Spring 2013

princeton journal of science and technology

Featuring:

$200

$150

$100

$250mil

$250 mil

No. 2013

Stopper Sequester

sequester

What does it mean for Princeton science?

the seQUester

snapshots oF science

Worms & mind control

organs in a petri dish

university president

shirley tilghman

inside:

2

biologyhealthengineeringphysics + math

Editor-in-ChiefStephen Cognetta

Lead DesignerEugene Lee

Business ManagerChristine Chien

WebmasterLucas Ho

EditorsMatthew BlackburnAbrar ChoudhuryJames EvansNassim FedelKristen Houston

Samuel KimShreya NathanTayyab ShahHelen YaoEddie Zhou

Senior WritersStacey HuangJulia Metzger

Kiran VodrahalliMichael Zhang

WritersSamuel ChangCissy ChenEli ChertkovEvan ChowSwetha DoppalapudiMizzi GomesSarthak GuptaDavid HarrisSahana JayaramanAlexandra JunnSydney KerstenGwen LeeRachel LeizmanMattie Lloyd

Bennett McIntoshNeil MehtaChelsea ParkerFred ShaykisGreta ShumGina SunEugene TangMeredith WrightJenny WuEd XiaoElizabeth YangKevin ZhangJen ZhaoKarena Cai [business]

DesignersJessie Liu [senior]Angela Zhou [web]Rory Fitzpatrick

Neeta PatelErica TsaiJessica Vo

Featured IntervieweesChristopher Tully (PHY) Gaspar Bakos (AST) Bernard Chazelle (COS) President Shirley Tilghman Mark Rose (MOL) Sam Wang (MOL) Celeste Nelson (CBE) DataMi Research Team Arvind Narayanan (COS) Thomas Gregor (PHY) Zemer Gitai (MOL) Andrew Leifer (Lewis-Sigler)

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What is Innovation?Innovation Journal is a student run publication that highlights Princeton’s science news.

Free copies can be found at at Frist Campus Center, the E-Quad, and various other locations on campus. Innovation is published once a semester.

Contact innov@princeton.edu for interest in making donations or joining our staff.

STAFF

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TABLE OF CONTENTS

18 20 22

10

HATNet

Internet Privacy

Ptolemy Natural Algorithms

Digital Identities

The search for the oldest relic of the universe extrasolar planets

PHYSICS + MATH

ENGINEERING

6

161412

TUBE

Molding Organs

FEATURE

Snapshots of Science

Time Dependent Pricing

Featuring Guest Photographers

in Drosophila MelanogasterPrinceton Science and the Sequester

Studying brain behavior in C. elegans

HEALTH

BIOLOGY

8

4innovation

SymmetryOptogenetics

Germany’s city of Duisburg is the largest steel-producing city. This is a photo of Duisburg’s €2 million “Tiger and Turtle” walking roller coaster sculpture. It’s a roller coaster that humans “ride” at their own, walking pace. At night, it is lit up for tourists and city-goers. The wind blowing at my face from the height this photo was taken, in combination with the way it looks like a “stairway to heaven,” was breathtaking.by Kyle Douglas ‘15

SNAPSHOTS OF SCIENCElayout by Rory Fitzpatrickselections by Nassim Fedel and Kiran Vodrahalli

1

43

2

The demonstrator in Freshman Seminar “Chemistry of Magic” who appears to be breathing fire is actually holding a straw filled with cornstarch. When he blows the corn starch out over the Bunsen burner flame, the particles catch on fire and create a giant fire ball. by Maylin Meisenheimer ‘16

1

4

3

2

A Princeton Communiversity visitor is watching a physics demonstration. Students explained the transference of potential energy to kinetic energy, and visitors were able to practice the lesson they learned by increasing the electric charge within a closed box. by Irene Burke ‘16

Students’ movements on the dance floor are captured using extended shutter release photography and ex-clusion blending of multiple photographic layers at the MIMA: Substance event in the Architecture building. by Luke Cheng ‘14

A gear from a magnetic motion machine model demonstrating the unique orientation of magnets within a rotor. built and photographed by Samuel Chang ‘16

Two QuesTions in ReveRse engineeRing oRgan DevelopmenT

Question 1:What cellular environment trig-gers organ growth?

Question 2:What shape do organs grow in?

Extracellular fluid surrounds cells, and is im-portant for the transportation of organic ma-terials necessary to maintain cellular structure and function.

However, the specific environment around cells necessary to trigger the formation of tissues is still unknown

begin with differently shaped hydrogels

place cells intosymmetrical and

Y-shaped hydrogel

It was found that cells grow better in

Y-shaped (asymmetrical)

hydrogels

IngredIents: EnzymEs, salts, sugars, protEins, stEm cElls

Different concentrations of ingredients change the chemical properties of the cellular environment. Certain properties signal cells to replicate and organize into a certain shape.

organic materials

extracellularFluid

cell

7

health

In the human body, cells are surrounded by extracellular fluid. This fluid is mostly water but contains many ions, enzymes, sugars, salts, and other proteins. All of the chemicals in this fluid are important for the transportation of organic materials nec-essary to maintain cellular structure and function – whether it is to repair the cell, remove waste from the cell, or communi-cate between cells. When tissues start as a few cells, the environment around these few cells, such as the extracellular fluid, contains specific chemical properties in or-der to signal that the cells need to replicate and become organized into a certain shape to form a tissue, and eventually an organ. However, the specific environment around cells necessary to trigger the formation of tissues is still unknown. In order to study possible environments necessary for the formation of tissues, Professor Nelson used structures known as hydrogels.

Hydrogels are hydrophilic (water-stabi-lized) polymers and therefore very water absorbent. The hydrogels can be molded into specific shapes and can have specific chemical, mechanical, and physical proper-ties that cells need to replicate and develop. Hydrogels can also be placed in water with certain chemicals to mimic the extracel-lular environment of cells starting to form tissues. Therefore Professor Nelson is changing the shape and properties of hy-drogels and the environment the hydrogel is in, to determine the signals that trigger the development of specific organs. She

used polymers to create molds of different shapes that became the shapes of the hy-drogels, and then placed some cells in the hydrogels. The shape of the hydrogel that allowed for the most cell growth suggested that it was a similar shape to how organs develop in organisms.

Professor Nelson started with the shapes that are similar to those found in the early development of living organisms. These were all molds that had symmetry, such as spheres, squares, an upside-down Y, and small tree like shapes. What Professor Nelson found was that the molds that had less symmetry, such as an upside-down Y and small tree like shapes, were molds that caused the most cell growth. In fact, the molds of an upside-down Y, or a similar tree-like mold is the shape that every or-gan originates from. All the molds that Pro-fessor Nelson tried did cause cell growth, however the cell growth in the more sym-metric molds, such as spheres, was not like in vivo growth.

