surface and the deep ocean. With colleagues from the Swiss Federal Institute of Technology in Zurich, Sigman found evidence that the subAntarctic zone changes were complemented by circulation changes in the Antarctic zone, the Southern Ocean region adjacent to the Antarctic continent and south of the subAntarctic zone. At the beginning of each ice age of the last million years, the Antarctic zone appeared to reduce its vertical mixing, which may have slowed the leakage of carbon dioxide to the atmosphere and trapped more of it in the ocean, providing the first cooling step of the impending ice age. The cooling, in turn, encouraged more dust to be deposited in the ocean, in part because continents became drier and dustier. And the phytoplankton fertilized by this dust may then have caused further carbon dioxide drawdown and global cooling.

These two factors — more dust-borne iron and more mixing of waters — could have allowed the Southern Ocean to absorb more carbon dioxide in the past. These findings may hint at how the Southern Ocean will change as the Earth warms in the next few years, Sigman said, with the possibility of more mixing and less iron input.

With the Southern Ocean playing a considerable role in what the climate might look like in years to come, scientists such as Sarmiento see it as their responsibility to uncover knowledge that will enable others to understand the systems at work. But though Sarmiento and Princeton’s other Southern Ocean specialists have made considerable strides in investigating the ocean’s place in the global climate, challenges remain — from increasing public awareness of the Southern Ocean’s critical importance to uncovering cost-effective, automated methods of obtaining more data from this poorly sampled region.

Key especially looks forward to the latter: he hopes that new technologies will afford him a break from the rigors of Southern Ocean fieldwork.

“It gets harder and harder to work a 72-hour week,” he said. “You get too old to go out to sea as much as I used to.”

-By Tara Thean

Inventions Bridge the Gap between lab and marketplace

Road trip

A road trip offered Mark Zondlo and his team the opportunity to test their new air quality sensors. (Photo by Lei Tao)

The college experience often involves at least one road trip, but most students do not bring along their faculty adviser. But last spring, two graduate students crammed into a rented Chevy Impala with Professor Mark Zondlo and a postdoctoral researcher to drive eight hours a day across California’s Central Valley, testing their new air-quality sensors, which were strapped to a rooftop ski rack.

The sensors are an example of technologies being developed at Princeton that have the potential to improve quality of life as commercial products or services. Although teaching and research are Princeton’s core missions, the campus is home to a vibrant entrepreneurial spirit, one that can be found among faculty members who are making discoveries that could lead to better medicines as well as students working to turn a dorm-room dream into the next big startup.

“Princeton has a number of initiatives aimed at supporting innovation and technology transfer,” said John Ritter, director of Princeton’s Office of Technology Licensing, which works with University researchers to file invention disclosures and patent applications, and with businesses and investment capitalists to find partners for commercialization. “Our goal is to accelerate the transfer and development of Princeton’s basic research so that society can benefit from these innovations,” he said.

Crossing the valley

One of the ways that Princeton supports this transfer is with programs that help bridge the gap between research and commercialization, a gap that some call the Valley of Death because many promising technologies never make it to the product stage. One such program is the Intellectual Property Accelerator Fund, which provides financial resources for building a prototype or conducting additional testing with the goal of attracting corporate interest or investor financing.

Zondlo, an assistant professor of civil and environmental engineering, is one of the researchers using the fund to cross the valley — in this case literally as well as figuratively. Earlier this year, Zondlo and his research team, which consisted of graduate students Kang Sun and David Miller and postdoctoral researcher Lei Tao, tested their air-quality sensor in California’s Central Valley, a major agricultural center that is home to some of the worst air pollution in the nation.

Their goal was to compare the new portable sensors to existing stationary sensors as well as to measurements taken by plane and satellite as part of a larger NASA-funded air-quality monitoring project, DISCOVER-AQ.

One of the new sensors measures nitrous oxide, the worst greenhouse gas after carbon dioxide and methane. Nitrous oxide escapes into the air when fertilizers are spread on farm fields. Currently, to measure this gas, workers must collect samples of air in bottles and then take them to a lab for analysis using equipment the size of refrigerators.

Zondlo’s sensor, which is bundled with two others that measure ammonia and carbon monoxide, is portable and can be held in one hand, or strapped to a car roof. “The portability allows measurements to be taken quickly and frequently, which could greatly expand the understanding of how nitrous oxide and other gases are released and how their release can be controlled,” Zondlo said.

