After a Half Century, the Exotic Pentaquark Particle is Found

In July, scientists at the Large Hadron Collider (LHC) reported the discovery of the pentaquark, a long-sought particle first predicted to exist in the 1960s as a consequence of the theory of elementary particles and their interactions proposed by Murray Gell-Mann, Caltech's Robert Andrews Millikan Professor of Theoretical Physics, Emeritus.

In work for which he won the Nobel Prize in Physics in 1969, Gell-Mann introduced the concept of the quark—a fundamental building block of matter. Quarks come in six types, known as "flavors": up, down, top, bottom, strange, and charm. As described in his model, groups of quarks combine into composite particles called hadrons. Combining a quark and an antiquark (a quark's antimatter equivalent) creates a type of hadron called a meson, while baryons are hadrons composed of three quarks. Protons, for example, have two up quarks and one down quark, while neutrons have one up and two down quarks. Gell-Mann's scheme also allowed for more exotic forms of composite particles, including tetraquarks, made of four quarks, and the pentaquark, consisting of four quarks and an antiquark.

The pentaquark was detected at the LHC—the most powerful particle accelerator on Earth—by scientists carrying out the "beauty" experiment, or LHCb. The LHC accelerates protons around a ring almost five miles wide to nearly the speed of light, producing two proton beams that careen toward each other. A small fraction of the protons collide, creating other particles in the process. During investigations of the behavior of one such particle, an unstable three-quark object known as the bottom lambda baryon that decays quickly once formed, LHCb researchers observed unusually heavy objects, each with about 4.5 times the mass of a proton. After further analysis, the researchers concluded that the objects were pentaquarks composed of two up quarks, one down quark, one charm quark, and one anticharm quark. A paper describing the discovery has been published in the journal Physical Review Letters.

It is thought that pentaquarks and other exotic particles may form naturally in violent environments such as exploding stars and would have been created during the Big Bang. A better understanding of these complex arrangements of quarks could offer insight into the forces that hold together all matter as well as the earliest moments of the universe.

"This is part of a long process of discovery of particle states," said Gell-Mann in a statement released by the Santa Fe Institute, where he currently is a Distinguished Fellow. "[In the future] they may find more and more of them, made of quarks and antiquarks and various combinations."

Contact: 
Writer: 
Exclude from News Hub: 
No
News Type: 
Research News

Physicist Charles A. Barnes Dies

1921–2015

Charles A. Barnes, professor of physics, emeritus, at Caltech and an expert in the study of both the weak nuclear force—one of the fundamental forces of nature—and of the nuclear reactions that produce the majority of the elements in our universe, passed away on Friday, August 14, 2015. He was 93.

"Caltech was the place at which nuclear astrophysics was invented, and Charlie made many fundamental contributions in this field," says Fiona Harrison, the Kent and Joyce Kresa Leadership Chair of Caltech's Division of Physics, Mathematics and Astronomy and Benjamin Rosen Professor of Physics.

Born on December 12, 1921, in Toronto, Canada, Barnes received his bachelor of arts degree in physics and mathematics from McMaster University in 1943 and his master of arts degree in physics from the University of Toronto in 1944. He earned a doctorate in physics from the University of Cambridge in 1950. He came to Caltech as a research fellow in 1953 and became a senior research fellow in 1954, an associate professor in 1958, and a professor in 1962. Barnes retired in 1992.

Barnes was a fellow of the American Physical Society and the American Association for the Advancement of Science.

An experimental physicist who specialized in nuclear physics, Barnes performed pioneering research in two key areas. The first was in the study of the so-called nuclear weak force, which governs the radioactive decay of elements and is responsible for the fusion of protons to form deuterium. This fusion releases the energy that is the source of heat from our sun and other stars.

During the 1960s and 70s, in experiments using the particle accelerators in the basements of Caltech's Kellogg Radiation Laboratory and Alfred P. Sloan Laboratory of Mathematics and Physics, Barnes studied the breakdown of "mirror symmetry" in the weak force, the phenomenon that causes an experiment and its mirror experiment to give different results. "This is a surprising and novel feature of the weak nuclear force," says Caltech professor of physics Bradley W. Filippone.

Barnes was also an expert in nucleosynthesis, the formation of new atomic nuclei from simpler ones, a process that occurs on a cosmic scale in the cores of stars.  

"He is probably best known for his nucleosynthesis studies of the nuclear reaction that produces oxygen from carbon and helium," says Filippone. In 1974, Barnes and his student Peggy Dyer (PhD '73) performed the first careful measurement of this reaction. Over the next two decades, in collaboration with Filippone and others, Barnes improved upon the measurement; their work culminated in a precision measurement at TRIUMF, Canada's national laboratory for particle and nuclear physics, in 1993. This reaction rate was called "a problem of paramount importance" by Caltech's William A. Fowler, co-winner of the 1983 Nobel Prize in Physics for his research into the creation of chemical elements inside stars, in his Nobel address. Through his work, Barnes provided critical input in determining the final distribution of the chemical elements produced in stars—and whether the final fate of a star is to become a black hole or some other celestial object, such as a neutron star.