As Professor Nelson continues the re-search, she is looking to use slightly more complex structures for her hydrogel model and mimic the in vitro conditions to what takes place in chicken and mice embryos, which are common organism models for this field of research.

While the research is still in its early stages, and is far from being ready to have clinical applications, which would be at least 20 or 30 years down the line, the infor-mation that Professor Nelson is gathering

about the conditions necessary for the start of organ development is promising. She says, “If you really understand what is go-ing on [with organ development] you should be able to recapitulate it ex vivo (outside the body).” Her research could eventually lead to growing an organ outside of a human body which would help organ transplants, and could be used as systems to test out therapeutic treatments for congenital dis-eases. Professor Nelson says, “[For] con-genital diseases that have no treatments right now, we know the causes, but there’s a hole as to why the cells in those diseases develop the way they do. If we can gain any bit of insight as to how these diseases de-velop, it’s helpful to find therapeutic tar-gets,” for those diseases. If organs can be created outside the body, they can also help avoid ethical concerns. Currently the main way to study living organs would be to do testing on humans and fetuses, however, if living organs can be developed outside the body, studies can be done using those or-gans instead.

While Professor Nelson became inter-ested in this research because of its poten-tial applications, she is also interested in this research because “Organs are beau-tiful, but what we can build outside of the body right now looks like a tumor, which it should not be.” By studying how organs develop in their earliest stages, Professor Nelson’s research could help scientists with the groundbreaking tool and resource of molding tissue into functional organs.

molDing oRgans

by Sahana Jayaraman, interviewing Professor Celeste Nelson (CBE) designed by Eugene Lee and Jessica Vo

The First steps of Development

Could organs be developed outside the body? Professor Nelson, in the Chemical and Bi-

ological Engineering department, is looking into this very question. Starting out as a few

progenitor stem cells, organs develop into complex yet organized structures. But what

continues to fascinate and baffle scientists is how organs are able to develop – what are

the processes that occur to turn these few cells into a complex structure that carries out

vital chemical and biological processes?

8

engineering

TUBE: Time-dependent PricingBy Stacey Huang interviewing the DataMi research team

Designed by Jessie Liu

Treating the sickness of network congestion through smart pricing for mobile data

Most of us have been a victim of congested networks at one point or another, often far more often than we’d like. From that cat video that just doesn’t load on YouTube to the intransigent SCORE website during course registration, slow networks can be a never-ending source of frustration. Yet, away from the boons of student life and free internet, congested networks are more than an annoyance: they also mean a higher bill, and the prices are only getting higher. As consumer data consumption doubles every year and bandwidth-hungry devices proliferate in the market, it has become increasingly difficult for Internet Service Providers (ISPs) such as AT&T and Verizon to provide data at a reasonable price while satisfying the high demands of users. Cur-rent technology simply cannot keep up with the level of user demand.

Since 2009, a Princeton research team has been working to combat this problem. Working in EDGE, Professor Mung Chiang’s own Princeton networking lab, the team, which is led by Associate Research Scholar Sangtae Ha, takes an innovative approach that involves not only improving existing technology but also working to maximize economic factors. “The solution requires mechanisms beyond technology, such as economics, as ways to address the problem

of growing congestion. It is a natural way to address this issue to obtain a win-win across consumers and internet service pro-viders and benefits everyone,” described Dr. Soumya Sen, a postdoc research asso-ciate involved in the project. The elegant solution? “TUBE,” or “Time-dependent Us-age-based Broadband price Engineering,” which allows users to pay different prices depending not only on how much data they transfer across the Internet but also on when they access it. Simply put, users re-ceive discounts for deflecting usage, such as downloading and streaming, to when the network is less busy. A test trial of 50 people at Princeton yielded positive results, and the team is now moving to implement the technology on a larger scale.

The Battle with Network CongestionThe system of dynamic prices is nothing

new; data pricing structures were incorpo-rated in voice call pricing far before the era of internet. The research team has been working to implement a more nuanced version of this idea for mobile data, which unsurprisingly is the sector which has seen the greatest rise in demand within the past few years.

The key with time-dependent pricing is adapting prices for low-peak periods. But

the question is how much? Calculating prices must be a delicate balance to create an incentive to switch to low-traffic periods, but not so much that the low-traffic periods become high-traffic periods. Consumer us-age of data turns out to be perfect for this system, however, which is why TUBE is ef-fective. “If you are lost on the street, you would be using your GPS no matter how ex-pensive it is, whereas if you were planning to watch a movie, instead of watching it at 8 PM, which might be a peak time, you might want to watch it from 9 PM if there is a dis-count,” explained Dr. Sen, indicating that while there will always be data that people need in real-time—stock prices and the weather, for example—there are also activi-ties that require no user interaction such as downloading software and cloud data syn-chronization that could be rescheduled for the middle of the night.

TUBE essentially functions as a middle-man between the service providers and the consumers, working in a continuous cycle of measuring aggregate user demand and calculating optimized prices based on that demand. Usage data provided by the ISPs is used to develop a model of the general willingness to shift around data usage from time to time. The model is used to predict usage for the next day and calculate prices

$

data usage

minimum price found→

20092010 2011

Late 2009: The idea of research time-dependent pricing is first considered by EDGE Lab

March 2011: TUBE finishes as a finalist in Vodafone’s Wireless Innovation Project Competition

April 2011 - February 2012: TUBE trial run is conducted with Princeton faculty, staff,students, and their family members

March 2011: TUBE is pre-sented at Princeton’s Keller Center Innovation Forum

February 2010: Research on time-dependent pricing begins

9

engineering

ahead of time; historic data is included from previous weeks to account for changes from day to day, such as the weekends. All the data is fed back into a control loop in a continuous process.

TUBE in your Pocket: DataWizOn the consumer end, TUBE’s technol-

ogy is now available as an app for Android and iPhone—DataWiz. The app features a friendly interface through which users can track their own wi-fi and cellular data us-age to manage their expenses. After a week of usage, the app is able to predict daily caps for users to allow them to optimize data usage. Monthly caps are set either manually or automatically—a limit from the app’s recommendations based on a specific person’s usage—and the app gives notifications when the monthly cap has almost been reached. In addition to these basic functionalities, the app features a lo-cation-based tracker that lets users know how much data they use in each location and the free Voice Over Internet Protocol (VOIP) system, which essentially allows phone calls over the internet so that users won’t exceed their data plans.

Despite the wealth of information it pro-vides, the app also surprisingly nonintru-sive. Every user’s individual data usage is

stored locally on their devices, so the app collects less data about users’ data usage than ISPs themselves, which have to know how much data each user consumes in or-der to know how much to charge them. “We actually developed the model so as to pre-serve as much privacy as possible. We don’t look at which applications you’re using—for the algorithm, we don’t even need to know each individual’s usage,” explained Carlee Joe-Wong, a graduate student in the team. “We’ve tried to make it as minimally inva-sive as possible.”

