From One Collapsing Star, Two Black Holes Form and Fuse

Black holes—massive objects in space with gravitational forces so strong that not even light can escape them—come in a variety of sizes. On the smaller end of the scale are the stellar-mass black holes that are formed during the deaths of stars. At the larger end are supermassive black holes, which contain up to one billion times the mass of our sun. Over billions of years, small black holes can slowly grow into the supermassive variety by taking on mass from their surroundings and also by merging with other black holes. But this slow process can't explain the problem of supermassive black holes existing in the early universe—such black holes would have formed less than one billion years after the Big Bang.

Now new findings by researchers at the California Institute of Technology (Caltech) may help to test a model that solves this problem.

Certain models of supermassive black hole growth invoke the presence of "seed" black holes that result from the deaths of very early stars. These seed black holes gain mass and increase in size by picking up the materials around them—a process called accretion—or by merging with other black holes. "But in these previous models, there was simply not enough time for any black hole to reach a supermassive scale so soon after the birth of the universe," says Christian Reisswig, NASA Einstein Postdoctoral Fellow in Astrophysics at Caltech and the lead author of the study. "The growth of black holes to supermassive scales in the young universe seems only possible if the 'seed' mass of the collapsing object was already sufficiently large," he says.

To investigate the origins of young supermassive black holes, Reisswig, in collaboration with Christian Ott, assistant professor of theoretical astrophysics, and their colleagues turned to a model involving supermassive stars. These giant, rather exotic stars are hypothesized to have existed for just a brief time in the early universe. Unlike ordinary stars, supermassive stars are stabilized against gravity mostly by their own photon radiation. In a very massive star, photon radiation—the outward flux of photons that is generated due to the star's very high interior temperatures—pushes gas from the star outward in opposition to the gravitational force that pulls the gas back in. When the two forces are equal, this balance is called hydrostatic equilibrium.

During its life, a supermassive star slowly cools due to energy loss through the emission of photon radiation. As the star cools, it becomes more compact, and its central density slowly increases. This process lasts for a couple of million years until the star has reached sufficient compactness for gravitational instability to set in and for the star to start collapsing gravitationally, Reisswig says.

Previous studies predicted that when supermassive stars collapse, they maintain a spherical shape that possibly becomes flattened due to rapid rotation. This shape is called an axisymmetric configuration. Incorporating the fact that very rapidly spinning stars are prone to tiny perturbations, Reisswig and his colleagues predicted that these perturbations could cause the stars to deviate into non-axisymmetric shapes during the collapse. Such initially tiny perturbations would grow rapidly, ultimately causing the gas inside the collapsing star to clump and to form high-density fragments.

These fragments would orbit the center of the star and become increasingly dense as they picked up matter during the collapse; they would also increase in temperature. And then, Reisswig says, "an interesting effect kicks in." At sufficiently high temperatures, there would be enough energy available to match up electrons and their antiparticles, or positrons, into what are known as electron-positron pairs. The creation of electron-positron pairs would cause a loss of pressure, further accelerating the collapse; as a result, the two orbiting fragments would ultimately become so dense that a black hole could form at each clump. The pair of black holes might then spiral around one another before merging to become one large black hole. "This is a new finding," Reisswig says. "Nobody has ever predicted that a single collapsing star could produce a pair of black holes that then merge."

Reisswig and his colleagues used supercomputers to simulate a supermassive star that is on the verge of collapse. The simulation was visualized with a video made by combining millions of points representing numerical data about density, gravitational fields, and other properties of the gases that make up the collapsing stars.

Although the study involved computer simulations and is thus purely theoretical, in practice, the formation and merger of pairs of black holes can give rise to tremendously powerful gravitational radiation—ripples in the fabric of space and time, traveling at the speed of light—that is likely to be visible at the edge of our universe, Reisswig says. Ground-based observatories such as the Laser Interferometer Gravitational-Wave Observatory (LIGO), comanaged by Caltech, are searching for signs of this gravitational radiation, which was first predicted by Albert Einstein in his general theory of relativity; future space-borne gravitational-wave observatories, Reisswig says, will be necessary to detect the types of gravitational waves that would confirm these recent findings.

Ott says that these findings will have important implications for cosmology. "The emitted gravitational-wave signal and its potential detection will inform researchers about the formation process of the first supermassive black holes in the still very young universe, and may settle some—and raise new—important questions on the history of our universe," he says.

These findings were published in Physical Review Letters the week of October 11 in a paper titled "Formation and Coalescence of Cosmological Supermassive-Black-Hole Binaries in Supermassive-Star Collapse." Caltech coauthors authors on the study include Ernazar Abdikamalov, Roland Haas, Philipp Mösta. Another coauthor on the study, Erik Schnetter, is at the Perimeter Institute for Theoretical Physics in Canada. The work was funded by the National Science Foundation, NASA, the Alfred P. Sloan Foundation, and the Sherman Fairchild Foundation.