The sensors involve firing a type of battery-powered laser, called a quantum cascade laser, through a sample of air, while a detector measures the light absorption to deduce the amount of gas in the air. The researchers replaced bulky calibration equipment, necessary to ensure accurate measurements in the field, with a finger-sized chamber of reference gas against which the sensor’s accuracy can be routinely tested.

The decision to commercialize the sensor arose from the desire to make the device available to air-quality regulators and researchers, Zondlo said. “Our sensor has precision and stability similar to the best sensors on the market today, but at a fraction of the size and power requirements,” said Zondlo, a member of the Mid-Infrared Technologies for Health and the Environment (MIRTHE) center, a multi-institution center funded by the National Science Foundation (NSF) and headquartered at Princeton. “We are already getting phone calls from people who want to buy it.”

Lighting up the brain — with help from a synthetic liver

Far from the dusty farm roads of California, Princeton faculty member John (Jay) Groves sits in his office in the glass-enclosed Frick Chemistry Laboratory, thinking about the potential uses for a new synthetic enzyme. Modeled on an enzyme isolated from the liver, the synthetic version can carry out reactions that human chemists find difficult to pull off.

One of these reactions involves attaching radioactive fluorine tags to drugs to make them visible using a brain-imaging method known as positron emission tomography (PET) scanning.

PET scans of the radiolabeled drugs could help investigators track experimental medicines in the brain, to see if they are reaching their targets, and could aid in the development of drugs to treat disorders such as Alzheimer’s disease and stroke, according to Groves, Princeton’s Hugh Stott Taylor Chair of Chemistry. The synthetic enzyme adds fluorine tags without the toxic and corrosive agents used with radioactive fluorine today.

Groves’ initial work was supported by the NSF, but to develop the technology for use in pharmaceutical research, the Groves team, which includes graduate students Wei Liu and Xiongyi Huang, is receiving funding from a Princeton program aimed at supporting concepts that are risky but have potential for broad impact. The Eric and Wendy Schmidt Transformative Technology Fund was created with a $25 million endowment from Google executive chairman Eric Schmidt, a 1976 alumnus and former trustee, and his wife, Wendy.

“The Schmidt funding is enabling us to explore ways to optimize the chemical reaction and create a prototype of an automated system,” Groves said. “This will allow us to create a rapid and noninvasive way to evaluate drug candidates and observe important metabolites within the human brain.”

Aiding the search for planets

Tyler Groff

Postdoctoral researcher Tyler Groff is creating an improved system for adjusting the blurry images seen through telescopes due to atmospheric turbulence, heat and vibrations. (Photo by Denise Applewhite)

Inspired by the search for planets outside our solar system, Princeton postdoctoral researcher Tyler Groff conceived of a technology that could enhance the quality of images from telescopes. Groff received Schmidt funding to develop a device for controlling the mirrors that telescopes use to correct blurring and distortion caused by atmospheric turbulence, heat and vibrations.

This technology, known as adaptive optics, involves measuring disturbances in the light coming into the telescope and making small deformations to the surface of a mirror in precise ways to correct the image. These deformations are made using an array of mechanical devices, known as actuators, each capable of moving a small area of the flexible reflective surface up or down. But existing actuators are limited in the amount of correction they can provide, and the spaces between the actuators create dimples in the mirror, producing a visible pattern in the resulting images that astronomers call “quilting.”

Groff envisioned replacing the array of rigidly attached actuators with flexible ones made from packets containing iron particles suspended in a liquid, or ferrofluid. Just as iron filings can be moved by waving a magnet over them, applying varying magnetic fields to the ferrofluid changes the shape of the fluid in ways that deform the mirror.

The ferrofluid mirror enables highquality images while being more resistant to vibrations and potentially more power efficient, which will be important for future satellite-based telescopes, said Groff, who works in the laboratory of Jeremy Kasdin, professor of mechanical and aerospace engineering. A ferrofluid mirror can also achieve something that a rigid actuator mirror cannot: it can assume a concave or bowl-like shape that aids the focusing of the telescope on objects in space. “A telescope that uses ferrofluid mirrors would be able to see dim objects better,” Groff said, “which would greatly enhance our ability to probe other solar systems.”

From drug discovery to space exploration, Princeton’s dedication to supporting technology transfer and potentially disruptive but high-risk research ideas is yielding tremendous benefits for the advancement of science and the improvement of people’s lives.