In addition to his scientific achievements, Barnes will be remembered fondly for his support of young scientists. "He was a superb mentor to young scientists—including me—providing encouragement, enthusiasm, and great ideas to a generation of nuclear physicists studying both the weak nuclear force as well as nuclear reactions that occur in stars," says Filippone.

"Charlie was still active when I came to Caltech, and I remember conversations with him about signatures we could look for to identify how rare chemical elements are manufactured in the universe," Harrison says.

"Charlie was a wonderful person, scientist, and collaborator," says George L. Argyros Professor of Chemistry Nate Lewis (BS '77, MS '77), who worked with Barnes during the late 1980s. "He was thorough, scholarly, and curious, and a shining example of the best qualities in a long tradition of truly world-class experimental nuclear physicists at Caltech."

Barnes was predeceased by his wife of six decades, Phyllis, who passed away on August 12, 2013. He is survived by his son, Steven Barnes, and his daughter, Nancy Wetherow; by four grandchildren; and by two great-grandchildren.

Writer: 
Kathy Svitil
Writer: 
Exclude from News Hub: 
No
News Type: 
In Our Community

Caltech Theoretical Physicist Receives the 2015 Dirac Medal and Prize

Alexei Kitaev, the Ronald and Maxine Linde Professor of Theoretical Physics and Mathematics, has been awarded the 2015 Dirac Medal and Prize from the Abdus Salam International Centre for Theoretical Physics (ICTP). The prize, named after the esteemed theoretical physicist and Nobel Laureate Paul Dirac, is one of the most prestigious honors in theoretical physics. This year it was awarded jointly to Kitaev, Gregory W. Moore of Rutgers University, and Nicholas Read of Yale University for their work on condensed matter research.

The work of Kitaev, Moore, and Read has "played a fundamental role in recent advances in our understanding of the quantum states of matter and quantum entanglement theory," according to the ICTP's press release.

Kitaev is cited for proposing an innovative method of computation, called topological quantum computation, which builds upon Moore and Read's theory of non-Abelian anyons. Anyons are special quasiparticles that exist under the conditions of the fractional quantum Hall effect (FQHE). The FQHE is observed in semiconductor structures that contain a thin layer of mobile electrons. When such systems are cooled to very low temperatures and immersed in a strong magnetic field, the electrons form a collective state analogous to a liquid.

"Anyons are like bubbles and lumps in that liquid, which can move around, fuse, or annihilate," Kitaev explains. "However, these quasiparticles have very strange properties: they carry a fractional electron charge and defy the textbook classification into bosons and fermions. For bosons, such as photons, switching the places of two identical particles has no effect, while for fermions like electrons or protons, the particle exchange introduces a minus sign into the calculation. Switching the places of two identical anyons results in an extra factor other that 1 or -1."

"Non-Abelian anyons are even weirder because their state is not determined by where they are spatially; there is also some hidden state in the liquid between them. Exchanging two particles or moving one around the other alters that state."

As part of his proposed method of topological quantum computation, Kitaev suggested that using this hidden state as a quantum computer memory could make such computation more stable and error proof.

"Kitaev's work on fault-tolerant quantum computation using topological quantum phases with non-Abelian quasiparticles has had profound implications in quantum information theory," the award citation notes.

Caltech faculty who have previously been awarded the Dirac Medal are John H. Schwarz, the Harold Brown Professor of Theoretical Physics, Emeritus, in 1989; and John Hopfield, the Roscoe G. Dickinson Professor of Chemistry and Biology, Emeritus, in 2001.

Writer: 
Exclude from News Hub: 
No
News Type: 
In Our Community

High School Students Visit for Women in STEM Preview Day

On Friday, August 7, 104 female high school seniors and their families visited Caltech for the fourth annual Women in STEM (WiSTEM) Preview Day, hosted by the undergraduate admissions office. The event was designed to explore the accomplishments and continued contributions of Caltech women in the disciplines of science, technology, engineering, and mathematics (STEM).

The day opened with a keynote address by Marianne Bronner, the Albert Billings Ruddock Professor of Biology and executive officer for neurobiology. Bronner, who studies the development of the central nervous system, spoke about her experiences in science and at Caltech.

"Caltech is an exciting place to be. It's a place where you can be creative and think outside the box," she said. "My advice to you would be to try different things, play around, and do what makes you happy." Bronner ended her address by noting the pleasure she takes in mentoring young scientists, and especially young women. "I was just like you," she said.

Over the course of the day, students and their families attended panels on undergraduate research opportunities and participated in social events where current students shared their experiences of Caltech life. They also listened to presentations from female scientists and engineers of the Jet Propulsion Laboratory.

"I really love science, and it's so exciting to be around all of these other people who share that," says Sydney Feldman, a senior from Maryland. "I switched around my whole summer visit schedule to come to this event and I'm having such a great time."

