Snowflake Science

Caltech Physicist Explains Why Snowflakes Are So Thin and Flat

We've all heard that no two snowflakes are alike. Caltech professor of physics Kenneth Libbrecht will tell you that this has to do with the ever-changing conditions in the clouds where snow crystals form. Now Libbrecht, widely known as the snowflake guru, has shed some light on a grand puzzle in snowflake science: why the canonical, six-armed "stellar" snowflakes wind up so thin and flat.

Few people pay close attention to the form that snow crystals—a.k.a. snowflakes—take as they fall from the sky. But in the late 1990s, Libbrecht's interest in the tiny white doilies was piqued. The physicist, who until then had worked to better understand the sun and to detect cosmic gravitational waves, happened across an article describing one of many common snowflake structures—a capped column, which looks something like an icy thread bobbin under the microscope. Such a snowflake starts out, as all do, as a hexagonal crystal of ice. As it grows, accumulating water molecules from the air, it forms a tiny column. Then it encounters conditions elsewhere in the cloud that promote the growth of platelike structures, so it ends up with platelike caps at both ends of the column.

"I read about capped columns, and I just thought, 'I grew up in snow country. How come I've never seen one of these?'" Libbrecht says. The next time he went home to North Dakota, he grabbed a magnifying glass and headed outside. "I saw capped columns. I saw all these different snowflakes," he says. "It's very easy. It's just that I had never looked."

Since then, he has published seven books of snowflake photographs, including a field guide for other eager snowflake watchers. And his library of snowflake images boasts more than 10,000 photographs. But Libbrecht is a physicist, so beyond capturing stunning pictures, he wanted to understand the molecular dynamics that dictate how ice crystals grow. For that, he's developed methods for growing and analyzing snowflakes in the lab.

Now Libbrecht believes he's on his way to explaining one of the major outstanding questions of snowflake science—a question at the heart of his original interest in capped columns all those years ago. Scientists have known for more than 75 years that at conditions typically found in snowflake-producing clouds, ice crystals follow a standard pattern of growth: near -2°C, they grow into thin, platelike forms; near -5°C, they create slender columns and needles; near   -15°C, they become really thin plates; and at temperatures below -30°C, they're back to columns. But no one has been able to explain why such relatively small changes in temperature yield such dramatic changes in snowflake structure.

Libbrecht started his observations with the thinnest, largest platelike snowflakes, which form around -15°C in high humidity. Some of these snowflakes are about as sharp as the edge of a razor blade. "What I found in my experiments," Libbrecht says, "is a growth instability, or sharpening effect." He noticed that as a snow crystal develops at -15°C, the top edge starts to develop a little bump of a ledge, which gets sharp at the tip. Basically, the corners stick out a bit farther toward the moist air, so they grow faster. And a cycle begins: "As soon as the ledge gets a little bit sharper, then it grows faster, and if it grows faster, then it gets sharper still, creating a positive feedback effect," Libbrecht says. "In the atmosphere, it would just get bigger and bigger and thinner and thinner, and eventually you'd get a really nice, beautiful snowflake."

If this sharpening effect occurs at other temperatures, which is likely, then it explains how small changes in temperature can yield such wildly varying snowflake structures. "The sharpening effect can yield thin plates or slender columns, just by changing directions," Libbrecht says. "That's a big piece of the puzzle, because now you don't have to make these enormous changes to get different structures. You just have to explain why the instability tips to produce plates at some temperatures, and tips to make columns at other temperatures. The flip-flopping of the sharpening effect nicely explains how the ice growth rates can change by a factor of 1000 when the temperature changes by just a few degrees.”

Libbrecht can't yet fully explain the underlying molecular mechanisms that produce the sharpening effect or exactly why different temperatures lead to sharpening on different faces of growing snow crystals. "But," he says, "this is a real advance in snowflake science. Now you can explain why the plates are so thin and the columns are so tall."

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Caltech-Led Team of Astronomers Finds 18 New Planets

Discovery is the largest collection of confirmed planets around stars more massive than the sun

PASADENA, Calif.—Discoveries of new planets just keep coming and coming. Take, for instance, the 18 recently found by a team of astronomers led by scientists at the California Institute of Technology (Caltech).

