Caltech astronomer elected president of the American Astronomical Society

PASADENA—Anneila Sargent, professor of astronomy at the California Institute of Technology and director of Caltech's Owens Valley Radio Observatory, has been elected president of the American Astronomical Society (AAS).

Her term of office as president-elect will begin in June, and she will serve as president from June 2000 to June 2002, said AAS spokesperson Steve Maran.

Sargent, a native of Scotland, is an authority on star formation in the Milky Way and other galaxies. Most recently she has been investigating the way in which stars like the sun are created and evolve.

With her collaborators and postdoctoral scholars, she uses the Owens Valley millimeter-wave array, and the Keck Telescopes on Mauna Kea, Hawaii, to search for and study other potential planetary systems. Her interests range from the earliest stages of star formation, when dense cores in interstellar clouds collapse to form stars, to the epochs when individual planets may be born. This field has garnered considerable interest within the scientific community, as well as from the news media and the general public, because of the possibility of locating other worlds outside the solar system.

Sargent cochaired a 1996 workshop at the request of the White House Office of Science and Technology Policy to assess the major questions of space science and how U.S. programs can promote discovery to address those questions, and to plan for future steps in space exploration and research. Titled "The Search for Origins," the workshop report summarized the findings of three dozen of the leading biologists, planetary scientists, astronomers, and cosmologists in the country, and led to a workshop headed by Vice President Al Gore.

Currently, she is also a member of the Board of Associated Universities Inc., the Space Telescope Institute Council, and the National Research Council's decadal astronomy and astrophysics survey committee.

She was also a member of the 1995 Gordon Conference on the Origins of Solar Systems, the 1995 blue-ribbon panel on NASA's proposed exploration of neighboring planetary systems, and the 1993 National Research Council's committee on astronomy and astrophysics, and she was vice-chair of the 1993 NRC task group on the SIRTF and SOFIA infrared space missions.

Born in Kirkcaldy, Fife, Scotland, Sargent earned her bachelor of science degree with honors in physics from the University of Edinburgh. After completing her doctorate in astronomy at Caltech in 1977, she joined the Institute as a research fellow in astronomy, and as a member of the professional staff. She was appointed a senior research fellow in 1988, and a senior research associate in 1990.

She was named associate director of the Owens Valley Radio Observatory in 1992, became executive director in 1996, and director in 1998. During the same year, she was also appointed a professor of astronomy.

Her major honors include the 1998 NASA Public Service Medal, which she was awarded in part for her work on the Space Science Advisory Committee and as a member of the NASA Council. Her Caltech honors include the 1998 Woman of the Year award. She is married to Wallace Sargent, who is also a Caltech professor of astronomy, and director of Palomar Observatory. The Sargents have two daughters, Lindsay Sargent and Alison Hubbs.

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New electron states observed by Caltech physicists

PASADENA—Caltech physicists have succeeded in forcing electrons to flow in an unusual way never previously observed in nature or in the lab.

According to James Eisenstein, professor of physics, he and his collaborators have observed electrons that, when confined to a two-dimensional plane and subjected to an intense magnetic field, can apparently tell the difference between "north-south" and "east-west" directions in their otherwise featureless environment. As such, the electrons are in a state very different from that of conventional isotropic solids, liquids, and gases.

"Electrons do bizarre and wonderful things in a magnetic field," says Eisenstein, explaining that electrons are elementary particles that naturally repel each other unless forced together.

By trapping billions of electrons on a flat surface within a semiconductor crystal wafer—and thus limiting them to two dimensions—Eisenstein's team is able to study what the electrons do at temperatures close to absolute zero and in the presence of large perpendicular magnetic fields.

Research on exotic states of electrons is relatively new, but its theoretical history goes back to the 1930s, when Eugene Wigner speculated that electrons in certain circumstances could actually form a sort of crystallized solid. It turns out that forcing electrons to lie in a two-dimensional plane increases the chances for such exotic configurations.

"They cannot get out of one another's way into the third dimension, and this actually increases the likelihood of unusual 'correlated' phases," Eisenstein says. Adding a magnetic field has a similar effect by forcing the electrons to move in tiny circular orbits rather than running unimpeded across the plane.