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qCraft Introduces Gaming Kids to Quantum Principles

Finding common ground between schoolchildren and quantum-mechanics researchers is no easy task. After all, understanding quantum mechanics—the physics that governs the behavior of matter and light at the atomic (and subatomic) scale—can be daunting even for some physicists. However, through a recent collaboration with Google, researchers at Caltech have created a new space for this unlikely interaction—in the world of Minecraft, a popular video game.

The project originated five months ago, when Spyridon Michalakis, a staff researcher at Caltech's Institute for Quantum Information and Matter (IQIM), received a phone call from Google Creative Lab executive producer Lorraine Yurshansky. Yurshansky was calling about making a promotional video for Google's recent collaboration with NASA and the Universities Space Research Association on the development of the Quantum Artificial Intelligence Lab. The collaborators hope that the new lab, hosted at NASA Ames Research Center, will harness the power of quantum computing—next-generation computing technologies that are rooted in the principles of quantum mechanics—in order to solve currently intractable problems in machine learning and optimization. During their conversation, Michalakis, who is also the outreach manager at IQIM, brought up educational outreach as a way to invest in the future of quantum computing.

"To me, more important than telling kids and the public what we've accomplished already is to tell them of all of the exciting things that have yet to be discovered but will be discovered—by them. In the end, I think that is the point of educational outreach. It is not just to brag about what we've done in academia or to get research funding," Michalakis explains. "We're trying to get kids excited about the future, and I thought Google's other educational involvement with STEM outreach and the maker movement was a good example of this. "

The technology giant quickly got on board. A few weeks after the initial phone call, Michalakis was approached again by Google Creative Lab, which had a proposal for IQIM: come up with a way to use Minecraft to get kids excited about quantum mechanics and quantum computing.

"At first, I did not know what Minecraft was," recalls Michalakis about his first introduction to the video game. "But then I saw it, and I thought, 'This is huge! It's everywhere!'"

In Minecraft, which has been downloaded more than 30 million times worldwide, players can freely build and create their own world by mining and stacking different types of bricks in a sandbox-like environment. Because of its customizable dynamic, the game has also become a background platform for many user-generated modifications, or "mods," that add novel capabilities, brick textures, and properties to the original Minecraft game.

Partnering with the creators of MinecraftEdu—the educational arm of Minecraft—Michalakis and game developers from E-Line Media developed a new mod, produced and funded by Google, to introduce quantum mechanics into the game's landscape.

The mod, dubbed qCraft, was unveiled for download on October 15. Although the project was completed in just a few months, Michalakis found that striking a balance between quantum learning and a fun gameplay experience was challenging because the general elements of the classic Minecraft game obey the laws of classical mechanics—the rules that govern the behaviors of larger objects, like molecules, grains of sand, and even humans. "I had to think, How do I bring quantum mechanics into the classical world of Minecraft?" Michalakis says. "I struggled with it because I wanted to recreate quantum mechanics as faithfully as possible."

qCraft uses the Minecraft platform to introduce three high-level quantum-mechanical concepts: observational dependency, superposition, and entanglement. The mod informally teaches players about observational dependency by allowing them to create either quantum blocks or "observer dependent blocks" (ODBs)—which are classical, but have some quantum-like behaviors. ODBs, Michalakis says, are like rolled dice: if you roll a six, there are six dots on the top face, and the only way this number "changes" is if you look at the die from the bottom or a side, where you will see a different, but fixed, number. Instead of numbers, boxes in qCraft can have different materials on each face, such as diamond or gold.

Using this first concept as a starting point, players can learn more about the vagaries of the quantum universe and how it differs from the classical one by observing in the quantum blocks a phenomenon known as superposition. Superposition is the principle that allows particles to occupy more than one state at the same time (and that permits Schrödinger's notorious cat to be simultaneously dead and alive). "In quantum objects, things behave differently. If you were to roll a six on a quantum die, the number on the face of the die will still be a six. But if you now look from the side, you will not always see a three where a three was supposed to be—you will sometimes see a three and sometimes a four, and you will never be able to predict which one will show up," Michalakis says. Superposition in qCraft means that one face of a quantum block could be gold at first glance, but after looking at another face and then coming back for a second glance, that same face is just as likely to be diamond as it is to be gold—or to completely disappear.

Additionally, the quantum blocks in one qCraft world can be "entangled" with the blocks in another qCraft world, allowing them to share information and to influence each other, despite having no visible connection. Such entanglement allows a player to make one quantum block disappear—and in the process make a group of quantum wall blocks disappear to create a doorway. Entanglement (which Albert Einstein called "spooky action at a distance") may not be possible in the classical world, but researchers at IQIM and around the world, through their experiments, are trying to scale up the weirdness of the quantum world, pushing the boundaries between our classical intuition and the strange and profound properties of quantum-mechanical objects. It is a herculean effort, Michalakis notes, all the more difficult because of the fragile nature of information at the quantum level, which tends to rapidly "decohere" into its classical counterparts due to interactions with its surrounding environment, the ever-present observer.

