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.


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

Telescopes take the universe’s temperature

Two telescope projects are measuring cosmic microwave background radiation with the goal of understanding more about the universe’s early history. The telescopes (pictured) are located on a peak in the Atacama Desert in Chile. (Image courtesy of ACT Collaboration)

Two telescope projects are measuring cosmic microwave background radiation with the goal of understanding more about the universe’s early history. The telescopes (pictured) are located on a peak in the Atacama Desert in Chile. (Image courtesy of ACT Collaboration)

Two telescopes on a Chilean mountaintop are poised to tell us much about the universe in its infancy. They are surveying the faint temperature fluctuations left over from the explosive birth of the universe, with the goal of piecing together its early history and understanding how clusters of galaxies evolved.

The telescopes are measuring these temperature fluctuations, known as cosmic microwave background radiation or CMB for short, from their perch 17,000 feet above sea level in Chile’s desolate Atacama Desert, where a dry atmosphere permits radiation to reach Earth with relatively little attenuation. In contrast to backyard telescopes that help us see visible light from stars and planets, these telescopes collect invisible microwave radiation.

Lyman Page

Lyman Page

These invisible waves are mostly uniform but contain slight differences in intensity and polarization that hold a wealth of information for cosmologists, said Lyman Page, the Henry De Wolf Smyth Professor of Physics. Page and Professor of Physics Suzanne Staggs co-lead two telescope projects, the Atacama Cosmology Telescope (ACT) and the Atacama B-mode Search telescope (ABS), which are funded by the National Science Foundation.

“If you imagine the temperature perturbations as a distant mountain range, the peaks and valleys correspond to the temperature variations,” Page said. “By looking at the patterns — the spacing between peaks, and whether they are narrow or fat — we are able to answer questions about the composition and evolution of the universe,” Page said.

ACT, which is about 18 feet across and looks like a giant metal bowl, has already made new discoveries, and confirmed and extended the findings of other CMB surveys, including two space-based telescopes, NASA’s Wilkinson Microwave Anisotropy Probe (WMAP) and the European Space Agency’s Planck mission. A new, more sensitive receiver is currently being mounted on the ACT telescope, which is a collaborative effort with David Spergel, Princeton’s Charles A. Young Professor of Astronomy on the Class of 1897 Foundation, along with researchers at the University of Pennsylvania, National Institutes of Standards and Technology, the University of British Columbia, and 10 other institutions contributing significantly to the instruments and analysis.

Suzanne Staggs

Suzanne Staggs

The CMB originated in the hot plasma soon after the Big Bang, which cosmologists consider to be the birth of the universe. As the universe expanded, the radiation propagated, carrying the secrets of the early universe with it. One of the questions is why the CMB on opposite sides of the universe is so similar in temperature. The leading explanation of this observation is the inflation model, which posits that the universe underwent a rapid acceleration of its expansion just after the Big Bang.

This is where the lower-resolution, second telescope comes in. Co-led by Staggs, the ABS is looking for signs of inflation. “Inflation should produce gravitational waves which create patterns in the CMB called ‘B modes,’” said Staggs. B modes are extremely faint — to measure them requires an instrument that can detect temperature changes of just billionths of a degree. To obtain these sensitivities, ABS mirrors, which are relatively small at about two feet across, sit inside a cryogenically cooled barrel.

The two telescopes can be operated remotely, but require frequent trips to the Chilean peak, which often include Princeton students and postdocs. The team at Princeton includes Senior Research Physicist Norm Jarosik, Associate Research Scholar Jonathan Sievers, postdoctoral researchers Matthew Hasselfield, Rénee Hložek, Akito Kusaka and Laura Newburgh, and graduate students Farzan Beroz, Kang Hoon (Steve) Choi, Emily Grace, Colin Hill, Shuay-Pwu (Patty) Ho, Christine Pappas, Lucas Parker, Blake Sherwin, Sara Simon, Katerina Visnjic and Sophie Zhang.

–By Catherine Zandonella

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

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

The social network: Program combats bullying

New laws and policies to address harassment and intimidation in schools are sprouting up in every state. But can laws and polices put a stop to bullying, or do students play a role?

Psychologist Elizabeth Levy Paluck has set out to demonstrate that students can change the climate of a school from one that tolerates bullying to one that promotes positive behavior. She is leading a research program in 58 New Jersey middle schools that harnesses the power of students’ social networks to change behavior and reduce bullying.

Elizabeth Paluck

Elizabeth Levy Paluck, an assistant professor of psychology and public affairs, is pursuing research in New Jersey middle schools to test whether it is possible to change social norms regarding bullying by targeting students’ social networks. (Photo by Denise Applewhite)

The project tests the premise that the best way to change social norms is to target the most socially connected people, and then allow the change to diffuse through the group, said Paluck, an assistant professor of psychology and public affairs. “People construct their ideas of acceptable behavior by observing others, especially influential individuals,” she said. “We would like to know if we can change the culture of a school by first changing the attitudes and behavior of these individuals.”

Paluck stressed that while some of these students are “popular,” others are the unofficial leaders of non-mainstream social groups organized around a common interest such as skateboarding or glee club.

Paluck is conducting the project, which is supported by the William T. Grant Foundation, the Spencer Foundation, the Canadian Institute for Advanced Research and Princeton’s Educational Research Section, with Hana Shepherd, a postdoctoral research associate in the psychology department and Princeton’s Woodrow Wilson School of Public and International Affairs.