The annual event began four years ago with the goal of encouraging interest in STEM in high school women and ultimately increasing applications to Caltech by female candidates. In 2009, a U.S. Department of Commerce study showed that women make up 24 percent of the STEM workforce and hold a disproportionately low share of undergraduate degrees in STEM fields.

"Women are seriously underrepresented in these fields," says Caltech admissions counselor and WiSTEM coordinator Abeni Tinubu. "Our event really puts emphasis on how Caltech supports women on campus, and we want to show prospective students that."

This year, the incoming freshman class is a record 47 percent female students. "This is hugely exciting," says Jarrid Whitney, the executive director of admissions and financial aid. "We've been working hard toward our goal of 50 percent women, and it is clearly paying off thanks to the support of President Rosenbaum and the overall Caltech community."

Frontpage Title: 
Women in STEM Preview Day
Listing Title: 
Women in STEM Preview Day
Writer: 
Exclude from News Hub: 
No
News Type: 
In Our Community

Caltech Announces Discovery in Fundamental Physics

When the transistor was invented in 1947 at Bell Labs, few could have foreseen the future impact of the device. This fundamental development in science and engineering was critical to the invention of handheld radios, led to modern computing, and enabled technologies such as the smartphone. This is one of the values of basic research.

In a similar fashion, a branch of fundamental physics research, the study of so-called correlated electrons, focuses on interactions between the electrons in metals.

The key to understanding these interactions and the unique properties they produce—information that could lead to the development of novel materials and technologies—is to experimentally verify their presence and physically probe the interactions at microscopic scales. To this end, Caltech's Thomas F. Rosenbaum and colleagues at the University of Chicago and the Argonne National Laboratory recently used a synchrotron X-ray source to investigate the existence of instabilities in the arrangement of the electrons in metals as a function of both temperature and pressure, and to pinpoint, for the first time, how those instabilities arise. Rosenbaum, professor of physics and holder of the Sonja and William Davidow Presidential Chair, is the corresponding author on the paper that was published on July 27, 2015, in the journal Nature Physics.

"We spent over 10 years developing the instrumentation to perform these studies," says Yejun Feng of Argonne National Laboratory, a coauthor of the paper. "We now have a very unique capability that's due to the long-term relationship between Dr. Rosenbaum and the facilities at the Argonne National Laboratory."

Within atoms, electrons are organized into orbital shells and subshells. Although they are often depicted as physical entities, orbitals actually represent probability distributions—regions of space where electrons have a certain likelihood of being found in a particular element at a particular energy. The characteristic electron configuration of a given element explains that element's peculiar properties.

The work in correlated electrons looks at a subset of electrons. Metals, as an example, have an unfilled outermost orbital and electrons are free to move from atom to atom. Thus, metals are good electrical conductors. When metal atoms are tightly packed into lattices (or crystals) these electrons mingle together into a "sea" of electrons. The metallic element mercury is liquid at room temperature, in part due to its electron configuration, and shows very little resistance to electric current due to its electron configuration. At 4 degrees above absolute zero (just barely above -460 degrees Fahrenheit), mercury's electron arrangement and other properties create communal electrons that show no resistance to electric current, a state known as superconductivity.

Mercury's superconductivity and similar phenomena are due to the existence of many pairs of correlated electrons. In superconducting states, correlated electrons pair to form an elastic, collective state through an excitation in the crystal lattice known as a phonon (specifically, a periodic, collective excitation of the atoms). The electrons are then able to move cooperatively in the elastic state through a material without energy loss.

Electrons in crystals can interact in many ways with the periodic structure of the underlying atoms. Sometimes the electrons modulate themselves periodically in space. The question then arises as to whether this "charge order" derives from the interactions of the electrons with the atoms, a theory first proposed more than 60 years ago, or solely from interactions among the sea of electrons themselves. This question was the focus of the Nature Physics study. Electrons also behave as microscopic magnets and can demonstrate "spin order," which raises similar questions about the origin of the local magnetism.

To see where the charge order arises, the researchers turned to the Advanced Photon Source at Argonne. The Photon Source is a synchrotron (a relative of the cyclotron, commonly known as an "atom-smasher"). These machines generate intense X-ray beams that can be used for X-ray diffraction studies. In X-ray diffraction, the patterns of scattered X-rays are used to provide information about repeating structures with wavelengths at the atomic scale.

In the experiment, the researchers used the X-ray beams to investigate charge-order effects in two metals, chromium and niobium diselenide, at pressures ranging from 0 (a vacuum) to 100 kilobar (100,000 times normal atmospheric pressure) and at temperatures ranging from 3 to 300 K (or -454 to 80 degrees Fahrenheit). Niobium diselenide was selected because it has a high degree of charge order, while chromium, in contrast, has a high degree of spin order. 

The researchers found that there is a simple correlation between pressure and how the communal electrons organize themselves within the crystal. Materials with completely different types of crystal structures all behave similarly. "These sorts of charge- and spin-order phenomena have been known for a long time, but their underlying mechanisms have not been understood until now," says Rosenbaum.