To deal with these environmental interactions, a feature of the mod even allows players to wear "quantum goggles" so that they can hide their role as an observer, leaving the fate of the quantum blocks unresolved.

Michalakis will provide more insight into how the behaviors of these modified Minecraft blocks relate to quantum mechanics in a series of blog posts on the qCraft website. "Through the game and the blog posts, we hope to bring the public up to speed on some of the most fascinating physics research that is happening right now, including studies of quantum mechanics, black holes, time travel, wormholes, and more," he says.

The outreach plan for qCraft doesn't end there. In November, Michalakis, along with the qCraft team and the Caltech graduate and undergraduate students who helped him to build and beta-test the mod, will attend Minecon 2013, an annual convention for Minecraft players, developers, and enthusiasts. At the meeting, the team will promote the mod, explain concepts, and answer questions from current qCraft users.

The mod is already gathering a fan base, but Michalakis says the final success will be when players start to dig deeper and begin to learn about the equations and concepts that are its foundation. Indeed, Michalakis hopes that qCraft will encourage many future scientists to "look under the hood" of quantum mechanics. "We're the table upon which they can build something bigger. We're not the end," he says.

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Building the World's Most Sensitive Detectors: A Conversation with Rana Adhikari

Caltech professor of physics Rana Adhikari has been on a singular quest for 15 years: to detect gravitational waves.

Gravitational waves—ripples in the fabric of space-time—are predicted by Einstein's theory of general relativity. Major astrophysical events such as the collapse of a binary system of neutron stars or black holes or one of each should release intense gravitational waves in the frequency range that we potentially might detect here on Earth. As theorized, gravitational waves are curious things; they move across the universe at the speed of light and pass right through everything they encounter without being affected as electromagnetic waves (such as light and radio waves) would be. And yet they are very weak compared to electromagnetic waves.

Scientists began to search for gravitational waves at the end of the 1960s, trying out a variety of technologies, including metal or ceramic bars that were designed to resonate at the proper frequencies when struck by gravitational waves. By the 1990s, the technology of choice was the laser interferometer, an L-shaped apparatus with two vacuum pipes four feet in diameter through which a laser beam passes. The laser's job is to sense the slightest motion in large glass mirrors hung at the far end of each pipe. Today the LIGO (Laser Interferometry Gravitational-Wave Observatory) project, a cooperative venture between Caltech and the Massachusetts Institute of Technology funded by the National Science Foundation, operates two laser interferometers whose vacuum pipes are four kilometers long: one in Livingston, Louisiana, and the other in Hanford, Washington. The detectors are currently offline while Advanced LIGO, slated to begin operation in 2014, is fitted into the apparatus.

So far the number of gravitational waves we have directly observed is zero.

Professor Adhikari, and indeed the entire LIGO team, is devoted to changing that tally in our favor. Adhikari recently sat down to answer a few questions about his work on LIGO and his experience of the students, staff, and faculty at Caltech.

How did you get started with the search for gravitational waves?

Whoever recruits you into this field says, "This is the best time to get in. You're getting in on the ground floor! The past has been a hard slog, but this is the perfect moment. In the next couple of years, boom! It's all going to play out." I heard that and thought, "Oh yes, I believe you. This is a great deal for me."

Now I say the same thing to potential recruits, but now it's true!

How do you feel about the fact that gravitational waves still haven't been detected?

It can be frustrating. Other astronomers have it a lot easier. Every time they point an instrument at the sky, they detect something. Meanwhile, LIGO has been waiting decades for anything, just one little blip. I went to an astronomy conference in San Francisco a while ago, and I swear, every single person who got up to give a talk said, "For six months we worked on this machine, and then we put it in a remote place in Africa or Chile, and as soon as we did, we saw this pulsar and this explosion. It was wonderful!" When I got up to give my talk, I pounded on the podium for a while and said, "What about me? I've been working on this thing for 15 years, and I've got nothing. Where's my signal?" People came up afterward and patted me on the back and said, "It's all right, it's going to happen for you too, don't worry."

Do you think you will eventually detect gravitational waves?

Yes, if our device is as sensitive as we believe it is, and if the kind of dramatic events that produce significant gravitational waves happen often enough.

I have extremely high confidence that these events are happening. In 1974, two radio astronomers, Russell Hulse and Joe Taylor, then at the University of Massachusetts at Amherst, observed a binary neutron-star system from a radio observatory in Puerto Rico. They and others have been tracking it ever since. The orbit of the stars is gradually decaying, which indicates the presence of gravitation. But more importantly, the decay is exactly as predicted by Einstein's theory. And we know that there are other events like this that would produce gravitational waves. People observe some such events using radio astronomy and optical astronomy. What we don't know is precisely how often they happen.

And you believe that if they happen, LIGO will detect them?