The first step in the project, which began in fall 2012, was to identify a school’s influential students, or “social referents.” The researchers asked the entire student body to fill out a questionnaire listing the other individuals in his or her network. Privacy was preserved via use of anonymous codes. Using a mathematical algorithm, the Paluck team then constructed models of every social network in the school and combed for individuals with lots of connections within networks.

Social network

Elizabeth Levy Paluck, assistant professor of psychology and public affairs, and her team mapped the social networks of middle school students to identify influential individuals (social referents), who were then randomly assigned to either participate or not participate in an intervention program designed to reduce conflict in schools. In a pilot study, the researchers found that students (first-degree and second-degree connections) in the networks of social referents who participated in the antibullying program were less likely to view conflict as acceptable at the school, and were less likely to be disciplined for peer conflict, compared to students in networks of social referents who did not participate in the intervention program. (Original illustration courtesy of Elizabeth Levy Paluck.)

Once identified, some of these well connected individuals were randomly selected to join a group where they learned about bullying prevention and created an intervention program to spread positive social norms through efforts such as student assemblies, posters and wristbands. “It was important that the students design the program, to ensure that it meets their needs,” Paluck said.

Prior to starting the intervention program, the researchers conducted a baseline survey of attitudes toward bullying. At the end of the 2012-13 school year, the team conducted a follow-up survey of attitudes and collected information on behaviors. While the New Jersey results are not yet in, a pilot project in a school in Connecticut found improvements in attitudes about bullying and in reduced incidents of harassment and intimidation.

The much larger New Jersey study should allow the researchers to compare schools that received the intervention to those that did not. Within each school, the researchers can compare the attitudes and behaviors of students who belong to the networks of socially influential students who participated in creating antibullying interventions to students in the networks of influential students who did not participate.

“We need to know whether we changed the climate of conflict, did we set into motion a new expectation of what behaviors are desirable, did we make an overall difference?” Paluck said. “You cannot test this with only one social network, you have to compare to other networks where intervention was not done.”

–By Catherine Zandonella

Far from random, evolution follows a predictable pattern

Large milkweed bugs

Large milkweed bugs (above) feed on plants that produce a class of steroid-like cardiotoxins called cardenolides as a natural defense. The ability to eat these plants has evolved separately but in a predictable manner in several different orders of insects, including butterflies and moths (Lepidoptera); beetles and weevils (Coleoptera); and aphids, bed bugs, milkweed bugs and other sucking insects (Hemiptera). (Photo courtesy of Peter Andolfatto)

Evolution, often perceived as a series of random changes, might in fact be driven by a simple and repeated genetic solution to an environmental pressure, according to new research.

“Is evolution predictable? To a surprising extent the answer is yes,” according to Peter Andolfatto, an assistant professor in Princeton’s Department of Ecology and Evolutionary Biology and the Lewis-Sigler Institute for Integrative Genomics.

Andolfatto’s team has found that knowing how external conditions affect the proteins encoded by a species’ genes could allow researchers to determine a predictable evolutionary pattern driven by outside factors. Scientists could then pinpoint how the diversity of adaptations seen in the natural world developed even in distantly related animals.

The researchers carried out a survey of DNA sequences from 29 distantly related insect species, the largest sample of organisms yet examined for a single evolutionary trait. Fourteen of these species have evolved a nearly identical characteristic due to one external influence — they feed on plants that produce cardenolides, a class of steroid-like cardiotoxins that are a natural defense for plants such as milkweed and dogbane.

Though separated by 300 million years of evolution, these diverse insects — which include beetles, butterflies and aphids — experienced changes to a key protein called sodium-potassium adenosine triphosphatase, or the sodium-potassium pump, which regulates a cell’s crucial sodium-to-potassium ratio.

The protein in these insects eventually evolved a resistance to cardenolides, which usually cripple the protein’s ability to “pump” potassium into cells and excess sodium out.

To make this discovery, Andolfatto and his co-authors first sequenced and assembled all the expressed genes in the studied species. They used these sequences to predict how the sodium-potassium pump would be encoded in each of the species’ genes based on cardenolide exposure.

The researchers found that the genes of cardenolide-resistant insects incorporated various mutations that allowed them to resist the toxin. During the evolutionary timeframe examined, the sodium-potassium pump of insects feeding on dogbane and milkweed underwent 33 mutations at sites known to affect sensitivity to cardenolides. These mutations often involved similar or identical amino-acid changes that reduced susceptibility to the toxin. On the other hand, the sodium-potassium pump mutated just once in insects that do not feed on these plants.

Jianzhi Zhang, a University of Michigan professor of ecology and evolutionary biology, said that the Princeton-based study shows that certain traits have a limited number of molecular mechanisms, and that numerous, distinct species can share the few mechanisms there are. “The finding of parallel evolution in not two, but numerous herbivorous insects increases the significance of the study because such frequent parallelism is extremely unlikely to have happened simply by chance,” said Zhang, who is familiar with the study but had no role in it.

Andolfatto worked with lead author and Postdoctoral Research Associate Ying Zhen, and graduate students Matthew Aardema and Molly Schumer, all from Princeton’s ecology and evolutionary biology department, as well as Edgar Medina, a biological sciences graduate student at the University of the Andes in Colombia. The research was supported by grants from the Centre for Genetic Engineering and Biotechnology, the National Science Foundation and the National Institutes of Health and was published in the Sept. 28, 2012, issue of Science.
–By Morgan Kelly