"It's the largest single announcement of planets in orbit around stars more massive than the sun, aside from the discoveries made by the Kepler mission," says John Johnson, assistant professor of astronomy at Caltech and the first author on the team's paper, which was published in the December issue of The Astrophysical Journal Supplement Series. The Kepler mission is a space telescope that has so far identified more than 1,200 possible planets, though the majority of those have not yet been confirmed.

Using the Keck Observatory in Hawaii—with follow-up observations using the McDonald and Fairborn Observatories in Texas and Arizona, respectively—the researchers surveyed about 300 stars. They focused on those dubbed "retired" A-type stars that are more than one and a half times more massive than the sun. These stars are just past the main stage of their life—hence, "retired"—and are now puffing up into what's called a subgiant star.

To look for planets, the astronomers searched for stars of this type that wobble, which could be caused by the gravitational tug of an orbiting planet. By searching the wobbly stars' spectra for Doppler shifts—the lengthening and contracting of wavelengths due to motion away from and toward the observer—the team found 18 planets with masses similar to Jupiter's.

This new bounty marks a 50 percent increase in the number of known planets orbiting massive stars and, according to Johnson, provides an invaluable population of planetary systems for understanding how planets—and our own solar system—might form. The researchers say that the findings also lend further support to the theory that planets grow from seed particles that accumulate gas and dust in a disk surrounding a newborn star.

According to this theory, tiny particles start to clump together, eventually snowballing into a planet. If this is the true sequence of events, the characteristics of the resulting planetary system—such as the number and size of the planets, or their orbital shapes—will depend on the mass of the star. For instance, a more massive star would mean a bigger disk, which in turn would mean more material to produce a greater number of giant planets.

In another theory, planets form when large amounts of gas and dust in the disk spontaneously collapse into big, dense clumps that then become planets. But in this picture, it turns out that the mass of the star doesn't affect the kinds of planets that are produced.

So far, as the number of discovered planets has grown, astronomers are finding that stellar mass does seem to be important in determining the prevalence of giant planets. The newly discovered planets further support this pattern—and are therefore consistent with the first theory, the one stating that planets are born from seed particles.

"It's nice to see all these converging lines of evidence pointing toward one class of formation mechanisms," Johnson says.

There's another interesting twist, he adds: "Not only do we find Jupiter-like planets more frequently around massive stars, but we find them in wider orbits." If you took a sample of 18 planets around sunlike stars, he explains, half of them would orbit close to their stars. But in the cases of the new planets, all are farther away, at least 0.7 astronomical units from their stars. (One astronomical unit, or AU, is the distance from Earth to the sun.)

In systems with sunlike stars, gas giants like Jupiter acquire close orbits when they migrate toward their stars. According to theories of planet formation, gas giants could only have formed far from their stars, where it's cold enough for their constituent gases and ices to exist. So for gas giants to orbit nearer to their stars, certain gravitational interactions have to take place to pull these planets in. Then, some other mechanism—perhaps the star's magnetic field—has to kick in to stop them from spiraling into a fiery death.

The question, Johnson says, is why this doesn't seem to happen with so-called hot Jupiters orbiting massive stars, and whether that dearth is due to nature or nurture. In the nature explanation, Jupiter-like planets that orbit massive stars just wouldn't ever migrate inward. In the nurture interpretation, the planets would move in, but there would be nothing to prevent them from plunging into their stars. Or perhaps the stars evolve and swell up, consuming their planets. Which is the case? According to Johnson, subgiants like the A stars they were looking at in this paper simply don't expand enough to gobble up hot Jupiters. So unless A stars have some unique characteristic that would prevent them from stopping migrating planets—such as a lack of a magnetic field early in their lives—it looks like the nature explanation is the more plausible one.

The new batch of planets have yet another interesting pattern: their orbits are mainly circular, while planets around sunlike stars span a wide range of circular to elliptical paths. Johnson says he's now trying to find an explanation.