I think the main reason we stick with this effort is because our detectors are working like they should be. We can see a big piece of glass—a 40-kilogram mirror—move back and forth a distance equivalent to one-billionth the size of a hydrogen atom in response to a gravitational wave. You might say it could move by the size of a hydrogen atom and be believed. But one-billionth? Come on. It seems like this level of sensitivity can't be possible. When you tell people how sensitive LIGO is, it sounds like you're a nutcase—but we've measured it to be that precise.

With an instrument that sensitive, how do you avoid measuring everything else?

LIGO reacts to everything. If there's a lightning strike in Kansas, we see a magnetic pulse; if there's an earthquake anywhere in the world, our detector shakes around. Once, we had interference in our signal at the LIGO site in eastern Washington, and it was due to the release of a little extra water by a dam in western Washington.

Our whole concept is to get a thousand different kinds of sensors attached to LIGO: accelerometers, magnetometers, microphones, pressure sensors, devices to measure temperature, cosmic rays, everything. Our detector is the only thing in the world that will ever sense a gravitational wave, because it is so hard to detect. So if you see a blip in any other sensor, you're seeing something other than a gravitational wave.

Are you working to further increase the sensitivity?

All the time. For example, we originally decided to go with glass—fused silica—as the material for the mirrors. People have been studying glass for hundreds of years; it has some almost magical properties that may help LIGO to detect gravitational waves.

More recently we've learned that there may be an even quieter material: silicon crystal. Silicon has some difficult properties, but they vanish at about 120 degrees Kelvin, or about minus 150 degrees centigrade. So now we are looking at developing silicon detectors and keeping them in a cryogenic atmosphere. Unfortunately, this means completely revamping LIGO. So while the next generation of LIGO—Advanced LIGO—is online, we will already be working on its successor.

How are students involved in your work on LIGO?

From the beginning, I thought that if we were going to make LIGO work, we had better get a huge gang of students from Caltech working on this project. That's what makes it all go. My students work from . . . well, sometime after lunch until the sun rises. Starting several years ago, we set students to work on prototyping new, speculative ideas for LIGO. Some of these ideas never add up to anything, but others that we originally thought wouldn't be of any use at all are now the standard vanilla technology of LIGO. We ask ourselves, "How did we ever live without this?"

One of these student projects was to imagine putting a bunch of microphones and vibration sensors around LIGO. Then, without trying to determine which events were creating which reactions, we simply inputted the signals into a computer and told it to subtract the noise out of the interferometer. We found out that there were already learning algorithms like this created by people for other reasons. In fact, to get rid of all kinds of noise in the interferometer we now use similar learning algorithms to those used in noise-canceling headphones.

We have international collaborators in Japan, Italy, France, Germany, Australia, and India, so we always have undergraduate and graduate students coming from these places. Our labs are an international mix of people of different ages and levels. And everyone is really into the project. I don't have to do any cheerleading; they're already self-motivated.

What excites you about Caltech?

Getting to work with the people here. They're all really bright and energetic and thinking about things all the time. Before physics, I had several other jobs, and mostly we tried to figure out how to do the least possible amount of work until five o'clock came around and we could get out. Here the work is so exciting that you can easily lose track of time and leave six hours late.

Caltech is a special place because of its intensity, and also because of all the expertise that is around. We have geophysics, aeronautics, applied physics . . . And the teaching is wonderful. For the past three years I have taught electromagnetism to nonphysics majors. It's full of practical questions like "What is this thing?" I learn a lot from teaching that.

Cynthia Eller
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Tuesday, December 10, 2013
Noyes 153 (J. Holmes Sturdivant Lecture Hall) – Arthur Amos Noyes Laboratory of Chemical Physics

Advice for Future New Faculty: Caltech Postdoc Association Event

Friday, January 10, 2014
Center for Student Services 360 (Workshop Space) – Center for Student Services

Undergraduate Teaching Assistant Orientation

Caltech Names Thomas F. Rosenbaum as New President

To: The Caltech Community

From: Fiona Harrison, Benjamin M. Rosen Professor of Physics and Astronomy, and Chair, Faculty Search Committee; and David Lee, Chair, Board of Trustees, and Chair, Trustee Selection Committee

Today it is our great privilege to announce the appointment of Thomas F. Rosenbaum as the ninth president of the California Institute of Technology.

Dr. Rosenbaum, 58, is currently the John T. Wilson Distinguished Service Professor of Physics at the University of Chicago, where he has served as the university's provost for the past seven years. As a distinguished physicist and expert on condensed matter physics, Dr. Rosenbaum has explored the quantum mechanical nature of materials, making major contributions to the understanding of matter near absolute zero, where such quantum mechanical effects dominate. His experiments in quantum phase transitions in matter are recognized as having played a key role in placing these transitions on a theoretical level equivalent to that which has been developed for classical systems.