Future Headings: Taking Technology to the Real World

The project is particularly unique in that it focuses not only on the theory but also on the steps to implementation and com-mercialization. As such, in addition to the research aspect of the TUBE project, the team has also been working to commer-cialize their technology. To that end, they have founded DataMi, a company that grew out of dynamic data pricing research. Com-mercializing the technology, however, is admittedly one of the more difficult parts of the project. Interacting with the users and the companies and making sure the system works seamlessly, as well as coordinating the project across all departments—from

sales, engineering, and management—can sometimes be more challenging than re-search itself, but integrating these compo-nents into the project is also exactly what makes the work done at DataMi very rele-vant to everyday life.

The team presented their research at a myriad of academic conferences from here in Princeton all the way to Italy; ven-ture capitalists and academics alike were thrilled with the idea. The technology is flexible and can be tailored to the needs of each provider and their users; pricing could be time dependent, or could also be applied to other types of data such as text mes-sages and even to systems such as electri-cal usage.

“There has been a growing momentum that this is the right way to start thinking about the future of broadband sustainability and economic viability of the whole internet ecosystem,” said Dr. Sen. “And much of it started from Princeton.”

The research team consists of about 12 people, from undergraduate, graduate and postdocs, development and research staff, and even professional designers. They welcome preco-cious new undergraduates to take part in the research project, from any number of fields in-cluding applied math, computer science, elec-trical engineering, economics, and design.

Set a monthly cap and DataWiz tracks data usage, alerting users when they reach the cap.

A look inside the DataWiz app:

Autopilot mode

App predicts future data usage

Location-based tracking: records gps/wifi information

• Users enter how much they are willing to pay for data

• Users rate how much they are willing to delay the use of each application

• Autopilot mode budgets accordingly, scheduling downloads for when there is less traffic.

For the future? If ISPs were to implement the price incentive system:

2012 2013

2012: Trial period begins with a small ISP in Alaska named Matanuska Telephone Association (MTA), and the sec-ond-largest ISP in India, Reliance Communications; talks with AT&T in the U.S. begin for forthcoming trial

July 30-31 2012: Presented during the first Smart Data Pricing Forum (SDP Forum) in Friend Center, Princeton, with positive feedback

May of 2012: DataMi co-founded

2013: Dynamic pricing models continue to be commercialized

April 2011 - February 2012: TUBE trial run is conducted with Princeton faculty, staff,students, and their family members

August 2012: DataWiz app released

+ $$$ $$

10

engineering

iPhones, tablets, Facebook. Whether we like it or not, technology has rapidly been occupying larger and larger roles in our lives. From online shopping to instant com-munication to GPS systems, technology has greatly simplified day-to-day life, and as a result, we have become increasingly reliant on it. One consequence of such technolog-ical improvements, however, often lurks in the background: how much do technology companies know about us, and what they do with that knowledge?

By using their websites (Facebook, Am-azon, Netflix… etc.), we allow tech compa-nies to obtain large amounts of informa-tion about us – what we buy, what movies we watch, where we are. Naturally, these websites use this information to their ad-vantage, sending their data anonymously to public services, advertising companies, and recommendation services to create more accurate recommendations or present better targeted advertisements. However, these questions then inevitably arise: just how anonymous is this “anonymous” data?; Is it possible that someone could discover your identity solely by analyzing the movies you’ve watched or the items you’ve pur-

chased? Dr. Arvind Narayanan, Professor of Computer Science at Princeton University, strives to answer these questions in his re-search on deanonymization.

At its core, anonymous data is data that, even if publicly available, cannot be traced back to the user. Of course, certain pieces of information are “sensitive,” or key to iden-tifying a person. For example, in 1997 Lat-anya Sweeny showed that knowing just the gender, zip code, and birth date of a random individual was enough to precisely pinpoint his or her identity. As a result, it was com-monly held that as long as such “personally identifiable” information was kept hidden, the data released would be “anonymous.”

In his research, however, Professor Narayanan challenges such a notion. Work-ing with scholars at Stanford University and UC Berkeley, Narayanan conducted re-search on identifying people purely based on their writing styles. You might ask, why study this? Imagine this scenario. You are a political blogger, voicing your discontent at the government’s current policies. However, not wanting to be identified and personally victimized for your beliefs, you use a pseu-donym to obscure your identity. Narayanan, however, has shown that unfortunately, you are not as safe as you think.

Everybody writes in a slightly different style. For example, given two interchange-able words like “since” and “because,” one person may prefer to use “since” while an-

other may prefer to use “because.” Though just looking at a person’s usage of “since” and “because” is not enough, the combi-nation of thousands of such markers put together enables a computer to compile

a thorough database on different people’s styles of writing. In his research, Narayanan was able to develop an algorithm to iden-tify an author of a blog post solely through analyzing the author’s writing style. By feeding a computer 100,000 different blogs, Narayanan then picked a blog written by an author who also had another blog included in the 100,000 blogs. The program was still able to find this second blog among the 100,000 and match it to the correct author, solely based on the author’s writing style.

Such research, as Narayanan describes, could have huge implications. If you were that “anonymous” political blog-ger, someone could potentially scan all of the blogs online and determine who you are purely based on your writing style. Because of the potential gaps in ano-nymization, Narayanan is now focusing on developing a new way to create web-sites – privacy-conscious system design. While it is possible for companies to build websites in a way to inherently protect pri-

privacy, please: expanding identities in the Digital world

By Eugene Tang: Interviewing Professor Arvind Narayanan

since

because

Just how anonymous is the infor-mation collected from you over the Internet? Dr. Arvind Narayanan’s research on deanonymization strives to answer these questions.

Prof. Narayanan was able to develop an algorithm to identify the author

of a blog post just by analyzing and comparing the writing style.

Designed by Angela Zhou

11

engineering

vacy, Narayanan also recognizes the many . challenges to be faced in such a process. Economically, companies currently do not have much of an incentive to build more privacy-conscious websites – if consum-ers complain about privacy, companies can compensate by simply adding a few extra privacy features. Additionally, it is very dif-ficult to define what does or does not invade privacy.

To better understand privacy, Narayanan proposes that it is necessary to re-verse-engineer websites and quantifiably measure how they use their consumers’ information.

Reverse-engineering websites could take on many forms, but at its core, it is basi-cally a way to discover how exactly a web-site interacts with its users. For example, in another piece of research performed with fellow scholars at Princeton University, Narayanan studied how certain websites stored cookies, small bits of code used to

track information on mobile and desktop devices, and what information the websites obtained about their users from the cook-ies (some cookies actually stored the user’s browsing history). For Narayanan, it is only through such an understanding that we can develop a better means for protecting pri-vacy online.