Paper coauthors Jasper van Wezel, formerly of Argonne National Laboratory and presently of the Institute for Theoretical Physics at the University of Amsterdam, and Peter Littlewood, a professor at the University of Chicago and the director of Argonne National Laboratory, helped to provide a new theoretical perspective to explain the experimental results.

Rosenbaum and colleagues point out that there are no immediate practical applications of the results. However, Rosenbaum notes, "This work should have applicability to new materials as well as to the kind of interactions that are useful to create magnetic states that are often the antecedents of superconductors," says Rosenbaum.

"The attraction of this sort of research is to ask fundamental questions that are ubiquitous in nature," says Rosenbaum. "I think it is very much a Caltech tradition to try to develop new tools that can interrogate materials in ways that illuminate the fundamental aspects of the problem." He adds, "There is real power in being able to have general microscopic insights to develop the most powerful breakthroughs."

The coauthors on the paper, titled "Itinerant density wave instabilities at classical and quantum critical points," are Yejun Feng and Peter Littlewood of the Argonne National Laboratory, Jasper van Wezel of the University of Amsterdam, Daniel M. Silevitch and Jiyang Wang of the University of Chicago, and Felix Flicker of the University of Bristol. Work performed at the Argonne National Laboratory was supported by the U.S. Department of Energy. Work performed at the University of Chicago was funded by the National Science Foundation. Additional support was received from the Netherlands Organization for Scientific Research.

Contact: 
Writer: 
Exclude from News Hub: 
No
News Type: 
Research News

Caltech Astronomers Unveil a Distant Protogalaxy Connected to the Cosmic Web

A team of astronomers led by Caltech has discovered a giant swirling disk of gas 10 billion light-years away—a galaxy-in-the-making that is actively being fed cool primordial gas tracing back to the Big Bang. Using the Caltech-designed and -built Cosmic Web Imager (CWI) at Palomar Observatory, the researchers were able to image the protogalaxy and found that it is connected to a filament of the intergalactic medium, the cosmic web made of diffuse gas that crisscrosses between galaxies and extends throughout the universe.

The finding provides the strongest observational support yet for what is known as the cold-flow model of galaxy formation. That model holds that in the early universe, relatively cool gas funneled down from the cosmic web directly into galaxies, fueling rapid star formation.

A paper describing the finding and how CWI made it possible currently appears online and will be published in the August 13 print issue of the journal Nature.

"This is the first smoking-gun evidence for how galaxies form," says Christopher Martin, professor of physics at Caltech, principal investigator on CWI, and lead author of the new paper. "Even as simulations and theoretical work have increasingly stressed the importance of cold flows, observational evidence of their role in galaxy formation has been lacking."


Caltech Astronomers Discuss Findings on Galaxy Formation

The protogalactic disk the team has identified is about 400,000 light-years across—about four times larger in diameter than our Milky Way. It is situated in a system dominated by two quasars, the closest of which, UM287, is positioned so that its emission is beamed like a flashlight, helping to illuminate the cosmic web filament feeding gas into the spiraling protogalaxy.

Last year, Sebastiano Cantalupo, then of UC Santa Cruz (now of ETH Zurich) and his colleagues published a paper, also in Nature, announcing the discovery of what they thought was a large filament next to UM287. The feature they observed was brighter than it should have been if indeed it was only a filament. It seemed that there must be something else there.

In September 2014, Martin and his colleagues, including Cantalupo, decided to follow up with observations of the system with CWI. As an integral field spectrograph, CWI allowed the team to collect images around UM287 at hundreds of different wavelengths simultaneously, revealing details of the system's composition, mass distribution, and velocity.

Martin and his colleagues focused on a range of wavelengths around an emission line in the ultraviolet known as the Lyman-alpha line. That line, a fingerprint of atomic hydrogen gas, is commonly used by astronomers as a tracer of primordial matter.

The researchers collected a series of spectral images that combined to form a multiwavelength map of a patch of sky around the two quasars. This data delineated areas where gas is emitting in the Lyman-alpha line, and indicated the velocities with which this gas is moving with respect to the center of the system.

"The images plainly show that there is a rotating disk—you can see that one side is moving closer to us and the other is moving away. And you can also see that there's a filament that extends beyond the disk," Martin says. Their measurements indicate that the disk is rotating at a rate of about 400 kilometers per second, somewhat faster than the Milky Way's own rate of rotation.

"The filament has a more or less constant velocity. It is basically funneling gas into the disk at a fixed rate," says Matt Matuszewski (PhD '12), an instrument scientist in Martin's group and coauthor on the paper. "Once the gas merges with the disk inside the dark-matter halo, it is pulled around by the rotating gas and dark matter in the halo." Dark matter is a form of matter that we cannot see that is believed to make up about 27 percent of the universe. Galaxies are thought to form within extended halos of dark matter.

The new observations and measurements provide the first direct confirmation of the so-called cold-flow model of galaxy formation.