For Johnson, these discoveries have been a long time coming. This latest find, for instance, comes from an astronomical survey that he started while a graduate student; because these planets have wide orbits, they can take a couple of years to make a single revolution, meaning that it can also take quite a few years before their stars' periodic wobbles become apparent to an observer. Now, the discoveries are finally coming in. "I liken it to a garden—you plant the seeds and put a lot of work into it," he says. "Then, a decade in, your garden is big and flourishing. That's where I am right now. My garden is full of these big, bright, juicy tomatoes—these Jupiter-sized planets."

The other authors on the The Astrophysical Journal Supplement Series paper, "Retired A stars and their companions VII. Eighteen new Jovian planets," include former Caltech undergraduate Christian Clanton, who graduated in 2010; Caltech postdoctoral scholar Justin Crepp; and nine others from the Institute for Astronomy at the University of Hawaii; the University of California, Berkeley; the Center of Excellence in Information Systems at Tennessee State University; the McDonald Observatory at the University of Texas, Austin; and the Pennsylvania State University. The research was supported by the National Science Foundation and NASA.

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Caltech Ranked First in Physical Sciences

Caltech's physical-sciences program is number one among world universities in this year's Times Higher Education rankings, sharing the top spot with Princeton.

"We're pleased that Caltech is recognized as one of the world's best universities in the physical sciences," says Tom Soifer, chair of the Division of Physics, Math and Astronomy. "We take great pride in our research and in educating the world's leading scientists of the future."

Last year, Caltech's physical-sciences program was second to Harvard. This year, Harvard drops to sixth while UC Berkeley, MIT, and Stanford fill out the top five. Times Higher Education has also listed Caltech as the top university in the world and has placed Caltech's engineering and technology program first.

In addition to physical sciences and engineering and technology, Times Higher Education World University Rankings 2011–2012 ranks four other subjects: arts and humanities; clinical, preclinical, and health; life sciences; and social sciences. Out of the top 50 physical-sciences programs, 27 are in the United States.

The rankings are based on data compiled by Thomson Reuters. For the complete list of the world's top 50 physical sciences-programs—as well as the rest of the rankings and all the performance indicators—go to the Times Higher Education website.

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Particles and Pants

New Faculty Join PMA

Ryan Patterson is no stranger to Caltech. As an undergraduate, the Mississippi native studied physics, devoting a good part of his last two years to doing research with Professor of Physics Brad Filippone, building an electron gun to help calibrate an experiment that analyzed the decay of ultracold neutrons. "It was a lot of fun," Patterson recalls.

After graduating in 2000, Patterson got his PhD in physics at Princeton, where he studied the elusive neutrino, a nearly massless particle that zips around at almost the speed of light. He returned to Caltech as a postdoctoral scholar in 2007, and, in 2010, joined the faculty of the Division of Physics, Mathematics and Astronomy as an assistant professor. His work and day-to-day life as a professor at Caltech is an entirely new experience, he says: "It's completely different. It doesn't even really feel like the same place."

Patterson's research focuses on the mysterious nature of the neutrino. Produced in nuclear reactions—such as in stars or in nuclear power plants—neutrinos hardly interact with anything. In fact, billions of them are harmlessly surging through your body this very second.

Most of Patterson's attention is now centered on NOvA, a new neutrino experiment that's scheduled to start running in 2013. NOvA will measure so-called muon neutrinos that are being produced at Fermilab near Chicago. One of its main goals is to learn if the muon neutrinos are turning into another type called electron neutrinos. Measuring how many of these transformations take place—if at all—will help physicists determine a parameter called the mixing angle. Knowing this number is key to some of the big fundamental questions in physics, such as why the universe is full of matter instead of antimatter.

According to current theory, the big bang should have created equal amounts of matter and antimatter. But when the two interact, they annihilate each other and produce energy, meaning that stars, planets, and us—all made out of ordinary matter—shouldn't exist. And since we do exist, there somehow must have been a bit more matter than antimatter at the beginning. "We should've all been annihilated at the beginning of the universe," Patterson says. "Neutrinos may hold the key as to why that asymmetry is there, and we're trying to understand that."


Vladimir Markovic comes to Caltech from the University of Warwick, where he was on the mathematics faculty for 10 years. He also spent time as an associate professor at SUNY Stony Brook. Having just arrived in Pasadena in August, the professor of mathematics is the newest member of the PMA faculty.