One of the best examples of the strange behavior of two-dimensional electron systems is the fractional quantum Hall effect, for which three American scientists won the Nobel Prize in physics last year. Electrons in such a system are essentially a liquid, and since the quantum effects of the subatomic world become a factor at such scales, the entire group takes on some unusual electrical properties.

Eisenstein's new findings are very different than the fractional quantum Hall effect. Most importantly, his group has found that a current sent one way through the flat plane of electrons tends to encounter much greater resistance than an equal current sent at a perpendicular angle. Normally, one would expect all the electrons to more or less disperse evenly across the flat plane, which would mean the same resistance for a current flowing at varying angles.

Dramatically, this "anisotropy" only sets in when the temperature of the electrons is reduced to within one-tenth of one degree above absolute zero, the lowest temperature a system can attain.

Owing to the laws of quantum mechanics, the circular orbits of the electrons exist only at discrete energies, called Landau levels. For the fractional quantum Hall effect, all of the electrons are in the lowest such level. Eisenstein's new results appear when the higher energy levels are also populated with electrons. While it appears that a minimum of three levels must be occupied, Eisenstein has seen the effects in many higher Landau levels.

"This generic aspect makes the new findings all the more important," comments Eisenstein.

One scheme that might explain the new results is that the electrons are accumulated into long ribbons. Physically, the system would somewhat resemble lines of billiard balls lying in parallel rows on a pool table. If this is what is happening, the Coulomb repulsion of the electrons is overwhelmed within the ribbons so that the electrons can cram more closely together, while in the spaces between the ribbons the number of electrons is reduced.

"There's not a good theoretical understanding of what's going on," Eisenstein says. "Some think such a 'charge-density wave' is at the heart; others think a more appropriate analogy might be the liquid crystal displays in a digital watch."

Another interesting question that could have deep underpinnings is how and why the system "chooses" its particular alignments. The alignment could have to do with the crystal substrate in the wafer, but Eisenstein says this is not clear.

Eisenstein and his collaborators are proceeding with their work, and have recently published results in the January 11 issue of the journal Physical Review Letters.

Heavily involved in the work are Mike Lilly, a Caltech postdoctoral scholar; and Ken Cooper, a Caltech graduate student in physics. Loren Pfeiffer and Ken West—both of Bell Laboratories, Lucent Technologies in Murray Hill, New Jersey—contribute the essential high-purity semiconductor wafers used in the experiments.

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David Goodstein Awarded 1999 Oersted Medal

PASADENA—The California Institute of Technology is pleased to announce that David Goodstein has been awarded the 1999 Oersted Medal by the American Association of Physics Teachers. The medal is to be presented at the Association's annual meeting in Anaheim next year.

Goodstein is vice provost and professor of physics and applied physics at Caltech, where he has been on the faculty for more than 30 years. In 1995 he was named the Frank J. Gilloon Distinguished Teaching and Service Professor.

His book, States of Matter, published in 1975 by Prentice Hall and reissued by Dover Press in 1985, was hailed by Physics Today as the book that launched a new discipline, condensed-matter physics. His research in experimental condensed-matter physics has dealt with phases and phase transitions in adsorbed, two-dimensional matter, ballistic phonons in solids, superfluidity in liquid helium, and critical point phenomena. This work has led to nearly 200 scientific publications. He is currently working on a future flight experiment that will examine the dynamics of the superfluid phase transition in the absence of gravity.

Goodstein has served on numerous scientific and academic panels, currently including the national advisory committee to the mathematical and physical sciences directorate of the National Science Foundation, which he currently chairs. He is a founding member of the board of directors of the California Council on Science and Technology.

Goodstein was the host and project director of The Mechanical Universe, a 52-part college physics telecourse based on his popular lectures at Caltech. The project, which has been adapted for high-school use and translated into many other languages, has been broadcast on hundreds of public-broadcasting stations and has garnered more than a dozen prestigious awards, including the 1987 Japan Prize for television.

In recent times, Goodstein has become interested in some of the larger issues that affect science as a profession. In a series of articles, colloquia, and speeches, he has stressed and analyzed the profound changes that became inevitable in the last few decades as the long period of exponential expansion of science came to an end. He has also turned his attention to issues related to conduct and misconduct in science. Prompted by the need to compose a set of regulations governing possible misconduct at Caltech, he has developed an academic subspecialty in this area, writing and speaking about it in a variety of forums. Together with his colleague, Professor of Philosophy James Woodward, he has developed a course, Research Ethics, which has been taught each year at Caltech since the early 1990s.