Hotly debated since 2003, that model stands in contrast to the standard, older view of galaxy formation. The standard model said that when dark-matter halos collapse, they pull a great deal of normal matter in the form of gas along with them, heating it to extremely high temperatures. The gas then cools very slowly, providing a steady but slow supply of cold gas that can form stars in growing galaxies.

That model seemed fine until 1996, when Chuck Steidel, Caltech's Lee A. DuBridge Professor of Astronomy, discovered a distant population of galaxies producing stars at a very high rate only two billion years after the Big Bang. The standard model cannot provide the prodigious fuel supply for these rapidly forming galaxies.

The cold-flow model provided a potential solution. Theorists suggested that relatively cool gas, delivered by filaments of the cosmic web, streams directly into protogalaxies. There, it can quickly condense to form stars. Simulations show that as the gas falls in, it contains tremendous amounts of angular momentum, or spin, and forms extended rotating disks.

"That's a direct prediction of the cold-flow model, and this is exactly what we see—an extended disk with lots of angular momentum that we can measure," says Martin.

Phil Hopkins, assistant professor of theoretical astrophysics at Caltech, who was not involved in the study, finds the new discovery "very compelling."

"As a proof that a protogalaxy connected to the cosmic web exists and that we can detect it, this is really exciting," he says. "Of course, now you want to know a million things about what the gas falling into galaxies is actually doing, so I'm sure there is going to be more follow up."

Martin notes that the team has already identified two additional disks that appear to be receiving gas directly from filaments of the cosmic web in the same way.

Additional Caltech authors on the paper, "A giant protogalactic disk linked to the cosmic web," are principal research scientist Patrick Morrissey, research scientist James D. Neill, and instrument scientist Anna Moore from the Caltech Optical Observatories. J. Xavier Prochaska of UC Santa Cruz and former Caltech graduate student Daphne Chang, who is deceased, are also coauthors. The Cosmic Web Imager was funded by grants from the National Science Foundation and Caltech.

Writer: 
Kimm Fesenmaier
Writer: 
Exclude from News Hub: 
No
News Type: 
Research News
Teaser Image: 

Two Caltech Professors Named Simons Investigators

Caltech professors Alexei Kitaev and Christopher Umans have been named Simons Investigators. These appointments are given annually to "support outstanding scientists in their most productive years, when they are establishing creative new research directions." Investigators receive $100,000 annually for five years.

Alexei Kitaev, the Ronald and Maxine Linde Professor of Theoretical Physics and Mathematics, studies quantum computation and related areas of theoretical physics. He was recognized for helping to found the field of topological quantum computing, which involves theoretical computing devices that use a type of elementary particle called an anyon to do computations.

"The central idea is to protect quantum information from errors by encoding it in a collective state of many electrons called a 'topological quantum phase,'" Kitaev says. "I proposed a scheme whereby a piece of quantum information is stored in a pair of particles called Majorana modes at the ends of a microscopic wire. This idea has been elaborated by other physicists and is now being tested experimentally."

In 2012, Kitaev received the $3 million Fundamental Physics Prize for his work developing algorithms and theories to enable quantum computing. A member of Caltech's Institute for Quantum Information and Matter, he was named a MacArthur Fellow in 2008.

Chris Umans, a professor of computer science, studies complexity theory, a field that aims to determine rigorously the possibilities and limitations of computation. "Computational complexity attempts to answer the question: 'What is computationally feasible given limited computational resources?'" he says.

Umans was noted by the Simons Foundation for his work on matrix multiplication, a prominent problem that involves the devising of optimal algorithms for multiplying two n-by-n matrices. The citation also noted his development of a "novel algorithm for polynomial factorization."

"The Simons award was a complete surprise! I am honored to be recognized in this way and grateful to the Simons Foundation for their support," he says. "Long-term support like this allows researchers to really focus on difficult, long-term problems, and this is incredibly valuable, especially in these fields that are filled with deep, foundational open questions."

Umans also received an NSF CAREER award in 2004 and an Alfred P. Sloan Research Fellowship in 2005.

The Simons Foundation was founded in 1994 by Jim and Marilyn Simons to advance research in mathematics and the basic sciences. In 2012, the Simons Foundation awarded fellowships to Hirosi Ooguri, the Fred Kavli Professor of Theoretical Physics and Mathematics and Director of Caltech's Walter Burke Institute for Theoretical Physics, and former professor of astrophysics Christopher Hirata (BS '01), now a professor of physics at Ohio State University.

Writer: 
Exclude from News Hub: 
No
News Type: 
In Our Community

"Failed Stars" Host Powerful Auroral Displays

Caltech astronomers say brown dwarfs behave more like planets than stars

Brown dwarfs are relatively cool, dim objects that are difficult to detect and hard to classify. They are too massive to be planets, yet possess some planetlike characteristics; they are too small to sustain hydrogen fusion reactions at their cores, a defining characteristic of stars, yet they have starlike attributes.