Markovic studies the shapes and structures of mathematical spaces called manifolds. (For example, a line is a one-dimensional manifold while a plane is a two-dimensional one.) For the mathematically minded, he's an expert in low-dimensional geometry and Teichmüller theory. In particular, he has worked with something called the "good pants homology," which involves a mathematical object with three holes that has the same topological properties as a pair of pants, which has a hole for the waist and two for the legs. He combines these structures, mathematically stitching the pants together at their holes to create new structures. For example, attaching two pairs of pants at their waists would result in a new structure with four holes (the four legs). "You can say that what I do for a living is gluing pants," Markovic quips. Gluing more and more pants together produces increasingly complicated surfaces, and his goal is to understand the properties of those surfaces.

Born in Germany, Markovic studied mathematics at the University of Belgrade, receiving his PhD in 1998. Math was one of his two passions in school; soccer was the other. Mathematics, he says, is also about competition—it's about seeking new challenges in much the same way that mountain climbers want to scale higher and higher peaks. "I like solving problems. It's really the big draw for me, and it's still what excites me."

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Oceans of Water in a Planet-Forming Disk

Astronomers have detected massive quantities of water in a planet-forming gas disk around a young star. The water—which is frozen in the icy outer regions of the disk—could fill Earth's oceans several thousand times over. The discovery, published in the October 21 issue of the journal Science, could help explain how Earth got its oceans and suggests that our planet may not be the only watery world in the cosmos.

"This new result shows that the reservoir of water ice in such a disk is huge," says Darek Lis, a senior research associate in physics at Caltech and a coauthor on the paper. If other planet-forming disks also have such copious amounts of water, then there's a greater chance that other planets are also wet. "Water-covered planets like Earth may be quite common," he says.

To make the discovery, the team of researchers, which includes Caltech professor of planetary science Geoff Blake and JPL's John Pearson, pointed the Herschel Space Observatory at a star called TW Hydrae, located 175 light years away. TW Hydrae, which is only about 10 million years old, is surrounded by a disk of gas—just as the young sun was about 4.6 billion years ago.

The team found the water vapor—which previously had never been detected in the outer regions of such a disk—using Herschel's Heterodyne Instrument for the Far Infrared (HIFI). The vapor, the researchers say, likely is produced when ultraviolet light from the central and other nearby stars bombards large reservoirs of ice in the disk.

Lis, Blake, and colleagues estimate that the disk holds several thousand oceans' worth of water ice. The fact that there's so much water in this embryonic planetary system means that the outer part of the solar nebula—the gas disk that formed our solar system—could have been chock-full of ice as well. Such a large source of water was crucial for the creation of Earth's seas. According to the current theory of solar-system formation, water was scarce in the inner part of solar nebula, where Earth formed about 4.5 billion years ago. "Water is essential to life as we know it," Blake says. "But the early Earth is predicted to have been hot and dry." Earth's water, then, must have come from somewhere else. One likely source? Comets.

Comets, often called dirty snowballs, are chunks of ice and rock that orbit the sun in long, swooping trajectories. Because they spend most of their time in the frigid outer-edges of the solar system, comets can contain prodigious quantities of water ice, and collisions of a few million comets with Earth could have brought enough water to create the oceans. A few million comets may sound like a lot, but there was a tremendous amount of debris flying around back then, and with possibly as many as trillions of icy objects in the outer solar system, the researchers explain, only a tiny fraction would have needed to hit Earth.

If this story is true, ample water should exist in the outer disk where comets form—which is exactly what the astronomers just discovered in TW Hydrae. "These results beautifully confirm the notion that the critical reservoir of ice in forming planetary systems lies well outside the formation zone of Earthlike planets," Blake says.

The TW Hydrae measurements come on the heels of the discovery that the chemical signature of water ice in comet Hartley 2 is similar to the signature of Earth's oceans, published online on October 5 in the journal Nature. In the Nature paper, Lis and Blake, along with Caltech postdoctoral scholar Martin Emprechtinger, measured the ratio of deuterium (an isotope of hydrogen with an extra neutron in its nucleus) to regular hydrogen in water ice evaporated from Hartley 2. The ratio was very similar to the ratios in Earth's ocean water, supporting the idea that the seas did come from the skies.