With the growing role of technology in society – from iPhones to tablets to Face-

book – new issues arise, especially that of privacy. It is not the act of companies col-lecting data about us that is worrying; in many ways, it actually improves our lives. Rather, it is what they do with the data that can be a huge concern. There is yet a long road ahead to understanding the relation between data and privacy, but Narayanan is taking great strides forward to achieve such an understanding.

Reverse-engineering a website to discover how it interacts with users in order to arrive at a more privacy-conscious systems design. Left: Typical systems architecture, with unsecure interactions and added privacy features. Right: an application secure from the very beginning.

It is only through an understanding of how companies use consumer data that we can develop a better means for protecting privacy.

12

Budget Cuts

loss of innovationIt is no secret that much of the research

conducted at Princeton is funded by fed-eral agencies. According to President Shir-ley Tilghman, the University receives ap-proximately $250 million annually. These government grants and contracts are a major source of funding for Princeton’s cut-ting-edge research in engineering, applied sciences, natural sciences, mathemat-ics, social sciences, and the humanities. They come from organizations such as the Department of Energy (which is the sole funding source for the Princeton Plasma Physics Laboratory), the National Institute of Health, the National Science Foundation, and the Department of Defense.

Unfortunately, these sources of funding are now in jeopardy because of the seques-ter. Sequestration refers to the creation of budget caps, which, if exceeded, result in automatic general cuts. These budget caps apply to discretionary domestic spending, which includes federally-funded research. Congress implemented sequestration when it passed the Budget Control Act of 2011, its temporary solution to the 2011 debt-ceiling crisis. The act mandated general cuts to discretionary domestic spending if a Con-gressional Joint Selection Committee on Deficit Reduction did not meet its Novem-ber 2012 deadline of cutting $1.5 trillion from the federal budget over the course of

10 years. Unfortunately, the committee did not meet this deadline.

After a few months of political debates concerning the so-called fiscal cliff, the first round of cuts were enacted on March 1, 2013, with approximately $85 billion be-ing cut from the discretionary parts of the federal budget for fiscal year 2013 (a 5% reduction). As President Tilghman explains, “Five percent doesn’t sound like a large amount, but it’s actually a very significant amount.”

But 5% isn’t even the end of it, as addi-tional cuts are set to go into effect each fiscal year barring any new legislation, with the next round of cuts set to occur in Octo-ber. “What we’re all terrified about is what happens October 1st. There’s always the worry at times when funds are really tight, that it starts to influence the kind of work that goes on,” said Tilghman. “One of the things I’m sure you’ve already figured out in science is that low-risk science tends to be boring science and not impactful science.”

Tilghman fears that even the perception of decreasing levels of funding will result in less effective “low-risk” research.

The impending issues of October aside, it is clear that the current budget cuts will trickle down from the federal agencies to Princeton University. For example, training grants for graduate students, undergrad-

uate summer programs, and lab material costs could be affected. Tilghman felt that senior thesis funding would not be in jeop-ardy due to their relatively low cost. How-ever, she conceded that the lab materials and equipment used by seniors are all ulti-mately paid for with federal funds.

“Our investigators who’ve made commit-ments to experiments, to people, would suddenly have less money than they thought they were going to have,” said Tilghman.

Tilghman explained how particular agen-cies might impact departments at Prince-ton differently. NIH funding will be critical for the Molecular Biology department, while Department of Energy funding will shape the future of the PPPL. The severity of the cuts will depend on how these or-ganizations decide to make their 5% cuts. The NIH, for example, could decide to issue no new grants for the next year, reduce all grants by 5%, or to carefully analyze which programs can be cut more or less in order to reach the overall goal of a 5% cut. On the other hand, the PPPL’s future is already un-certain, as they never received a fiscal year budget for 2013. The lab has been working under fiscal year 2012 guidelines, knowing that cutbacks are sure to come. They have yet to receive instructions from the Depart-ment of Energy on how the sequester’s impact on the DOE will trickle down to the

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$6.3B CUt

$2.4B

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amount that federal agencies currently give annually to fund Princeton research

$323M

interviewing university president shirley Tilghman

By meredith Wright

Edited by abrar Choudhury, Nassim fedel, Samuel Kim, and Kiran Vodrahalli

also featuring Prof mark rose, Prof Sam Wang, Dr. Ethan Perlstein

Designed by Eugene Lee

amount cut from federal agencies that fund Princeton research

13

PPPL. Finally, the Andlinger Center for En-ergy and the Environment will also be im-pacted, due to the large grants it receives from the Department of Energy.

Princeton’s investigators are keenly aware of the murky future ahead for their research. Many have reached out and writ-ten to their representatives on the issue. Others have already started scaling back expenses. “Although the scientific commu-nity has long been subject to insufficient funding for basic research, the sequester will make the problem much more severe,” said Professor Mark Rose, Director of Un-dergraduate Studies for Molecular Biol-ogy. “I don’t think that people realize that the mere threat of the sequester, together with the delay in passing a federal budget for 2013, has already had a significant neg-ative impact on research.” Rose explained that proposals that would have been funded last year may have to wait months to re-ceive funding decisions from the NIH this year. “Even if grants are eventually funded,

it may be too late to retain the researchers who were paid on that grant. The result is not good for science and not good for the country.”

According to Professor Sam Wang, As-sociate Professor of Molecular Biology, a partial remedy for scientists could be found in various alternative funding sources, such as foundations, corporations, and individual donors. However, it is unclear if they will be enough for the basic science research that occurs on our campus. This is especially true for basic research without clear med-ical applications or the potential for com-mercialization.

With federal funding unquestionably an issue and traditional alternatives unlikely to provide real results, researchers will be forced to become more creative in where they seek funding. Crowdfunding, where researchers advertise a project idea on-line and raise donations from the general public, could be a temporary fix for the lack of funds. Ethan Perlstein, a former Lewis-

Sigler Fellow, suggests a three-pillar ap-proach for fellow scientists battling bud-get cuts. These pillars involve researchers seeking online donations from small do-nors through crowdfunding, larger grants from foundations and advocacy groups, and gifts from individual philanthropic ‘angels.’ Like many of Princeton’s scientists, Perl-stein emphasized that the lesson of se-quester is that researchers can no longer be dependent on one source of funding in order to continue doing exciting work.

Right now, Princeton’s scientists are in limbo waiting for the federal agencies to make decisions on budgets and grants, but the outlook undoubtedly looks grim. Hope-fully, the agencies will make cuts that do not hold back Princeton research. Other-wise, researchers may find that in order to get funding, they will need to pursue less ambitious projects or become creative in their endeavors.