Box: From student project to startup

Carlee Joe-Wong (Photo by Steve Schultz)

Carlee Joe-Wong (Photo by Steve Schultz)

In 2009 when Princeton undergraduate Carlee Joe-Wong started working on the technology that would become the DataMi company, she didn’t even own a smartphone. Today, the startup company co-founded by Joe-Wong provides mobile traffic management solutions to wireless Internet providers, and also helps consumers manage their data usage through an app, DataWiz, that has been downloaded by more than 200,000 Apple and Android users.

Joe-Wong became involved in the study of mobile data usage in the spring of her junior year when Professor Mung Chiang challenged her to explore ways that wireless providers could reduce congestion by adjusting their prices based on the variations in network supply and demand. “I mostly just worked on the project in my dorm room,” Joe-Wong said. “I thought it would be cool if it was adopted but I didn’t think that I would be the one helping to make that happen.” After graduation, Joe-Wong became a graduate student working with Chiang on mathematical algorithms that predict the most effective methods for balancing network use across “peak” minutes and “valley” minutes.

“With companies charging $10 per gigabyte, mobile consumers today need to intelligently manage their data,” said Chiang, the Arthur LeGrand Doty Professor of Electrical Engineering. “What the DataWiz app does is tell you when, where and what app used how much of your quota.”

In May 2013 the team, under the engineering leadership of associate research scholar Sangtae Ha, opened an office for DataMi one block off campus. Needless to say, Joe-Wong now has a smartphone.

Taking it to the streets with help from Princeton’s eLab

ELab students

From left: Nathan Haley, Christine Odabashian, Luke Amber and Leif Amber. (Photo by Denise Applewhite)

A love of motorcycles brought them together: three Princeton undergraduates decided to explore building and marketing an electric motorcycle to provide a superior riding experience at significantly lower emissions than gasoline powered models.

The team was one of nine groups selected to participate in the 10-week eLab Summer Accelerator Program, an initiative of the Keller Center in the School of Engineering and Applied Science, which teaches entrepreneurship by offering resources, mentoring and working space.

Throughout the summer, the team members worked on ways to market the bike while simultaneously building a prototype. “We geared the product toward people who enjoy taking weekend trips,” said Nathan Haley, Class of 2014, an economics major.

Haley was joined by Luke Amber, Class of 2015, and Christine Odabashian, Class of 2014, both majors in mechanical and aerospace engineering. The team also included Luke’s older brother, Leif Amber, a graduate student in electrical engineering at Clarkson University.

-By Catherine Zandonella

The Princeton Plasma Physics Laboratory: Blazing a path to fusion energy

Ask researchers at the U.S. Department of Energy’s Princeton Plasma Physics Laboratory (PPPL) to name one of the greatest science and engineering challenges ever undertaken and the answer comes easily: harnessing fusion energy.

Fusion happens naturally in the sun and other stars. The tremendous gravity from these massive stellar objects crushes together the nuclei of hydrogen atoms and releases vast amounts of energy. Bringing this process down to Earth could provide a safe, clean and virtually limitless supply of power for generating electricity.

But harnessing fusion energy is a supremely difficult task. The positively charged nuclei — or ions — inside atoms resist being squeezed together, and there is no solar gravity in laboratories to force the stubborn particles to merge.

Enter PPPL’s National Spherical Torus Experiment (NSTX-U). This device, called a “tokamak,” is in the midst of a $94 million upgrade that will make it the most powerful fusion facility of its kind in the world when the work is completed in 2014. Such facilities heat hydrogen to astronomical temperatures and trap it in magnetic fields to produce the superhot, electrically charged plasma gas that fuels fusion reactions.

Scientists then study the gas to learn how to use it to create a “burning plasma,” or sustained fusion reaction — the goal of global fusion research. “It’s as if we’re trying to create a state of matter on Earth that hasn’t existed before,” said PPPL Director Stewart Prager. “And that’s a hard thing to do.”

PPPL is a leader in this worldwide quest and a key source of public information and classroom instruction about the physics involved. The laboratory, which is managed by Princeton University and is located about three miles from campus, collaborates in major fusion experiments in Europe, Asia and the United States, and conducts educational programs for participants ranging from the general public to graduate students (see box and map).

The NSTX-U upgrade will enhance all capabilities of the machine. The temperature inside the three-story-tall tokamak could rise above 60 million degrees Celsius during experiments and reach six times the temperature at the core of the sun. The electric current that powers the machine’s huge magnets will double, as will the strength of the magnetic fields.

The sharply increased forces will quadruple the stress on all the NSTX-U components that support the magnets. This has required PPPL engineers to redesign and reinforce such structures throughout the machine. “It took a tremendous amount of analysis time to do this,” said engineer Ron Strykowsky, project manager for the upgrade.