By observing a brown dwarf 20 light-years away using both radio and optical telescopes, a team led by Gregg Hallinan, assistant professor of astronomy at Caltech, has found another feature that makes these so-called failed stars more like supersized planets—they host powerful auroras near their magnetic poles.

The findings appear in the July 30 issue of the journal Nature.

"We're finding that brown dwarfs are not like small stars in terms of their magnetic activity; they're like giant planets with hugely powerful auroras," says Hallinan. "If you were able to stand on the surface of the brown dwarf we observed—something you could never do because of its extremely hot temperatures and crushing surface gravity—you would sometimes be treated to a fantastic light show courtesy of auroras hundreds of thousands of times more powerful than any detected in our solar system."

In the early 2000s, astronomers began finding that brown dwarfs emit radio waves. At first, everyone assumed that the brown dwarfs were creating the radio waves in basically the same way that stars do—through the action of an extremely hot atmosphere, or corona, heated by magnetic activity near the object's surface. But brown dwarfs do not generate large flares and charged-particle emissions in the way that our sun and other stars do, so the radio emissions were surprising.

While in graduate school, in 2006, Hallinan discovered that brown dwarfs can actually pulse at radio frequencies. "We see a similar pulsing phenomenon from planets in our solar system," says Hallinan, "and that radio emission is actually due to auroras." Since then he has wondered if the radio emissions seen on brown dwarfs might be caused by auroras.

Auroral displays result when charged particles, carried by the stellar wind for example, manage to enter a planet's magnetosphere, the region where such charged particles are influenced by the planet's magnetic field. Once within the magnetosphere, those particles get accelerated along the planet's magnetic field lines to the planet's poles, where they collide with gas atoms in the atmosphere and produce the bright emissions associated with auroras.

Following his hunch, Hallinan and his colleagues conducted an extensive observation campaign of a brown dwarf called LSRJ 1835+3259, using the National Radio Astronomy Observatory's Very Large Array (VLA), the most powerful radio telescope in the world, as well as optical instruments that included Palomar's Hale Telescope and the W. M. Keck Observatory's telescopes.


This movie shows the brown dwarf, LSRJ 1835+3259, as seen with the National Radio Astronomy Observatory's Very Large Array, pulsing as a result of the process that creates powerful auroras.
Credit: Stephen Bourke/Caltech

Using the VLA they detected a bright pulse of radio waves that appeared as the brown dwarf rotated around. The object rotates every 2.84 hours, so the researchers were able to watch nearly three full rotations over the course of a single night.

Next, the astronomers used the Hale Telescope to observe that the brown dwarf varied optically on the same period as the radio pulses. Focusing on one of the spectral lines associated with excited hydrogen—the h-alpha emission line—they found that the object's brightness varied periodically.

Finally, Hallinan and his colleagues used the Keck telescopes to measure precisely the brightness of the brown dwarf over time—no simple feat given that these objects are many thousands of times fainter than our own sun. Hallinan and his team were able to establish that this hydrogen emission is a signature of auroras near the surface of the brown dwarf.

"As the electrons spiral down toward the atmosphere, they produce radio emissions, and then when they hit the atmosphere, they excite hydrogen in a process that occurs at Earth and other planets, albeit tens of thousands of times more intense," explains Hallinan. "We now know that this kind of auroral behavior is extending all the way from planets up to brown dwarfs."

In the case of brown dwarfs, charged particles cannot be driven into their magnetosphere by a stellar wind, as there is no stellar wind to do so. Hallinan says that some other source, such as an orbiting planet moving through the brown dwarf's magnetosphere, may be generating a current and producing the auroras. "But until we map the aurora accurately, we won't be able to say where it's coming from," he says.

He notes that brown dwarfs offer a convenient stepping stone to studying exoplanets, planets orbiting stars other than our own sun. "For the coolest brown dwarfs we've discovered, their atmosphere is pretty similar to what we would expect for many exoplanets, and you can actually look at a brown dwarf and study its atmosphere without having a star nearby that's a factor of a million times brighter obscuring your observations," says Hallinan.

Just as he has used measurements of radio waves to determine the strength of magnetic fields around brown dwarfs, he hopes to use the low-frequency radio observations of the newly built Owens Valley Long Wavelength Array to measure the magnetic fields of exoplanets. "That could be particularly interesting because whether or not a planet has a magnetic field may be an important factor in habitability," he says. "I'm trying to build a picture of magnetic field strength and topology and the role that magnetic fields play as we go from stars to brown dwarfs and eventually right down into the planetary regime."

The work, "Magnetospherically driven optical and radio aurorae at the end of the main sequence," was supported by funding from the National Science Foundation. Additional authors on the paper include Caltech senior postdoctoral scholar Stephen Bourke, Caltech graduate students Sebastian Pineda and Melodie Kao, Leon Harding of JPL, Stuart Littlefair of the University of Sheffield, Garret Cotter of the University of Oxford, Ray Butler of National University of Ireland, Galway, Aaron Golden of Yeshiva University, Gibor Basri of UC Berkeley, Gerry Doyle of Armagh Observatory, Svetlana Berdyugina of the Kiepenheuer Institute for Solar Physics, Alexey Kuznetsov of the Institute of Solar-Terrestrial Physics in Irkutsk, Russia, Michael Rupen of the National Radio Astronomy Observatory, and Antoaneta Antonova of Sofia University.