CUT fUnding

The ThRee pillaR appRoach To FunDing

WhaT ElsE CoUld BE CUT?

research is funded by priority, which favors “low risk” research. this results in a shift towards safer, but typically less innovative research.

croWd-fUnding grants

angelinvestors

fUnding$$

there’s still hope for researchers who lose out from the sequester.

?

lab materials & eQUiPment Undergrad sUmmer Programslab training

14

biology

N o t w o s N o w f l a k e s

are IdenticalTakE a momENT aND look aT yoUR HaND. yoUR RigHT HaND.Watch the tendons flex as you stretch out your fingers, examine the blue and purple blood vessels peeking through your skin. Look at the conformation of wrinkles around your knuckles, and the lines snaking across your palm. Now look at your left hand as well. Hold them both out, together. Isn’t the symme-try remarkable? The corresponding components are nearly identical

Professor Thomas Gregor and his biophysics Laboratory for the Physics of Life have investigated this very symmetry in the wings of a particular spe-cies of fly, Drosophila melanogaster, in specific relation to reproducibility: the level of similarity of a biological component across different members of the same population. However, while symmetry within an individual is cer-tainly remarkable, it is also ubiquitous in the natural world. We see bilateral symmetry in mammals, radial symmetry in starfish, spherical symmetry in some protozoa, and even approximately infinite fractal self-similarity in nu-merous plants. Reproducibility, on the other hand, is quite rare.

by Julia Metzger interviewing Professor thomas Gregor

15

biology

designed by stephen Cognetta

The saying goes, as we all know, that no two snowflakes are ever the same. Accordingly, understanding the biological mechanisms by which organisms generate macroscopically symmetric body parts, as well as macroscopically reproducible individuals within a species, is an area of intense research. The relationship between the two is also an area of interest; it is one thing to have our own hands nearly iden-tical, but imagine holding up one’s hand and comparing it to the hand of a friend – logically, we would conclude that the level of symmetry within an individual would exceed reproducibility across a population. So, too, in Professor Gregor’s studies of the symmetry and reproducibility of wings in Drosophila melanogaster, wings of a certain individual are bound to be more similar to one another than to other mem-bers of the population.

Or so one would think. Professor Gre-gor’s findings have indicated that symme-try and reproducibility for wing shape in the species of Drosophila melanogaster are, in fact, essentially equal. In inbred fly lines raised at a constant temperature, the fluctuations in shape and variation of bilateral symmetry correspond to the same level of disparity in reproducibility in a pop-ulation. This amazing relationship between symmetry and reproducibility resulted from Gregor’s investigation of underlying developmental mechanisms using the wing as an ideal starting point. According to

Gregor, “the wing is easy to measure: you can rip it off, plop it on a microscope, and measure it in two dimensions.” Extracting meaningful and statistically significant results requires a vast amount of collected data, and the structure of the wing lends itself to this type of analysis.

Gregor and his lab compiled morpho-metric measurements of landmark points on the wing (see figure to the left) across 500 adults of different strains, and from these measurements they were able to glean powerful insight into the specific developmental mechanisms that generate this remarkable symmetry and reproduc-ibility in the fly, as well as the fascinating relationship that they are approximately equal. Gregor began with two possible schemes for how biological organisms obtain symmetry and reproducibility through the complex network of Drosophila melanogaster larval development – where 15 genes generate 6,000 cells in just 3 hours. In the first scenario, a vast number of complicated mechanisms are required to strictly control and regulate shape and size throughout this entire developmental process in order to result in symmetric macroscopic body parts. The second is far simpler, entailing the construction of initially symmetric conditions that remain ultimately symmetric through exact repli-cation on each side, but it, too, is subject to a limiting factor: the success of this method is likely dependent on fluctuations

in development, environment, and genet-ics.

Gregor was able to relate his measure-ments of symmetry and reproducibility in the macroscopic wing to microscopic mag-nitudes during development – and both are approximately the size of a single, indi-vidual cell. With this metric, he linked the macroscopic readout of bilateral symmetry and population reproducibility with the underlying molecular details of embryonic development. Thus the resulting power of Professor Gregor’s results is that the second scenario is the governing process of generating wings in the development of Drosophila melanogaster, and it is a “beautifully simple and elegant mecha-nism: as long as seeds on the left and right are similar and the steps are conducted reproducibly, we obtain the same result in the end.”

In and of itself this research has pow-erful implications for the developmental processes of drosophila, but even further frontiers exist as well. Gregor hopes to perhaps investigate the interplay between symmetry and reproducibility in other organs of the fly, as well as investigate specific changes in inbreeding and temper-ature. Gregor has certainly challenged our notions of symmetry and reproducibility in the natural world, and so we wait eagerly to see what other conclusions his research will draw.

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Ever wonder how our brains are able to grasp complex activities, such as playing an instrument or driving a car? How about riding a bike or turning a doorknob? Such everyday activities, called “motor-sequence behaviors,” are a fascination to neurosci-entists around the world because they re-quire a precise coordination between many different groups of brain cells, or neurons, and muscles. Here at Princeton, Dr. Andrew Leifer of the Lewis-Sigler Institute for Inte-grative Genomics is studying this very phe-nomenon. His work attempts to understand how different connections between neurons are responsible for such coordinated be-haviors and habits in organisms.

“Currently, we know how individual neu-rons function, and how large areas in the brain are related to behavior,” explains Dr. Leifer. “But what we don’t know is how small neural circuits can play a role in be-havior. How are small, individual neural circuits relevant to behavior? How can they affect stuff like motor memory and addic-tion, etc?” Dr. Leifer’s goal is to understand how different combinations of neurons can result in this coordination of complex movements so fluidly in everyday life. He approaches this research by using what biologists call “model organisms,” specif-ically the worm C. elegans. These worms are useful because scientists have fully mapped out the genome of the worm, and know how every single cell in this worm is

created and dies, and how all 302 neurons of this worm are connected, and therefore there is a large knowledge basis that can be used for researchers to take advantage. Dr. Leifer activates or inactivates individual neurons in the worms to see how that af-fects motor sequence behaviors, such as turning around when the worm bumps into an object. But how is it possible to activate or deactivate one or two specific neurons in an organism? How is it possible to un-derstand how all the neurons in C. elegans interact with its approximately 100 muscle cells, both directly, and indirectly, to coor-dinate various motor-sequence behaviors? Dr. Leifer and other neuroscientists have ingeniously implemented a novel technique in neuroscience, called optogenetics, to aid in their research.