Research on the powerful NSTX-U, whose spherical shape resembles a cored apple as compared with the donut-like shape of conventional tokamaks, will be followed by fusion researchers around the world. Experiments will show whether the streamlined, spherical design of the PPPL machine can serve as a model for the next major step in U.S. fusion research, and will produce vital data for ITER, the huge international fusion facility under construction in France.

PPPL has charted a five-year plan of action for the NSTX-U. The spherical device set records for efficient plasma confinement when it operated from 1999 to 2011 prior to the upgrade. Researchers now want to see if the enhanced machine can confine far hotter and harder-to-corral plasmas just as efficiently.

Plans also call for testing a system that will line the inner walls of the tokamak to protect them from the scorching plasma that escapes the magnetic field. Researchers will coat the walls with a thin layer of lithium, a silvery metal that turns liquid when struck by stray particles, to absorb the hot gas. “It works the way sweat moistens and protects the skin,” said Masayuki Ono, project director for the NSTX-U department at PPPL.

The escaping heat poses further challenges. The plasma could easily slice through a metal plate called a “divertor,” which serves as an exhaust system in tokamaks, unless the heat can be spread before it reaches the plate. Researchers will test an awardwinning device called a “snowflake divertor,” which PPPL helped develop and employed prior to the upgrade, to see how well it can spread the NSTX-U heat flux.

Likewise high on the PPPL agenda will be testing new ways to create and sustain the electric current that runs through tokamak plasmas. This current now is generated by a coil called a “solenoid” that will be unable to operate in the continuous fashion that future facilities will require. While the NSTX-U will still use a solenoid, researchers also will inject current through a pair of electrodes installed in the tokamak as a possible replacement for the coil.

Scientists will address all these issues in experiments called “shots” that will heat the plasma and run the NSTX-U magnets for up to five seconds — five times longer than previously possible. Preliminary plans call for some three shots an hour, eight hours a day, for 120 experiments a week.

These shots will determine if a spherically shaped tokamak could be a strong contender for the next key device in the U.S. fusion program. That envisioned device, called a Fusion Nuclear Science Facility (FNSF), would assemble and test all the components needed for a fusion power plant. This would pave the way for a demonstration fusion facility that would generate electricity on the grid and lead in turn to construction of a commercial fusion plant around the middle of the century.

The FNSF “would propel fusion forward fantastically,” said Prager. And the NSTX-U “will give us the physics information so the world can make a yes-or-no judgment about whether the spherical tokamak is a good candidate for that next step.”

Bringing plasma to the people

Plasma is everywhere, from the gas in neon light bulbs to the fuel that lights the stars. PPPL’s mission includes highlighting the properties of this fourth state of matter for the general public and inspiring and educating the next generation of scientists. “We want the public to know what we do and why we do it,” said John DeLooper, head of the best practices and outreach programs at PPPL. “And we want to excite young people to go into the world of science.”

The Princeton Plasma Physics LaboratoryThe laboratory carries out this role through wide-ranging programs. PPPL has a variety of portable scientific demonstrations and experiments that staffers bring to public events and school classrooms. The laboratory also provides a 10-week summer internship in plasma physics for college undergraduates. Seventy-two percent of the physics and engineering students who have taken the course have entered doctoral programs in physics since 2000.

For students who go on with their studies, PPPL supports graduate education chiefly through the University’s Program in Plasma Physics in the Department of Astrophysical Sciences. The program has awarded more than 265 doctorate degrees, many to people who have become leaders in the field.

-By John Greenwald

Activism Shapes Africa Scholar

Leonard Wantchekon

Princeton Professor of Politics Leonard Wantchekon has built upon his past as a political activist in the West African nation of Benin to forge an academic career focused on studying — and working to shape — governance and institutions in Africa. (Photo by Denise Applewhite)

Leonard Wantchekon’s education began  as a young child in his home village of Zagnanado, in the West African nation of Benin, where elementary school classes gave way to long soccer games and evenings of storytelling by aunts and uncles whose tales became informal history courses.

He left village life behind in a search for academic success that took him to the nation’s most populous city, Cotonou, to the National University of Benin to study mathematics, and eventually to North America and Princeton.

During his student years in Benin, Wantchekon became a pro-democracy activist. Planning meetings became his classes, fellow activists his classmates and acts of protest his final exams. Through the 1970s and ’80s he rose to a prominent place in the opposition that helped hasten the end of the oppressive regime of Mathieu Kérékou.