But Dr. Rosenbaum's scientific achievements were not solely what captured and held the attention of those involved in the presidential search. We on the search committee were impressed by Dr. Rosenbaum's deep dedication, as Chicago's provost, to both undergraduate and graduate education—both critical parts of Caltech's mission. He has had responsibility for an unusually broad range of institutions and intellectual endeavors. Among his achievements as provost was the establishment of the Institute for Molecular Engineering in 2011, the University of Chicago's very first engineering program, in collaboration with Argonne National Lab.

We also believe that Dr. Rosenbaum's focus on strengthening the intellectual ties between the University of Chicago and Argonne National Lab will serve him well in furthering the Caltech-JPL relationship.

As provost, Dr. Rosenbaum was also instrumental in establishing collaborative educational programs serving communities around Chicago's Hyde Park campus, including the university's founding of a four-campus charter school that was originally designed to further fundamental research in education but which has also achieved extraordinary college placement results for disadvantaged Chicago youths.

This successful conclusion to our eight-month presidential search was result of the hard work of the nine-member Faculty Search Committee, chaired by Fiona Harrison, and the 10-member Trustee Selection Committee, chaired by David Lee. We are grateful both to the trustees and faculty on our two committees who made our job so very easy as well as to those faculty, students, staff, and alumni who provided us with input and wisdom as we scoured the country for just the right person for our Caltech.

"Tom embodies all the qualities the faculty committee hoped to find in our next president," Harrison says. "He is a first-rate scholar and someone who understands at a deep level the commitment to fundamental inquiry that characterizes Caltech. He is also the kind of ambitious leader who will develop the faculty's ideas into the sorts of innovative ventures that will maintain Caltech's position of prominence in the next generation of science and technology."

"The combination of deep management experience and visionary leadership Tom brings will serve Caltech extremely well in the coming years," Lee adds. "The Board is excited about collaborating closely with Tom to propel the Institute to new levels of scientific leadership."

"The Caltech community's palpable and deep commitment to the Institute came through in all my conversations, and it forms the basis for Caltech's and JPL's lasting impact," Dr. Rosenbaum says. "It will be a privilege to work closely with faculty, students, staff, and trustees to explore new opportunities, building on Caltech's storied accomplishments."

Dr. Rosenbaum received his bachelor's degree in physics with honors from Harvard University in 1977, and both an MA and PhD in physics from Princeton University in 1979 and 1982, respectively. He did research at Bell Laboratories and at IBM Watson Research Center before joining the University of Chicago's faculty in 1983. Dr. Rosenbaum directed the university's Materials Research Laboratory from 1991 to 1994 and its interdisciplinary James Franck Institute from 1995 to 2001 before serving as vice president for research and for Argonne National Laboratory from 2002 to 2006. He was named the university's provost in 2007. His honors include an Alfred P. Sloan Research Fellowship, a Presidential Young Investigator Award, and the William McMillan Award for "outstanding contributions to condensed matter physics." Dr. Rosenbaum is an elected fellow of the American Physical Society, the American Association for the Advancement of Science, and the American Academy of Arts and Sciences.

Joining the Caltech faculty will be Dr. Rosenbaum's spouse, Katherine T. Faber, the Walter P. Murphy Professor of Materials Science and Engineering at Northwestern University. Dr. Faber's research focuses on understanding stress fractures in ceramics, as well as on the fabrication of ceramic materials with controlled porosity, which are important as thermal and environmental barrier coatings for engine components. Dr. Faber is also the codirector of the Northwestern University-Art Institute of Chicago Center for Scientific Studies in the Arts (NU-ACCESS), which employs advanced materials science techniques for art history and restoration. Dr. Rosenbaum and Dr. Faber have two sons, Daniel, who graduated from the University of Chicago in 2012, and Michael, who is currently a junior there.

Dr. Rosenbaum will succeed Jean-Lou Chameau, who served the Institute from 2006 to 2013, and will take over the helm from interim president and provost Ed Stolper on July 1, 2014. The board, the search committee, and, indeed, the entire Institute owes Dr. Stolper a debt of gratitude for his unwavering commitment to Caltech, and for seamlessly continuing the Institute's forward momentum through his interim presidency.

As you meet Dr. Rosenbaum today and over the coming months, and learn more about his vision for Caltech's future, we believe that you will quickly come to see why he is so well suited to guide Caltech as we continue to pursue bold investigations in science and engineering, to ready the next generation of scientific and thought leaders, and to benefit humankind through research that is integrated with education.

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Caltech Nobelist Zewail Named to UN Scientific Advisory Board

Ahmed Zewail, Linus Pauling Professor of Chemistry and professor of physics, has been selected as one of 26 members of a new Scientific Advisory Board established by the United Nations secretary-general.

The board, which will meet twice per year, will provide advice on science, technology, and innovation concerning sustainable development to the secretary-general and the heads of UN organizations. The creation of this new board, which was formally announced September 24 at the UN's first High-Level Political Forum on Sustainable Development, was the result of a recommendation from the report of the High-Level Panel on Global Sustainability in January 2012.