Previous measurements of the composition of ice in other comets revealed chemical signatures different from those of our oceans, suggesting that Earth got most of its water from asteroids. These other comets, however, were from the Oort cloud, a distant collection of up to trillions of icy bodies enveloping the entire solar system. Hartley 2 comes from the Kuiper Belt, a belt of objects at the edge of the solar system. Therefore, Lis says, "icy bodies in the outer solar system—the Kuiper Belt—could have been the source of Earth's water. These findings are yet another important step in our quest to understand the origin of life on Earth and assess possibilities of life in other planetary systems."

To read more, see the JPL press releases on TW Hydrae and comet Hartley 2.

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Thorne Selected to Receive Graduate Education Award

Kip Thorne, Caltech's Feynman Professor of Theoretical Physics, Emeritus, has been selected to receive the 2012 John David Jackson Excellence in Graduate Physics Education Award from the American Association of Physics Teachers (AAPT).

Thorne has won many awards over the years—including the 1996 Lilienfeld Prize of the American Physical Society, the 2004 California Scientist of the Year, and a 2010 UNESCO Niels Bohr Gold Medal—in recognition of his contributions to the current understanding of black holes and gravitational waves.  The Jackson Award recognizes another aspect of his career: his contributions as a teacher and mentor. 

Thorne has been recognized previously for the role he has played in the education of young scientists—in 2000, he won an ASCIT (Associated Students of Caltech) award for his teaching of undergraduates, and in 2004, he was honored with the Caltech Graduate Student Council Mentoring Award.

According to a statement prepared by the AAPT, "Thorne has been mentor and thesis advisor for more than 50 Ph.D. physicists who have gone on to become world leaders in their chosen fields of research and teaching. A list of current leaders in relativity, gravitational waves, relativistic astrophysics, and even quantum information theory, would be heavily populated by former graduate students of Kip Thorne, together with other students who took his courses and were inspired and enabled by them."

For his part, Thorne says, "More than anything else, the thing that kept me at Caltech throughout my career was our superb graduate students and postdocs.  I have learned more from them over the years than they have learned from me.  I am grateful to them for the role they played in nominating me for this award."

In their letter of nomination, a group of Thorne's former students wrote, "Graduate physics education is under-appreciated and often neglected. We hope that the new AAPT Jackson award, and its acknowledgment of great teachers and textbook writers, like Kip, will inspire others to follow in his footsteps. We know of no one who has worked harder on his teaching and his textbooks, and with greater resulting effect, than our beloved teacher, Kip Thorne."

Thorne earned his BS from Caltech in 1962 and his PhD from Princeton University in 1965. He joined the Caltech faculty in 1966 and was promoted to emeritus status in 2009.

Thorne will receive the award in February at the 2012 AAPT Winter Meeting in Ontario, California. 

To read the full release from the AAPT, click here.

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Caltech Awarded $12.6 Million for New Institute for Quantum Information and Matter

PASADENA, Calif.—The California Institute of Technology (Caltech) has been awarded $12.6 million in funding over the next five years by the National Science Foundation (NSF) to create a new Physics Frontiers Center. Dubbed the Institute for Quantum Information and Matter (IQIM), the center will bring physicists and computer scientists together to push theoretical and experimental boundaries in the study of exotic quantum states.

Every three years, the NSF selects new Physics Frontier Centers for funding based on their potential for transformational advances in the most promising research areas at the intellectual frontiers of physics. Caltech's IQIM was chosen for funding from more than 50 proposals this year. 

The NSF's decision to fund the IQIM leverages the groundwork done by the Center for Exotic Quantum Systems (CEQS), a program funded by the Gordon and Betty Moore Foundation, as well as an earlier NSF-sponsored Institute for Quantum Information (IQI). With the support of the NSF and the Moore Foundation, the new Physics Frontiers Center, CEQS, and IQI will be merged into a single entity—the Institute for Quantum Information and Matter.

"The unrestricted funds provided by the Moore Foundation had a dramatic effect on the decision to fund this Physics Frontiers Center," says Caltech president Jean-Lou Chameau. "That discretionary funding allowed the provost to provide seed money to what might otherwise have been considered a somewhat risky, unconventional field of study. Now, it is one of our most exciting and rapidly growing research initiatives."