In optogenetics, scientists force neurons to express special proteins. These proteins, depending on which ones the researchers use, can either activate or inactivate the neuron or group of neurons, when hit with a specific color of light. For example, the pro-tein channelrhodopsin-2 activates neurons that express it when those neurons are hit with blue light, and the protein halorhodop-sin inactivates neurons that express it when those neurons are hit with yellow light. In this way, neuroscientists can specifically ask how changing one neuron can affect the behavior of an entire organism! For ex-ample, in the worm C. elegans, optogenetic

activation of the worms’ sensory neurons causes the worm to back up, turn around, and continue to move in a random direc-tion different than before. This reaction is the exact same as the worm’s reaction to bumping into an obstacle. Expressing ha-lorhodopsin in the worms’ sensory neu-rons and shining yellow light on the worms, however, prevents this behavioral response when the worms swim into an obstacle! In

some cases, the results are very surprising, and scientists have concluded that some specific neurons are essential for some very important behaviors of model organisms. Furthermore, researchers can use complex genetic engineering to get these proteins expressed in any neuron of their choosing, hence the name optogenetics (opto → light, genetics → controlling protein expression). Optogenetics is widely used in model or-ganisms, such as rats and mice, to control neural circuits, and in turn study the func-tion these neurons have in behavior in these organisms.

Because the anatomy and genetics of the worm C. elegans are so well known, and because these worms are optically trans-

Shedding Light on the Mysteries of the Brain and Behavior

By Neil Mehta interviewing Dr. Andrew Leifer

Researchers can use complex genetic engineering to get these proteins expressed in any neuron of their choosing.

Designed by Jessie Liu and Erica Tsai

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parent (visible light can shine right through them), these worms make an ideal model organism for Dr. Leifer’s experimentation. Using the concept of optogenetics, Dr. Leifer has created a novel experimental de-sign that allows him to track the movement of his worms over time and therefore see changes in worm behavior over time when optogenetically stimulating the worms! A microscope camera that can follow the worm movement visualizes the worms. Sensors associated with the camera allow

lasers constantly point at a single neuron or a group of neurons, allowing Dr. Leifer to continuously track changes in worm behav-ior. Dr. Leifer hopes that this experimental technique will help him and his lab shed light on motor-sequence behaviors using the worm C. elegans as a model organism.

Currently, neuroscience research is at the brink of understanding how seemingly sim-ple behaviors arise from extremely intricate and complex neuronal interactions, and the implementation of optogenetics plays a key

role in understanding how these complex interactions form and work. Dr. Leifer’s fascinating new methodology of using opto-genetics in real-time with worms will hope-fully shed new light on how the brain can coordinate seemingly complex behaviors so flawlessly. Dr. Leifer strongly believes that understanding how the brain of model or-ganisms function will eventually help shed light on how the human brain is responsible for such unimaginably amazing feats.

Lenses and mirrors are required to shine laser light onto the digital micromirror device (on the right) before head-ing into the microscope (not pictured on left). Photo by Elizabeth Kane.

Unregulated C. elegans worm movement

Induced omega-turn in C. elegans worm movement

Laser-Induced Behavior in C. elegans

A laser beam is shined on neurons being studied, activating them and inducing specific behaviors in C. elegans

Laser

Before After

by Cissy Chen interviewing Professor Christopher tully (PHy)

the Search for the oldest relic of the Universe:PtolEmy at Princeton

νrElIC NEUtrINoS: “[N]eutral, nearly massless particles... at temperatures colder than deep space...”

Electrons climb an energy hill as they are pushed toward a magnet. only electrons with high energy make it through the first filter.

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When an electron leaves the second filter, it hits a detector that measures the energy added by the neutrino interaction.3Electrons accelerate through a second

magnetic field. as they orbit, this more selective filter determines which high energy electrons will pass through.2

designed by rory fitzpatrick

As archaeologists dig for the oldest signs of civilization on Earth, physicists here at Princeton have embarked on a different pursuit: the search for the oldest relics from the early universe that could bring with them a wealth of information about the history of the universe. These ancient relics of the universe are neutral, nearly massless and nearly frozen particles that are called relic neutrinos. They were created just a sec-ond after the universe is predicted to have begun.

Professor Christopher Tully of the Prince-ton Physics Department developed an experiment called PTOLEMY (Princeton Tritium Observatory for Light, Early-Uni-verse, Massive-Neutrino Yield) to search for these neutrinos. The motivation behind this experiment, according to Professor Tully, is simply that “modern science is so convinced that these Big Bang neutrinos have to be there that anything other than the right answer would completely change our belief about how the universe began.”

Theorists have predicted that there are about 330 neutrinos per cubic centime-ter everywhere in space – that means that

there are probably millions moving around you right now. Though these predictions are supported by the current body of scien-tific knowledge, these neutrinos have never been detected. And as Prof. Tully says, “it’s something so fundamental because most of space is permeated with it, but for physi-cists, it’s just hard to go on without looking.”

But looking is one thing; finding is another. These neutrinos, as pervasive as they are predicted to be, are extremely difficult to detect because they move around with such low energy that we need very high precision tools to make these measurements. Much of the work in the PTOLEMY experiment in-volves building energy filters to make these measurements.

The key concept is to use an unstable ma-terial whose natural decay process is sped up by a neutrino interaction. Tritium, the third isotope of hydrogen, is ideal for this. Thanks to the Princeton Plasma Physics Laboratory, PTOLEMY has access to sub-stantial amounts of tritium that can be spread very thinly (to a couple of atomic layers) over a large area (the size of a foot-ball field). The tritium sheet acts like a thin

sail for neutrino “wind.” When tritium de-cays naturally, electrons are produced with a wide range of energies – but when neu-trinos interact, these electrons will have a unique and slightly higher energy. There-fore, PTOLEMY must use tools that mea-sure this increase in energy very precisely.

The idea of the method is simple: PTOLEMY aims to let an electron run through multiple energy “filters” to precisely measure the energy of a single electron from this de-cay. In the first filter, all of the electrons are pulled to a magnet and forced to climb a very precisely carved energy “hill,” like a roller coaster on an upward ascent. Only the most energetic ones can get over this energy “hill,” so the low energy electrons are filtered out. Some of these higher en-ergy electrons may have come from neu-trino interactions, but not all. So then they are pushed through another more selective filter by accelerating them through a mag-netic field again. These electrons move in an orbit and emit radio waves at a certain frequency. With a very precise antenna, we can measure these frequencies. When a single electron passes the frequency

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threshold for an electron that was emitted due to a neutrino interaction, it continues moving and hits an extremely sensitive de-vice. It is balanced precariously between two different states, as though on the tip of a pin. When a little bit of energy is added by the electron, there is such a sharp phase transition of this device (i.e. the pin tips over to one side), that it is possible to measure exactly how much energy was added, and thus find the energy of the single electron. By examining this energy, physicists will be able to count the number of neutrinos that interact with the tritium.