Made up of scientists from various fields in the natural, social, and human sciences, the board will have the main objective of improving the linkage between science and policy and of ensuring that up-to-date and rigorous science is reflected in policy discussions within the UN. In addition, board members will also advise on issues related to the public visibility and public understanding of science. The United Nations Educational Scientific and Cultural Organization (UNESCO) will serve as the secretariat of the board.

"I am pleased to be a member of this United Nations Scientific Advisory Board. Its objectives coincide with my vision to promote science in education and science in diplomacy," Zewail says. "The UN is an excellent platform for an outreach to all nations."

In 1999, Professor Zewail was awarded the Nobel Prize in Chemistry for developing the field of femtochemistry, which uses ultrashort laser flashes to enable the study of chemical reactions in real time at the scale of quadrillionths of a second. He and his group later developed a technique called four-dimensional electron microscopy for the direct imaging of matter in the three dimensions of space and in time with applications spanning the physical and biological sciences.

He is currently director of the Center for Physical Biology at Caltech funded by the Moore Foundation.

Zewail's new involvement with the UN reflects his long-standing interest in global affairs, particularly as they relate to science, education, and world peace. His commentaries on such global issues have been presented in numerous articles, a number of books, and public addresses all over the world. Since the 2011 revolution in Egypt—his native country—Zewail has also played a critical role in that nation's events.

In addition to his international interests, Zewail has been involved in domestic science policy. In 2009, he was appointed to President Obama's Council of Advisors on Science and Technology, and he was named the first U.S. Science Envoy to the Middle East as part of a program sponsored by the White House and the State Department to foster science and technology collaborations between the United States and nations throughout the Middle East, North Africa, and South and Southeast Asia.

Among other honors, Zewail has received the Albert Einstein World Award of Science, the Benjamin Franklin Medal, the Robert A. Welch Award, the Leonardo da Vinci Award, the Wolf Prize, the Priestley Medal, and the King Faisal International Prize. He is a recipient of the Grand Collar of the Order of the Nile, Egypt's highest state honor, and has been featured on postage stamps issued to honor his contributions to science and humanity. Zewail holds honorary degrees from 40 universities around the world and is an elected member of many professional academies and societies, including the National Academy of Sciences, the American Philosophical Society, The Royal Society of London, and the Swedish, Russian, Chinese, and French academies. In recognition of his contributions as a world leader in science and public service, he has received the Top American Leaders award given jointly by the Washington Post and Harvard Kennedy School's Center for Public Leadership.

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Reducing Coincidence with Mathematics: An Interview with Nets Katz

Raised in Grand Prairie, Texas, Nets Katz began pursuing mathematics at an early age, earning a bachelor's from Rice University in 1990 at the age of 17 and a doctorate from the University of Pennsylvania in 1993 at 20. After completing several postdoctoral fellowships, Katz went on to an assistant professorship at the University of Illinois at Chicago, an associate professorship at Washington University in Saint Louis, and a full professorship at Indiana University before joining the faculty at Caltech in January. Recently, Katz answered a few questions about his move to Southern California and his research in a field of math called combinatorics.

What brought you to Caltech, and why are you excited to be here?

I was offered a job here! It's a great institution; I've always admired it. Tom Wolff, who was a math professor here about 12 years ago, was a major influence in my career, and I flatter myself to think that I'm continuing some of his work.

I'm also really excited about teaching these students. I'm teaching Math 1 in the fall, and I'm really looking forward to the unique opportunity to get across deep and useful ideas to the very best students, including students who aren't in my field. Mathematics has always had a significant impact on the other sciences and engineering, and I think it will continue to do so.

What are your research interests?

I'm interested in showing that you can't have very many coincidences. The problems that I'm interested in are mostly considered to be in combinatorics [a field of math concerned with finding maximum, minimum, and optimum configurations—such as the absolute largest or smallest possible size of an object]. In a problem I worked on a few years ago, called the Erdos distance problem, we wanted to know the minimum number of distinct distances possible between a set number of points in a plane.

For example, say you're playing a game in which you ask an opponent to draw a finite number of n dots on a sheet of paper; the object of the game is for the opponent to position their dots so that the number of distinct distances between the dots is as small as possible. You then determine how well they did by tallying the number of distinct distances between these dots. If the dots are truly positioned randomly, some of the distances between the dots could be the same, but almost all of the distances will be different—meaning your opponent didn't do very well.

Placing the dots in a grid-like lattice pattern would be a relatively good strategy to win the game—this arrangement allows you to position the dots in such a way that a lot of the distances are the same. When working on this problem, we were able to prove that you can't get fewer than n/log n distinct distances—which, surprisingly, means that there isn't a strategy much better than the lattice. If there were a better strategy or design, it would involve a lot of coincidences—and too many coincidences aren't possible. You have to have some really incredibly special design to come close to the lattice arrangement, and what we were able to show is that even the best "incredibly special design" really isn't better than the lattice by very much.

How did you first become interested in math?