Fundamental particles at the atomic level behave according to the laws of quantum physics, which in many respects defy common sense. At this level, individual particles of a composite system can become strongly correlated, or entangled, in such a way that they maintain their relation to one another no matter where they exist in the universe. Such quantum entanglement can endow a system with astonishing properties.

The IQIM will bring together Caltech's established theoretical programs and analytic tools for studying the quantum realm with emerging laboratory capabilities that will allow scientists to delve deeper into quantum entanglement and the unimagined behaviors it may yield. The research is aimed at making advances in basic physics, as well as helping to provide scientific foundations for designing materials with remarkable properties; additionally, this work may eventually help point the way to a quantum computer capable of solving problems that today's digital computers could never handle.

"My colleagues and I believe that an exciting frontier of 21st-century science is the exploration of the surprising phenomena that can arise in highly entangled quantum systems," says H. Jeff Kimble, the William L. Valentine Professor and professor of physics at Caltech, who will direct the IQIM. "The IQIM will provide a sustaining base for our efforts to discover new principles and phenomena at this entanglement frontier."

In addition to Kimble, the Institute for Quantum Information and Matter will be led by three codirectors: Jim Eisenstein, the current director of CEQS and the Frank J. Roshek Professor of Physics and Applied Physics; Oskar Painter, professor of applied physics and executive officer for applied physics and materials science; and John Preskill, the current director of the IQI and the Richard P. Feynman Professor of Theoretical Physics.

Studies of quantum entanglement and its applications are necessarily multidisciplinary in nature. Therefore, the 16 Caltech faculty members who will make up the core of the new center are drawn from such disciplines as physics, applied physics, and computer science. The newly renovated historic Norman Bridge Laboratory of Physics and the IQI's home base in the Annenberg Center for Information Science and Technology will serve as two central hubs for IQIM faculty on campus.

"When you bring innovative scientists and engineers together and provide them with the facilities and collaborative spaces they need, magic happens. The magic involves transforming the way we think about and impact our world," says Ares Rosakis, chair of the Division of Engineering and Applied Science (EAS) at Caltech. "I am delighted that an initial collaboration beginning in 2000 between the Division of Engineering and Applied Science (EAS) and the Division of Physics, Mathematics and Astronomy (PMA)—the Institute of Quantum Information (IQI)—planted the seeds for this new NSF institute at Caltech."

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Caltech Named World's Top University in New Times Higher Education Global Ranking

PASADENA, Calif.—The California Institute of Technology (Caltech) has been rated the world's number one university in the 2011–2012 Times Higher Education global ranking of the top 200 universities, displacing Harvard University from the top spot for the first time in the survey's eight-year history.

Caltech was number two in the 2010–2011 ranking; Harvard and Stanford University share the second spot in the 2011–2012 survey, while the University of Oxford and Princeton University round out the top five.

"It's gratifying to be recognized for the work we do here and the impact it has—both on our students and on the global community," says Caltech president Jean-Lou Chameau. "Today's announcement reinforces Caltech's legacy of innovation, and our unwavering dedication to giving our extraordinary people the environment and resources with which to pursue their best ideas. It's also truly gratifying to see three California schools—including my alma mater, Stanford—in the top ten."

Thirteen performance indicators representing research (worth 30% of a school's overall ranking score), teaching (30%), citations (30%), international outlook (which includes the total numbers of international students and faculty and the ratio of scholarly papers with international collaborators; 7.5%), and industry income (a measure of innovation; 2.5%) are included in the data. Among the measures included are a reputation survey of 17,500 academics; institutional, industry, and faculty research income; and an analysis of 50 million scholarly papers to determine the average number of citations per scholarly paper, a measure of research impact.

"We know that innovation is the driver of the global economy, and is especially important during times of economic volatility," says Kent Kresa, chairman of the Caltech Board of Trustees. "I am pleased that Caltech is being recognized for its leadership and impact; this just confirms what many of us have known for a long time about this extraordinary place."

"Caltech has been one of California's best-kept secrets for a long time," says Caltech trustee Narendra Gupta. "But I think the secret is out!"