Born in Brooklyn, New York, Goodstein attended Brooklyn College and received his PhD in physics from the University of Washington. He lives in Pasadena with his wife, Dr. Judith R. Goodstein, who is a faculty associate in history at Caltech, where she serves as archivist and registrar. The Goodsteins have two grown children and two grandchildren and have recently coauthored a best-selling book, Feynman's Lost Lecture.

The Oersted Medal, established in 1936, is the most prestigious award of the American Association of Physics Teachers and recognizes a teacher for notable contributions to the teaching of physics. A monetary award of $5,000, an inscribed medal, and a certificate are presented to the winner. There have been two previous Caltech winners of the Oersted Medal: Robert A. Milliken in 1940 and Richard P. Feynman in 1972.

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Caltech physicists achieve first bona fide quantum teleportation

PASADENA—Physicists at the California Institute of Technology, joined by an international collaboration, have succeeded in the first true teleportation of a quantum state.

In the October 23 issue of the journal Science, Caltech physics professor H. Jeff Kimble and his colleagues write of their success in transporting a quantum state of light from one side of an optical bench to the other without it traversing any physical medium in between.

In this sense, quantum teleportation is similar to the far-fetched "transporter" technology used in the television series Star Trek. In place of the actual propagation of a light beam, teleportation makes use of a delicate quantum mechanical phenomenon known as "quantum entanglement," the quintessential ingredient in the emerging field of quantum information science.

"In our case the distance was only a meter, but the scheme would work just as well over much larger distances," says Professor Samuel Braunstein, a coauthor from the University of Wales in Bangor, United Kingdom, who, with Kimble, conceived the scheme. "Our work is an important step toward the realization of networks for distributing quantum information—a kind of 'quantum Internet.'"

Teleportation of this kind was first proposed theoretically by IBM scientist Charles H. Bennett and colleagues in 1993. The Caltech experiment represents the first time quantum teleportation has actually been performed with a high degree of "fidelity." The fidelity describes how well a receiver, "Bob," can reproduce quantum states from a sender, "Alice."

Although quantum teleportation was recently announced by two independent labs in Europe, neither experiment achieved a fidelity that unambiguously required the use of quantum entanglement between Alice and Bob.

"True quantum teleportation involves an unknown quantum state entering Alice's apparatus and a similar unknown state emerging from Bob's remote station," says Kimble. "Moreover, the similarity of input and output, as quantified by the fidelity, must exceed that which would be possible if Alice and Bob only communicated by classical means—for instance, by normal telephone wiring.

"Although there has been wonderful progress in the field, until now there has not been an actual demonstration of teleportation that meets these criteria."

In the experiment, the Caltech team generated exotic forms of light known as "squeezed vacua," which are split in such a way that Alice and Bob each receive a beam that is the quantum mechanical "twin" of the other. These EPR beams, named after the historic Einstein-Podolsky-Rosen (EPR) paradox of 1935, are among the strangest of the predictions of quantum mechanics. It was their theoretical possibility that led Einstein to reject the idea that quantum mechanics might be a fundamental physical law.

A trademark of quantum mechanics is that the very act of measurement limits the controllability of light in ways not observed in the macroscopic world: even the most delicate measurements can cause uncontrollable disturbances. Nevertheless, in certain circumstances, these restrictions can be exploited to do things that were unimaginable in classical physics.

Here, photons from the EPR beams delivered to Alice and Bob can share information that has no independent existence in either beam alone. Through this "entanglement," the act of measurement in one place can influence the quantum state of light in another.

Once Alice and Bob have received their spatially separate but entangled components of the EPR beams, Alice performs certain joint measurements on the light beam she wishes to teleport together with her half of the EPR "twins." This destroys the input beam, but she then sends her measurement outcomes to Bob via a "classical" communication channel. Bob uses this classical information to transform his component of the EPR beam into an output beam that closely mimics the input to Alice, resurrecting at a distance the original unknown quantum state.