My father was a physicist, so we would have conversations about math at the dinner table. Of course, he was very far from a mathematician, but among physicists in his day he was quite well versed in math. And he had criticisms of how math was done, not all of which made sense, so we would have discussions about the foundations of things that were really exciting.

Here we were in Grand Prairie—I, a little kid no one had ever heard of, and he, a physicist largely forgotten—talking about how we might set the foundations of mathematics in a more clever way than all the denizens of the MITs and Caltechs of the world had ever managed to do. It was incredibly empowering. If it weren't constrained by the substantive requirements of mathematics, it might have been megalomaniacal. He made me feel that a person out of nowhere could really change the way people think about things. This was very exciting to me.

How do you like living in Southern California?

Actually, I have to admit I'm much more of an Indiana person—I prefer small towns and rural areas to densely populated cities—so I find I am experiencing a lot of culture shock living in Southern California. But there are nice things about the location; I have a lot of friends at UCLA and being closer is definitely a plus.

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Sky Survey Captures Key Details of Cosmic Explosions

Caltech astronomers report on unique results from the intermediate Palomar Transient Factory

Developed to help scientists learn more about the complex nature of celestial objects in the universe, astronomical surveys have been cataloguing the night sky since the beginning of the 20th century. The intermediate Palomar Transient Factory (iPTF)—led by the California Institute of Technology (Caltech)—started searching the skies for certain types of stars and related phenomena in February. Since its inception, iPTF has been extremely successful in the early discovery and rapid follow-up studies of transients—astronomical objects whose brightness changes over timescales ranging from hours to days—and two recent papers by iPTF astronomers describe first-time detections: one, the progenitor of a rare type of supernova in a nearby galaxy; the other, the afterglow of a gamma-ray burst in July.

The iPTF builds on the legacy of the Caltech-led Palomar Transient Factory (PTF), designed in 2008 to systematically chart the transient sky by using a robotic observing system mounted on the 48-inch Samuel Oschin Telescope on Palomar Mountain near San Diego, California. This state-of-the-art, robotic telescope scans the sky rapidly over a thousand square degrees each night to search for transients.

Supernovae—massive exploding stars at the end of their life span—make up one important type of transient. Since PTF's commissioning four years ago, its scorecard stands at over 2,000 spectroscopically classified supernovae. The unique feature of iPTF is brand-new technology that is geared toward fully automated, rapid response and follow-up within hours of discovery of a new supernova.

The first paper, "Discovery, Progenitor and Early Evolution of a Stripped Envelope Supernova iPTF13bvn," appears in the September 20 issue of Astrophysical Journal Letters and describes the detection of a so-called Type Ib supernova. Type Ib supernovae are rare explosions where the progenitor star lacks an outer layer of hydrogen, the most abundant element in the universe, hence the "stripped envelope" moniker. It has proven difficult to pin down which kinds of stars give rise to Type Ib supernovae. One of the most promising ideas, says graduate student and lead author Yi Cao, is that they originate from Wolf-Rayet stars. These objects are 10 times more massive and thousands of times brighter than the sun and have lost their hydrogen envelope by means of very strong stellar winds. Until recently, no solid evidence existed to support this theory. Cao and colleagues believe that a young supernova that they discovered, iPTF13bvn, occurred at a location formerly occupied by a likely Wolf-Rayet star.

Supernova iPTF13bvn was spotted on June 16, less than a day after the onset of its explosion. With the aid of the adaptive optics system used by the 10-meter Keck telescopes in Hawaii—which reduces the blurring effects of Earth's atmosphere—the team obtained a high-resolution image of this supernova to determine its precise position. Then they compared the Keck image to a series of pictures of the same galaxy (NGC 5806) taken by the Hubble Space Telescope in 2005, and found one starlike source spatially coincident to the supernova. Its intrinsic brightness, color, and size—as well as its mass-loss history, inferred from supernova radio emissions—were characteristic of a Wolf-Rayet star.

"All evidence is consistent with the theoretical expectation that the progenitor of this Type Ib supernova is a Wolf-Rayet star," says Cao. "Our next step is to check for the disappearance of this progenitor star after the supernova fades away. We expect that it will have been destroyed in the supernova explosion."

Though Wolf-Rayet progenitors have long been predicted for Type Ib supernova, the new work represents the first time researchers have been able to fill the gap between theory and observation, according to study coauthor and Caltech alumna Mansi Kasliwal (PhD '11). "This is a big step in our understanding of the evolution of massive stars and their relation to supernovae," she says.

The second paper, "Discovery and Redshift of an Optical Afterglow in 71 degrees squared: iPTF13bxl and GRB 130702A," appears in the October 20 issue of Astrophysical Journal Letters. Lead author Leo Singer, a Caltech grad student, describes finding and characterizing the afterglow of a long gamma-ray burst (GRB) as being similar to digging a needle out of a haystack.