Times Higher Education, which compiled the listing using data supplied by Thomson Reuters, reports that this year's methodology was refined to ensure that universities with particular strength in the arts, humanities, and social sciences are placed on a more equal footing with those with a specialty in science subjects. Caltech—described in a Times Higher Education press release as "much younger, smaller, and specialised" than Harvard—was nevertheless ranked the highest based on their metrics.

According to Phil Baty, editor of the Times Higher Education World University Rankings, "the differences at the top of the university rankings are miniscule, but Caltech just pips Harvard with marginally better scores for 'research—volume, income, and reputation,' research influence, and the income it attracts from industry. With differentials so slight, a simple factor plays a decisive role in determining rank order: money."

"Harvard reported funding increases similar in proportion to other institutions, whereas Caltech reported a steep rise (16%) in research funding and an increase in total institutional income," Baty says.

Data for the Times Higher Education's World University Rankings was provided by Thomson Reuters from its Global Institutional Profiles Project (http://science.thomsonreuters.com/globalprofilesproject/), an ongoing, multistage process to collect and validate factual data about academic institutional performance across a variety of aspects and multiple disciplines.

For a full list of the world's top 200 schools and all of the performance indicators, go to http://www.timeshighereducation.co.uk/world-university-rankings/.

# # # 

The California Institute of Technology (Caltech) is a small, private university in Pasadena that conducts instruction and research in science and engineering, with a student body of about 900 undergraduates and 1,200 graduate students. Recognized for its outstanding faculty, including several Nobel laureates, and such renowned off-campus facilities as the Jet Propulsion Laboratory, the W. M. Keck Observatory, and the Palomar Observatory, Caltech is one of the world's preeminent research centers.

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Astronomers Discover a Black Hole Ripping a Star Apart

Astronomers have discovered a supermassive black hole tearing a star to shreds. In late March, NASA's Swift satellite detected flares of X rays and gamma rays from a mysterious source about 3.9 billion light years away. To follow up on the strange signal, astronomers used the 40-meter dish at Caltech's Owens Valley Radio Observatory (OVRO), the Combined Array for Research in Millimeter-wave Astronomy (CARMA)—of which Caltech is a member institution—and other telescopes that observe in centimeter, millimeter, and radio wavelengths. The subsequent data showed that the source is most likely a star being ripped apart by a black hole millions of times more massive than the sun.

"This is a remarkable discovery," says John Carpenter, a senior research associate in astronomy at Caltech and executive director of OVRO. "We are likely witnessing the birth of a jet as a stray star is ripped apart by a massive black hole." The astronomers describe their results in the August 25 issue of the journal Nature.

When the stellar shreds spiral in toward the black hole, which sits at the center of a galaxy, they heat up and produce powerful jets of particles that stream out at nearly the speed of light. Astronomers have predicted that these violent events could happen, and they've seen them before, but only as bright flares in optical, ultraviolet, and X-ray wavelengths.

"When I first saw the CARMA detection, I literally fell out of my chair," says Ashley Zauderer, an astronomer at the Harvard-Smithsonian Center for Astrophysics who led the team. The astronomers say that this is the first time such a scenario—called a tidal disruption event—has been observed at radio wavelengths, suggesting that scanning the skies for similar radio signals could be a fruitful way to find more stars being devoured by a black hole.

In addition to Carpenter, the Caltech researchers on the team are Shri Kulkarni, John D. and Catherine T. MacArthur Professor of Astronomy and Planetary Sciences; graduate students Kunal Mooley, Walter Max-Moerbeck, and Joseph Richards; Nikolaus Volgenau, CARMA assistant director of operations; Tony Readhead, Barbara and Stanley Rawn, Jr., Professor of Astronomy and director of OVRO; and staff scientist Martin Shepherd.

To read more and to watch an animated video, click here.

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New LIGO Executive Director Named

PASADENA, Calif.—David Reitze has been named executive director of the Laser Interferometer Gravitational-Wave Observatory (LIGO), designed and operated by the California Institute of Technology (Caltech) and the Massachusetts Institute of Technology (MIT), with funding from the National Science Foundation (NSF). Reitze has also been named a senior research associate at Caltech.