 

 

Writer: 
Kimm Fesenmaier
Frontpage Title: 
Powerful Auroras Shed Light On Brown Dwarfs
Writer: 
Exclude from News Hub: 
No
Short Title: 
Powerful Auroras Shed Light On Brown Dwarfs
News Type: 
Research News

$100 Million Gift from Gordon and Betty Moore Will Bolster Graduate Fellowships

Trustees Gordon (PhD '54) and Betty Moore have pledged $100 million to Caltech, the second-largest single contribution in the Institute's history. With this gift, they have created a permanent endowment and entrusted the choice of how to direct the funds to the Institute's leadership—providing lasting resources coupled with uncommon freedom.

"Those within the Institute have a much better view of what the highest priorities are than we could have," Intel Corporation cofounder Gordon Moore explains. "We'd rather turn the job of deciding where to use resources over to Caltech than try to dictate it from outside."

Applying the Moores' donation in a way that will strengthen the Institute for generations to come, Caltech's president and provost have decided to dedicate the funds to fellowships for graduate students.

"Gordon and Betty Moore's incredibly generous gift will have a transformative effect on Caltech," says President Thomas F. Rosenbaum, holder of the Institute's Sonja and William Davidow Presidential Chair and professor of physics. "Our ultimate goal is to provide fellowships for every graduate student at Caltech, to free these remarkable young scholars to pursue their interests wherever they may lead, independent of the vicissitudes of federal funding. The fellowships created by the Moores' gift will help make the Institute the destination of choice for the most original and creative scholars, students and faculty members alike."

Further multiplying the impact of the Moores' contribution, the Institute has established a program that will inspire others to contribute as well. The Gordon and Betty Moore Graduate Fellowship Match will provide one additional dollar for every two dollars pledged to endow Institute-wide fellowships. In this way, the Moores' $100 million commitment will increase fellowship support for Caltech by a total of $300 million.

Says Provost Edward M. Stolper, the Carl and Shirley Larson Provostial Chair and William E. Leonhard Professor of Geology: "Investigators across campus work with outstanding graduate students to advance discovery and to train the next generation of teachers and researchers. By supporting these students, the Moore Match will stimulate creativity and excellence in perpetuity all across Caltech. We are grateful to Gordon and Betty for allowing us the flexibility to devote their gift to this crucial priority."

The Moores describe Caltech as a one-of-a-kind institution in its ability to train budding scientists and engineers and conduct high-risk research with world-changing results—and they are committed to helping the Institute maintain that ability far into the future.

"We appreciate being able to support the best science," Gordon Moore says, "and that's something that supporting Caltech lets us do."

The couple's extraordinary philanthropy already has motivated other benefactors to follow their example, notes David L. Lee, chair of the Caltech Board of Trustees.

"The decision that Gordon and Betty made—to give such a remarkable gift, to make it perpetual through an endowment, and to remove any restrictions as to how it can be used—creates a tremendous ripple effect," Lee says. "Others have seen the Moores' confidence in Caltech and have made commitments of their own. We thank the Moores for their leadership."

The Moores consider their gift a high-leverage way of fostering scientific research at a place that is close to their hearts. Before he went on to cofound Intel, Gordon Moore earned a PhD in chemistry from Caltech.

"It's been a long-term association that has served me well," he says.

Joining him in Pasadena just a day after the two were married, Betty Moore became active in the campus community as well. A graduate of San Jose State College's journalism program, she secured a job at the Ford Foundation's new Pasadena headquarters and also made time to come to campus to participate in community activities, including the Chem Wives social club.

"We started out at Caltech," she recalls. "I had a feeling that it was home away from home. It gives you a down-home feeling when you're young and just taking off from family. You need that connection somehow."

After earning his PhD from Caltech in 1954, Gordon Moore took a position conducting basic research at the Applied Physics Laboratory at Johns Hopkins University. Fourteen years and two jobs later, he and his colleague Robert Noyce cofounded Intel Corp. Moore served as executive vice president of the company until 1975, when he took the helm. Under his leadership—as chief executive officer (1975 to 1987) and chairman of the board (1987 to 1997)—Intel grew from a Mountain View-based startup to a giant of Silicon Valley, worth more than $140 billion today.

Moore is widely known for "Moore's Law," his 1965 prediction that the number of transistors that can fit on a chip would double every year. Still relevant 50 years later, this principle pushed Moore and his company—and the tech industry as a whole—to produce continually more powerful and cheaper semiconductor chips.

Gordon Moore joined the Caltech Board of Trustees in 1983 and served as chair from 1993 to 2000. That same year, he and his wife established the Gordon and Betty Moore Foundation, an organization dedicated to creating positive outcomes for future generations in the San Francisco Bay Area and around the world.