“All the time I tried to be two different persons in one,” Wantchekon said. “On the one hand I wanted to be the next big thing in academics in Africa. I wanted to be a top mathematician and was very ambitious, driven and enthusiastic. … At the same time, I was an equally ambitious pro-democracy activist. I was at the center of a social movement that was pushing for major political reforms in Benin.”

His twin paths of academic study and political activism frequently diverged and intersected until a morning in December 1986, when he escaped across the border into Nigeria following 18 months of incarceration as a political prisoner and three months on the run from authorities.

“It was — or rather, I was determined to make this — the dividing line between my past and my future,” Wantchekon wrote about that moment in his autobiography Rêver à contre-courant (Dreaming Against the Grain), published in French by L’Harmattan in 2012.

A quarter-century after leaving his home country, Wantchekon has built upon his remarkable past to forge an academic career focused on studying — and working to shape — governance and institutions in Africa.

He has emerged as one of the rare political scientists who works directly with politicians, using their campaigns as laboratories to study how best to engage voters on policies. He also studies how the benefits of education spread through a society, using his home village as one of the study sites. And he’s hard at work on his most ambitious project, establishing a graduate school and center for social science research in Benin.

“We shouldn’t underestimate how crucial it is that ideas that will help Africa develop have to come mostly from Africa and have to involve more Africans,” said Wantchekon, who joined the Princeton faculty in 2011 as a professor of politics and associate faculty member in the economics department. “This, of course, cannot happen overnight. So we need to set up great institutions of higher education with the hope that, over time, we develop enough talent to make a difference.”

Political campaign as laboratory

In Benin, Wantchekon is experimenting with ways to engage voters using the nation itself as a laboratory. “As a researcher and someone who has political experience, I’m interested in the following question: How can a candidate best communicate a policy platform to the electorate that is both good for the country and can help the candidate win?” Wantchekon said.

Town hall meeting

In his research on engaging voters, Wantchekon compared the effectiveness of two campaign strategies, a town-hall meeting versus a large campaign rally. He found that the town-hall meeting is more effective at getting people to vote for the candidate, and it was far more cost effective. (Photo courtesy of the Institute for Empirical Research in Political Economy, Benin)

With the cooperation of the candidates and funding from the International Development Research Council of Canada (IDRC), he is evaluating the effectiveness of two campaign techniques: town-hall meetings focused on issues versus the usual large and costly rallies that emphasize financial incentives for voters.

Wantchekon found that town-hall meetings are more effective than rallies both in terms of getting people to turn out to vote and getting them to vote for the candidate. “Not only are the people more informed,” he said, “but those who attend share what they have learned with others.” Some of the project results were published in the October 2013 issue of the American Economic Journal: Applied Economics. He completed a similar experiment in the Philippines earlier this year with support from Princeton’s Mamdouha S. Bobst Center for Peace and Justice, and is awaiting the results.

His next project is to explore the conditions under which holding primary elections within political parties, as is done in the United States, could encourage candidates to develop more thorough expertise on policy areas. “Competition between two candidates from the same party, running on the same platform, I think will encourage candidates to go deeper into the issues with the voters,” Wantchekon said.

Peter Buisseret, a Ph.D. student studying comparative politics, is collaborating with Wantchekon on this work. “Leonard is enormously enthusiastic about the projects we work on together, and also my own work,” Buisseret said. “As a co-author, he is truly collaborative: I feel very much an equal in the projects we work on, but at the same time I recognize how much intellectual and professional benefit I get from working with someone with his experience and knowledge.”

Wantchekon said his experience in graduate school shapes the way he relates to students. After fleeing Benin, he found his way to Canada, where he earned master’s degrees in economics from Laval University and the University of British Columbia.

In 1992, he went to Northwestern University, where he earned his doctorate in economics. But the transition to the American academic system — and an environment where only English was spoken — was difficult. He overcame the challenges, though, and secured a position as an assistant professor of political science at Yale University and later on the faculty of New York University.

Far-reaching benefits of education

Wantchekon’s experiences spurred him to explore how education has benefited people within villages and across generations in Benin, a country that experienced Western colonization. When Benin, then known as Dahomey, was colonized in 1895 by France, Catholic missionaries began setting up schools throughout the region. The missionaries’ goal was religious conversion, Wantchekon said, while the colonial government aimed to train local people to work as translators, nurses, accountants and security guards.