Long GRBs, which are the brightest known electromagnetic events in the universe, are also connected with the deaths of rapidly spinning, massive stars. Although such GRBs initially are detected by their high-energy radiation—GRB 130702A, for example, was first located by NASA's Fermi Gamma-ray Space Telescope—an X-ray or visible-light afterglow must also be found to narrow down a GRB's position enough so that its location can be pinpointed to one particular galaxy and to determine if it is associated with a supernova.

After Fermi's initial detection of GRB 130702A, iPTF was able to narrow down the GRB's location by scanning an area of the sky over 360 times larger than the face of the moon and sifting through hundreds of images using sophisticated machine-learning software; it also revealed the visible-light counterpart of the burst, designated iPTF13bxl. This is the first time that a GRB's position has been determined precisely using optical telescopes alone.

After making the initial correlation between the GRB and the afterglow, Singer and colleagues corroborated their results and gained additional information using a host of other instruments, including optical, X-ray, and radio telescopes. In addition, ground-based telescopes around the world monitored the afterglow for days as it faded away, and recorded the emergence of a supernova five days later.

According to Singer, GRB130702A / iPTF13bxl turned out to be special in many ways.

"First, by measuring its redshift, we learned that it was pretty nearby as far as GRBs go," he says. "It was pretty wimpy compared to most GRBs, liberating only about a thousandth as much energy as the most energetic ones. But we did see it eventually turn into a supernova. Typically we only detect supernovae in connection with nearby, subluminous GRBs, so we can't be certain that cosmologically distant GRBs are caused by the same kinds of explosions."

"The first results from iPTF bode well for the discovery of many more supernovae in their infancy and many more afterglows from the Fermi satellite", says Shrinivas Kulkarni, the John D. and Catherine T. MacArthur Professor of Astronomy and Planetary Science at Caltech and principal investigator for both the PTF and iPTF.

The iPTF project is a scientific collaboration between Caltech; Los Alamos National Laboratory; the University of Wisconsin, Milwaukee; the Oskar Klein Centre in Sweden; the Weizmann Institute of Science in Israel; the TANGO Program of the University System of Taiwan; and the Kavli Institute for the Physics and Mathematics of the Universe in Japan.


Katie Neith
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Let There Be Light: Finding the Earliest Galaxies

Watson Lecture Preview

Richard S. Ellis, the Steele Family Professor of Astronomy, is on the verge of seeing as far back as it is possible to see—not quite back to the dawn of time itself but to the dawn of the first galaxies. He describes the journey at 8 p.m. on Wednesday, October 16, in Caltech's Beckman Auditorium. Admission is free.


Q: What do you do?

A: I study distant galaxies. When we look deep into space with the Hubble Space Telescope and at the W. M. Keck Observatory, we're looking back in time. I'm trying to look back to the moment the very first stars switched on—to the "cosmic dawn." Before then, there was no starlight, and we call that period the Dark Ages.

The universe today is 13.8 billion years old, and we can now look about 97 percent of the way back to the Big Bang. We think we need to look maybe another half-percent farther back, or about another 100 million years, in order to find the very earliest objects. We will do this with a large telescope called the Thirty Meter Telescope, which should begin construction in April, and the James Webb Space Telescope, which, I hope, will be launched in 2018.

The very first stars would only contain hydrogen and helium, and we will be able to recognize them by their colors and spectra. Our models tell us that such objects, free from heavy elements such as magnesium and iron, should be extraordinarily blue.

You might ask, "Why is this important?" And the answer is that, in many ways, we're searching for our origins. Stars produced the elements that make up you and me and everything else around us. We are, in a sense, stardust. The discovery of the microwave background radiation from the Big Bang was a big milestone in cosmic history. The moment when the universe switched on its starlight—cosmic dawn—is another important milestone.


Q: What is the best thing about what you do?

A: Above all, I like observing with large telescopes; it's inspirational to search for objects that are extraordinarily distant. And I like working with graduate students; it's remarkable that Caltech students can accompany me to the telescope and share in the discoveries.


Q: How did you get into this line of work?

A: I became convinced I wanted to be an astronomer when I was six years old. I grew up in Wales, and our public library had a little book called Out Into Space by the late Sir Patrick Moore, the famous popularizer of astronomy. It was about a boy and girl who went to their eccentric uncle's house, and he had a telescope. That hooked me. I never wanted to do anything else. Forty years later, I appeared on his television program, The Sky at Night, and he gave me a signed copy. And when I reread it, I still remembered the relevant chapters.


Q: So, do you now qualify as an eccentric uncle yourself?

A: I do, yeah [laughter]. I am an uncle, and I definitely am eccentric. You can ask my sister's kids [more laughter].


Named for the late Caltech professor Earnest C. Watson, who founded the series in 1922, the Watson Lectures present Caltech and JPL researchers describing their work to the public. Many past Watson Lectures are available online at Caltech's iTunes U site.

Douglas Smith
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Watson Lecture: Let There Be Light: Finding the Earliest Galaxies
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