A fully functional prototype of this exper-imental model has been constructed, but the PTOLEMY team is still working on im-provements to the tools. Once constructed, this experiment could result in a number of drastically different observations about the universe. First, detecting too many neutri-nos could possibly contradict the Big Bang theory, the long accepted theory of the his-tory of the universe. In fact, this observa-tion would suggest that there wasn’t just a single Big Bang: perhaps these neutrinos came from multiple other Big Bangs. Or, if

no neutrinos are found, we may simply need to reconsider the lifetime of the neutrino – perhaps most of these relic neutrinos have decayed in the past 13 billion years. Fur-thermore, PTOLEMY has the power to cap-ture a special type of predicted neutrino that cosmologists think may explain the mysterious substance that we cannot see or detect, dark matter, which is thought to make up about 85% of the total mass of the universe (the other 15% comes from nor-mal matter, like the atoms that make up our visible universe).

Although still in its beginning stages, this experiment will create a great new obser-vational machine, which, over time, will be used to quantify more and more observa-tions about the universe. Currently, the biggest experimental challenge is keeping the experiment, especially the device that is balanced between two states, at a very low temperature (ten times colder than deep space) to achieve the desired preci-sion. This has never been done before with

such a large experimental setup, but phys-icists at PTOLEMY are working on achiev-ing these extremely low temperatures. The techniques and tools from PTOLEMY will contribute to many areas of science and im-aging processes that require high precision energy measurements.

Detecting these elusive relic neutrinos could finally experimentally verify (or con-tradict) a prediction that has been accepted for quite some time on theoretical grounds. Understanding these relics from just a sec-ond or two after the predicted Big Bang would allow us to experimentally probe the very beginning of matter formation in the universe, preempting a crucial time in which the most fundamental ingredients of our universe were formed. And although neutrinos seem so insignificant, as if the universe would just behave quite the same way it does without them, it turns out that they are, in the words of Professor Tully, “a tiny ingredient of the universe that makes it all work.”

✓tHEorIES VErIfIED

ν?

rEtHINK NEUtrINo

rEtHINK UNIVErSE

?

330 neutrinos and anti-neutrinos per cubic cen-timeter

“[nEUTrinos arE] a Tiny ingrEdiEnT of ThE UnivErsE

ThaT makEs iT all Work.” — ProfEssor TUlly

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conseQuences oF ReseaRch

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“

A single bird is nothing out of the or-dinary. But thousands of them, swiftly swooping and swerving in unison, with-out colliding into each other, and cre-ating beautiful, fluid forms is a very impressive marvel of nature. Likewise, while a single ant is a typical six-legged insect, a giant swarm of ants is a whole other beast in itself. Termites, blind creatures, manage to create massive, functional mounds. They manage to collectively facilitate this process with-out any direct communication between them. These phenomena motivate researchers like Professor Bernard Chazelle to study natural algorithms. According to Professor Chazelle, algo-rithms, which are step-by-step proce-dures used predominantly in computer science to reach an end goal, represent the future of scientific research be-cause of their ability to model complex, dynamic systems.

Computer scientists design algo-rithms that are tailored to accomplish a specialized task or goal. Algorithms, as we know them conventionally, are engineered; they are products of hu-man creation. As a result, applying an algorithm to nature may be counterin-tuitive—how can a manmade construct be found in the world around us?

The answer lies in the fact that most biological systems are far too complex to be explained by differen-tial equations, which were the primary tools used to study science in the 20th century. Thus far, differential equations have embodied some of the simplic-ity and elegance of science. Physical phenomena, like heat transfer or par-ticle motion, can often be expressed quite succinctly, with a few operators and symbols. “A differential equation,

which you can write in one line, pretty much gives the entire solution to the problem,” says Professor Chazelle. Al-though the study of physics can become quite complicated the forces driving it can be simplified and abstracted into a few lines of equations which can make predictions about physical behavior. Differential equations, however, are not enough for the natural world. “In the living world, everything is more com-plicated than traditional physics,” re-marks Professor Chazelle.

A better way to think about natural systems, according to Professor Cha-zelle, is that “biology is equal to physics plus history.” The millions of years of life that preceded us have played piv-otal roles in shaping the wonders we observe today. Professor Chazelle fur-ther explains that what we see in biol-ogy stems from the occurrences of all eras past:

“From natural selection and evolution, and so on, all these changes have ac-cumulated, and complexity has grown, but that’s not true in physics. When you drop a pebble, you could have dropped that pebble a million years ago and ex-actly the same law would have applied.”

Because of this complexity we in-herit from evolutionary history, only algorithms are able to help us under-stand how these complex events—birds flocking, ants swarming and mound building—can be coordinated.

Due to all this complexity, the field of natural algorithms lends itself to a multidisciplinary approach. Conse-quently, Professor Chazelle works with a variety of other experts in fields rang-ing from biology to physics in order to

Natural AlgorithmsA New Way to Study the Natural World

By Elizabeth YangWith Professor Chazelle

Professor Bernard Chazelle is a computer science professor who

specializes in theoretical computer science, namely algorithms. His research explores the new field of natural algorithms, which provides us with an innovative way to think about science. “

Changes in how organisms behave have accumulated over time as com-plexity has grown.

Biology is equal to physics plus history.

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study these natural algorithms. He is currently working on projects involving synchronization, a central theme that is at the core of many biological and behavioral pro-cesses. For instance, an orchestra could very well play without a conductor because each individual under-stands how to engage in synchronization with the rest of the group. The tens of thousands of electric cells in the heart also manage to completely synchronize to gener-ate a heartbeat. Less helpfully, the neurons of epilep-tic patients all synchronize when they are not meant to, leading to seizures. Clearly, studying synchronization in an algorithmic way would give us a greater understand-ing of very relevant biological processes.

Professor Chazelle is also applying the idea of synchro-nization to a topic in sociology—namely, generating a consensus. While it is nearly impossible to have a group of people completely agree on an issue, there is usually a moment when a group hits a consensus, an equilibrium point of sorts at which opinions are no longer chang-ing. The process of reaching this consensus, a state in which people’s views stabilize, is called convergence. Professor Chazelle investigates key questions relating to convergence, such as, under what circumstances do we converge? And, under what circumstances do opinions change over time? During his investigations, he hit upon the interesting result that people never change their minds at random. In fact, when people do change their minds, they do so in a very predictable fashion, which we can, to some extent, foresee through the lens of natural algorithms.

As we expand our explorations into science and tech-nology, algorithms are going to be a new tool that will become increasingly important to scientists and re-searchers. “Algorithms give a narrative, and tell a dy-namic story”. Just as differential equations once led to breakthroughs in science, algorithms can now revolu-tionize our understanding of the living world and science in general. Algorithms not only account for the com-plexity generated by years of history, but they are able to show us the actual processes by which nature cre-ates these fathomlessly complex systems. Natural al-gorithms are absolutely revolutionary, and the develop-ment of this significant concept lives right in Princeton’s own computer science department.

slower

faster

An example of natural algorithms at work: colonies of fireflies synchronize their glowing on a macro-scale by the individual’s micro-scale response to the frequency of neighboring fireflies’ blinking.