Colonial school 1936

Wantchekon studies the benefits of education on the income levels of descendants of the first students of missionary schools in Benin. One such school shown above in 1936 operated in Wantchekon’s home village, Zagnanado. (Copyright African Missions)

Using colonial archives, school rosters and oral histories, and with financial support from IDRC, Wantchekon identified 240 of the first students to attend school in the early 1900s at four sites in Benin. He noted that these students were not smarter or wealthier than the average Benin child but merely were fortunate to live near a school, so they can be thought of as randomly selected and representative of the population. He compared each group of 60 students to a representative sample of children from a village that lacked a school.

He found that the educated individuals experienced better incomes and living conditions. For example, only 14 percent of the educated students become farmers, whereas farming was the primary occupation among the uneducated (about 80 percent). He also found that the educated were more likely to have electricity and running water in their homes and to own a bicycle, motorcycle or car.

Wantchekon also found lasting effects that went beyond the individuals who received education. The children of the first students exhibited better outcomes, as might be expected, but what is particularly striking, Wantchekon said, is that the children of uneducated parents living in villages with schools did markedly better than descendants of uneducated parents in villages without schools.

“What I draw from this is the importance of aspiration,” he said. “When you see someone who makes it, he or she is your reference point, and you want to make it too. This is a very important finding for education policy. It is how you use the success of a few to encourage the success of many.”

Wantchekon said his findings resonate with his own experience. His mother, who was mostly uneducated, would show him pictures of his successful and educated uncle and urge her children to be like him. Of the children he went to school with in the village of Zagnanado, 10 others have earned Ph.D.s. “Entire villages in Benin have been completely transformed by education,” he said.

With a small team of students sponsored by Princeton’s Health Grand Challenge program, Wantchekon is now exploring whether the beneficial effects of education have continued to spread to the grandchildren of Benin’s first students in an era of increased competition for jobs.

Returning to Benin

Wantchekon isn’t just studying Africa’s past and present. He’s working to shape its future as founder of the African School of Economics (ASE), which is set to open in Benin in fall 2014. The goal of the ASE, Wantchekon said, is to create a center of excellence for social science research in Africa.

African School of Economics

Wantchekon is working to establish the African School of Economics (ASE), whose offices and a related organization, the Institute for Empirical Research in Political Economy, are currently housed in the building (top) in Abomey Calavi, Benin. Plans for a new ASE campus, pictured in the architectural renderings (bottom), are underway. (Photo courtesy of Serge Boya; architectural renderings courtesy of ASE)

The school, which has its roots in a research institute Wantchekon established in Benin in 2004, has received funding from the Women for Africa Foundation and SES, a satellite company based in Luxembourg, and is scheduled to open with about 300 master’s degree students.

“I’ve always thought that the way to promote social science research in Africa is to have a better African representation in social science research

in Africa,” Wantchekon said. “We need to solve development problems on the continent through original thinking and indigenous generation of knowledge.”

The ASE will bring together students and faculty from Africa and beyond with an academic focus on informing social science within the context and history of Africa. Classes will be taught in English. The school’s structure and curriculum have been established. The design of the school, to be based near the city of Cotonou, is nearing completion.

The ASE is also pursuing academic partnerships with universities around the world that he hopes will lead to a free flow of students, faculty and ideas. Earlier this year, Princeton announced a partnership involving Wantchekon and the University of São Paulo, the Center for Teaching and Research in Economics in Mexico, and the Institute for Empirical Research in Political Economy in Benin. As part of this program, ASE hosted a summer school and conference involving 12 graduate students from Princeton and 10 from African universities.

“One of the things the University is very excited about in terms of this initiative is the opportunity our faculty will have to collaborate with scholars in Western Africa and possibly in other countries in sub-Saharan Africa later,” said Diana Davies, vice provost for international initiatives. “Also, this allows us to engage in the activity of capacity building and helping to build up the next generation of scholars in Africa, which is something that’s very important to us.”

“Africa is part of the University’s larger internationalization effort,” said Jeremy Adelman, Princeton’s Walter Samuel Carpenter III Professor in Spanish Civilization and Culture, professor of history and director of the University’s Council for International Teaching and Research. “But the strategy has to be adapted to Africa. Figuring out how it’s going to work in Africa requires working with Africans.”

Wantchekon knows that much work remains to reach his goals for the ASE. “I am really determined to get there,” he said. “ASE enables me to nourish big ambitions and dreams for Africa while being among the best academics in America.”

By Michael Hotchkiss