Among numerous other honors, Gordon Moore is a member of the National Academy of Engineering, a fellow of the Institute of Electrical and Electronics Engineers, and a recipient of the National Medal of Technology and the Presidential Medal of Freedom. 

The Gordon and Betty Moore Graduate Fellowship Match is available for new gifts and pledges to endow graduate fellowships. For more information about the match and how to support graduate education at Caltech, please contact Jon Paparsenos, executive director of development, at (626) 395-3088 or jpapars@caltech.edu.

Exclude from News Hub: 
No
News Type: 
In Our Community

Clean Water For Nepal

On the steep, tea-covered hillsides of Ilam in eastern Nepal, where 25 percent of households live below the poverty level and electricity is scarce, clean running water is scarcer still. What comes out of the region's centralized distribution systems is unfiltered, untreated, and teeming with nitrates, viruses, and E. coli. Purifying it is the consumer's responsibility.

But wood and yak dung, the only available fuels for boiling water, are precious, and purification tablets impart an unpleasant chlorine taste. The result? During the rainy season, local hospitals overflow with typhoid and gastrointestinal cases, mostly involving children and tainted runoff.

That may change, thanks to a gravity flow and slow-sand filtration system designed by Caltech undergraduates. They represent EWB-Caltech, one of the newest chapters of Engineers Without Borders USA, a nongovernmental organization (NGO) whose mission is to design and implement sustainable engineering projects in underprivileged communities.

Founded in 2012 by Sarah Wright (BS '13, bioengineering), EWB-Caltech already has about 30 members. This summer, a half dozen of the chapter's members are traveling to Ilam, where they are staying with local villagers while helping to oversee and implement the system's construction. The hillside will be partly excavated and then reconstructed. Layers of rock, gravel, sand, polyethylene sheeting, and soil will soak up rainfall, filtering and purifying it as it trickles into underground water. Pipes tapping into the underground water will run downhill to a small communal enclosure made of poured concrete, providing a reliable supply of clean water for about 100 households, with another 200 indirectly affected.

The students will not be working alone, says their mentor, environmental engineering consultant Gordon Treweek (MS '71, PhD '75) who is partnering with Caltech engineering students for the first time. "All EWB projects are community-driven, with the local workforce providing much of the labor. And we've received tremendous logistical support, including interpreters, from the Namsaling Community Development Center, an NGO in Ilam that had previously worked with an EWB chapter from the University of Colorado, Boulder."

According to EWB requirements the Nepalese must contribute 5 percent of the project's budget. EWB-Caltech copresidents Jihoon Lee (a senior in bioengineering) and Nauman Javed (a senior in physics) acknowledge that successfully coming up with the remainder—over $20,000—involved nearly continuous fund-raising. "We've been applying for grants, soliciting private donations, partnering with companies, especially water-related and environmental corporations, and we held a benefit dinner in January that was largely attended by Caltech faculty and friends," says Lee.

Both a 10-day on-site assessment trip last summer and this summer's trip were covered by individual donations and grants. The assessment trip took Treweek, Javed, and fellow Caltech senior Webster Guan (chemical engineering) to Ilam to meet with the NGO; to survey the local community of about 100 families to ascertain their needs and willingness to assist in the construction and ongoing maintenance of the water tap stand; and to gather predesign data for planning construction and estimating costs.

"The support we have received from Caltech alumni directly and through their networks of contacts at Northrop Grumman and Boeing has been invaluable in helping to keep this project moving forward," Treweek says.

After the assessment trip, the students spent the 2014–15 school year preparing detailed engineering documents using computer-aided design techniques. In this, they were assisted by the water-resource engineering firms Carollo Engineers and Montgomery Watson Harza, whose pro bono involvement did not surprise Treweek. "Consulting engineering firms frequently donate resources for projects like this," he says. "It's socially responsible, and it gives them a chance to observe future engineers addressing the four traditional phases of engineering: planning, design, fund-raising, and construction."

With preventable infectious diseases a leading component of Ilam's one-in-three infant mortality rate, the project includes a public-education component. "Besides training the local villagers who will maintain our spring-water source protection system," says Javed, "we plan to visit local schools, demonstrate how the system works, teach a little germ theory."

But no amount of careful planning can guarantee success. Similar projects have failed due to engineering problems, misaligned long-term governance strategies, eleventh-hour reprioritizations by the community, even simple miscommunication. "We've drafted plenty of contingency plans," affirms Lee, "with great support from EWB-USA. Their stringent review procedures covered every engineering and social aspect of the project, and they've given us detailed feedback on our drawings, schedules, and rationales."

After the implementation phase—which ends just one week before classes resume back in Pasadena—EWB-Caltech will continue to monitor the site for five to six years. By then the current members will have moved on and a new group of student leaders will have taken over this project. But for now, they are spending their summer trying to build a better world, drop by drop.

Writer: 
Exclude from News Hub: 
No
News Type: 
In Our Community

Pages

Subscribe to RSS - PMA