Each individual musician understands how to synchronize with the group.

People change their minds in a predictable fashion.

Neurons synchronize during epileptic seizures.

Our galaxy alone contains 300 billion stars, most of which, we now know, have planets around them. Before 1995, nobody had discovered a single planet outside our Solar System. By 2013, over 860 planets have been positively identified, with tens of thousands of candidates awaiting confir-mation. With this flood of discoveries, many fundamental questions are beginning to be answered. How many planets are there? How did they form? What are they made of, where do they orbit, and how many are suit-able for life? Every night, telescopes scan the sky, monitoring the stars to discover even more exoplanets. Two of the most successful exoplanet search projects have been HATnet and HATsouth, both conceived by Assistant Professor Gaspar Bakos and now managed by Harvard’s Center for As-trophysics.

Both endeavors consist of completely automated telescopes inside of protective domes. HATnet, established in 2003, has 6 small 11 cm telescopes at two sites, Arizo-na and Hawaii. HATsouth, installed in 2009, has six 18 cm telescopes: 2 in Chile, 2 in South Africa, and 2 in Australia.

HAT, like most exoplanet searches, uses the transit method. After the internation-al HAT team selects a target region, the telescopes automatically image the region night after night. Astronomers use these photos to monitor the brightness of every

star in the region. If a planet orbits its star at the right angle, it periodically passes in front of the star, causing an apparent dip in the star’s brightness—the bigger the plan-et, the larger the dip. When more than one transit is observed, astronomers can calcu-late the planet’s orbital period, which leads directly to its distance from its star—the shorter the distance, the shorter its orbital period. The detected signal is now a plane-tary candidate. In order to verify that it actu-ally is a planet, follow-up observations usu-ally attempt to detect it by measuring the

Doppler shift of its star’s light, caused by the planet’s gravitational force as it orbits the star. If this is successful, astronomers would know the planet’s mass, radius, and orbital distance.

Every night, HAT’s mini-observatories use their sensors to measure wind speed, hu-midity, cloud cover, precipitation, and near-by lightning strikes. If the weather is just right, the dome opens and the telescope uses its CCD camera to take pictures of a single area of the sky, 8x8 degrees in area, from dusk to dawn. This area is roughly the

= location of HATnet telescopes = location of HATsouth telescopes

HaTnet: The Search for Extrasolar Planets

By Michael Zhang interviewing Professor Gaspar Bakos (AST)Designed by Erica Tsai

***HAT-P-2b shown in comparison to Jupiter

Radius: approximately equal to JupiterMass: 9x that of JupiterCharacterized by an eccentric orbit

***HAT-P-11b shown in comparison to Neptune

Radius: 42% that of JupiterMass: 8% that of JupiterCharacterized by a highly inclined orbitKnown as “Hot Neptune“ (an extrasolar planet in an orbit close to its sun, with a mass similar to that of Uranus or Neptune)

size of a fist held at arm’s length—extreme-ly large for an astronomical telescope. When the weather deteriorates or sunrise approaches, the domes close, the tele-scopes stop tracking their targets, and re-searchers can access their data through the Internet. The system is entirely automated and built using open-source software. HAT-net now monitors more than 100,000 stars every year, for a lifetime total of 700,000; HATsouth monitors 400,000 and is outpac-ing its predecessor in its rate of discoveries.

These automated observatories were first envisioned by Bakos in 1998. At the time, he was a year undergrad in Hungary, and planned to use them not for planet hunt-ing, but for astronomers to point telescopes at gamma-ray bursts as soon as they are discovered. “It seemed to me like a sub-optimal procedure that you get a phone call from a guy in Europe, who was woken up by his cellphone, then he calls me up, then I answer the phone, then I put down the phone, then I stop my observation…just very suboptimal in the age of Ethernet and robots. The telescope should just respond to a trigger and point to the right position,” said Bakos. His focus quickly shifted from gamma rays bursts to monitoring the sky for variable stars, and by 2000, Bakos had built a working prototype.

Meanwhile, he moved to Harvard’s Center for Astrophysics at a time when astrono-

mers there were extremely enthusiastic about looking for planets, convincing him to dedicate his invention to planet hunting.

HAT can reliably measure 1% dips in a star’s brightness, and has discovered 50 planets to date. Most of these planets are hot Jupiters—enormous planets much heavier than Jupiter, and orbiting so close to their stars that they complete one orbit in days. As with any transit survey, large planets with short orbital periods are much easier to detect than Earth-like planets that orbit once every 365 days. In reality, small-er planets like the Earth, which orbit their stars at large distances, are overwhelming-ly more common, a trend that holds to the limits of current human technology. HAT has the ability to detect super-Earths, plan-ets a few times Earth’s mass, or 100 times less massive than Jupiter. HAT can even detect a super-Earth in the Habitable Zone of a small star. “We made simulations and calculations and yes, there is a possibility, but it would be extremely surprising,” Ba-kos claimed.

Since its inception, HAT has detected a wide variety of planetary systems. HAT-P-2b, the first supermassive Jupiter for which scientists measured an accurate radius, is a gas giant the size of Jupiter but 9 times its mass. Its orbit is so eccentric that it comes as close as 7.4 million and as far as 25 million km from its star. HAT-P-32b

is 8 times Jupiter’s volume but around the same as Jupiter mass. Its density is so low that scientists are still puzzled as to how it could have formed. HAT-P-11b, only 8% the mass and 42% the radius of Jupiter, was the first transiting “hot Neptune” discovered from the ground. Finally, the star HAT-P-13 has 2 planets: an inner planet with a 2.9-day orbit and 0.8 Jupiter masses, as well as an enormous outer planet with 16 Jupiter masses and a 446-day orbit. This was the first system where a transiting exoplanet was confirmed to be accompanied by a sec-ond planet.

HATnet and HATsouth are just two of many ongoing exoplanet search projects. Su-per-WASP employs a similar methodology, and has discovered 80 planets. The Kepler spacecraft has discovered 2700 planet can-didates since its launch in 2009. It has al-lowed scientists to estimate that our galaxy contains 2 billion habitable Earth-like plan-ets around Sun-like stars, of which Kepler is expected to discover at least one. Recent-ly, spectroscopy of large extrasolar planets has become possible, allowing astronomers to determine the chemical composition of their atmospheres. In several years, the next generation of telescopes will be capa-ble of analyzing the atmospheres of Earth-like planets to search for signs of alien life.

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