A professor of physics at the University of Florida, Gainesville, and a visiting associate at Caltech since 2007, Reitze will succeed the retiring Jay Marx. Marx, a senior research associate in physics at Caltech, served as executive director since 2006 and will continue to work on LIGO part-time.

"I'm really excited about joining the LIGO laboratory and Caltech and serving in the role of executive director," says Reitze, who received his PhD from the University of Texas at Austin in 1990 and has been involved in the LIGO project since 1996. His early research focused on ultrafast optics and the development of high-power optical components and ultrafast lasers. More recently, he led the design effort for the input optics of Advanced LIGO, a more sensitive incarnation of the detector slated to begin operation in 2014. "In addition to the incredible science that LIGO will do, one of the main reasons I accepted the position was the outstanding quality and commitment of the LIGO laboratory staff," he says.

LIGO was originally proposed decades ago as a means of detecting gravitational waves. Gravitational waves are ripples in the fabric of space and time—produced by massive accelerating objects such as black-hole and neutron-star collisions—which propagate outward through the universe. They were first predicted in 1916 as a consequence of Albert Einstein's general theory of relativity.

Each of the L-shaped LIGO interferometers (including 4-km detectors in Hanford, Washington, and Livingston, Louisiana) use a laser split into two beams that travel back and forth down long arms (which are beam tubes from which the air has been evacuated). The beams are used to monitor the distance between precisely configured mirrors. According to Einstein's theory, the relative distance between the mirrors will change very slightly when a gravitational wave passes by. 

LIGO research is carried out by the LIGO Scientific Collaboration (LSC), a group of 840 scientists at universities around the United States and in 13 other countries; Reitze served as the LSC spokesperson from 2007 to 2011.

The LSC network includes the LIGO interferometers and the GEO600 interferometer, a project located near Hannover, Germany, and designed and operated by scientists from the Max Planck Institute for Gravitational Physics, along with partners in the United Kingdom funded by the Science and Technology Facilities Council (STFC). The LSC works jointly with the Virgo Collaboration—which designed and constructed the 3-km long Virgo interferometer located in Cascina, Italy—to analyze data from the LIGO, GEO, and Virgo interferometers.

The next major milestone for LIGO is Advanced LIGO, which will incorporate upgraded designs and technologies that have been developed by the LSC. The original configuration of LIGO was sensitive enough to detect a change in the lengths of the 4-km arms by a distance one-thousandth the size of a proton; Advanced LIGO, which will utilize the infrastructure of LIGO, will be 10 times more sensitive.

The increased sensitivity will be important because it will allow scientists to detect cataclysmic events such as black-hole and neutron-star collisions at 10-times-greater distances. And because LIGO can "see" in all directions, Advanced LIGO will be 1,000 times more likely to detect gravitational waves and will make important contributions to astronomy and physics.

"This is a great time in LIGO's history," Reitze says. "Over the past decade, we've demonstrated that we can build and operate the LIGO interferometers with truly exquisite sensitivity and use them to conduct scientifically interesting searches for gravitational waves. It's also an exciting time for worldwide gravitational-wave scientific community," he adds.

"We're really delighted to have Dr. Reitze take over the leadership of LIGO. He knows the project, the science, and the challenges, and is superbly qualified to lead the team in bringing the Advanced LIGO detector on line," says Tom Soifer, professor of physics, director of the Spitzer Science Center, and chair of the Division of Physics, Mathematics and Astronomy at Caltech. "Jay Marx set a high standard," he adds, "and Dave is fully ready to match that in leading LIGO in this most exciting time. We're looking forward to the first detections of gravitational waves from astronomical sources, and the new window on the universe it will provide."

"Once Advanced LIGO is running, we'll continue to work closely with our European colleagues at GEO600 and Virgo as part of the new and growing global gravitational-wave network," Reitze says. "The Large Cryogenic Gravitational Wave Telescope in Japan is scheduled to begin operation soon after Advanced LIGO, adding a fourth detector to the network. The global network will allow us to look at the underlying sources of gravitational waves in tandem with other types of astronomical telescopes—optical, radio, X-ray, gamma ray—to give a much better picture of the astrophysics of the most violent events in the universe."

Writer: 
Kathy Svitil
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