A unique feature of Kimble's experiment is a third party called "Victor," who "verifies" various aspects of the protocol performed by Alice and Bob. It is Victor who generates and sends an input to Alice for teleportation, and who afterward inspects the output from Bob to judge its fidelity with the original input.

"The situation is akin to having a sort of 'quantum' telephone company managed by Alice and Bob," says Kimble. "Having opened an account with an agreed upon protocol, a customer (here Victor) utilizes the services of Alice and Bob unconditionally for the teleportation of quantum states without revealing these states to the company. Victor can further perform an independent assessment of the 'quality' of the service provided by Alice and Bob."

The experiment by the Kimble group shows that the strange "connections" between entities in the quantum realm can be gainfully employed for tasks that have no counterpart in the classical world known to our senses.

"Taking quantum teleportation from a purely theoretical concept to an actual experiment brings the quantum world a little closer to our everyday lives," says Christopher Fuchs, a Prize Postdoctoral Scholar at Caltech and a coauthor. "Since the earliest days of the theory, physicists have treated the quantum world as a great mystery. Maybe making it part of our everyday business is just what's been needed for making a little sense of it."

This demonstration of teleportation follows other work the Kimble group has done in recent years, including the first results showing that individual photons can strongly interact to form a quantum logic gate. Kimble's work suggests that the quantum nature of light may someday be exploited for building a quantum computer, a machine that would in certain applications have computational power vastly superior to that of present-day "classical" computers.

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Tom Apostol Wins Trevor Evans Award

PASADENA—Dr. Tom Apostol, professor emeritus of mathematics and project director of Project MATHEMATICS! at the California Institute of Technology, was recently named a recipient of the Trevor Evans award by the Mathematical Association of America.

Apostol was awarded the prize in recognition of his article "What Is the Most Surprising Result in Mathematics? (Part II)" (Math Horizons, February 1997).

According to the award citation, the answer to Apostol's question is "the Prime Number Theorem. At least that is the answer so convincingly argued by Tom Apostol in this information-rich yet easily digestible article. The article traces the history of the theorem and shows how the riddle of the distribution of the primes drove Euler, Riemann, and many others to unearth fertile new areas of mathematics. Apostol reminds us that deep ideas can always be made accessible to young minds—you just have to try hard enough."

Apostol received a BS (1944) and an MS (1946) from the University of Washington, and a PhD (1948) from the University of California, Berkeley. He has been a professor at Caltech since 1950.

Established in 1992, the Trevor Evans awards, consisting of a citation and cash prize, are presented by the Mathematical Association of America to authors of exceptional articles that are accessible to undergraduates and published in Math Horizons.

The Mathematical Association of America (MAA) is the world's largest organization devoted to mathematics education at the collegiate level. The nearly 30,000 members of the MAA participate in a variety of activities that foster mathematics education, professional development, student involvement, and public policy. MAA's national focus is complemented by its 29 regional sections—together functioning as an extensive network for the mathematics community.

Founded in 1891, Caltech has an enrollment of some 2,000 students, and a faculty of about 280 professorial faculty and 130 research faculty. The Institute has more than 19,000 alumni. Caltech employs a staff of more than 1,700 on campus and 5,300 at JPL.

Over the years, 26 Nobel Prizes and four Crafoord Prizes have been awarded to faculty members and alumni. Forty-three Caltech faculty members and alumni have received the National Medal of Science; and eight alumni (two of whom are also trustees), two additional trustees, and one faculty member have won the National Medal of Technology. Since 1958, 13 faculty members have received the annual California Scientist of the Year award. On the Caltech faculty there are 75 fellows of the American Academy of Arts and Sciences; and on the faculty and Board of Trustees, 68 members of the National Academy of Sciences and 46 members of the National Academy of Engineering.

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Thomas Tombrello named Caltech PMA division chair

PASADENA—The California Institute of Technology Board of Trustees has approved the appointment of physics professor Thomas A. Tombrello chair of the Division of Physics, Mathematics and Astronomy.

Tombrello's appointment becomes effective August 1, 1998, according to Caltech president David Baltimore.

"Tom Tombrello has demonstrated remarkable abilities in both research and administration through the years," Baltimore said. "Not only does he pursue a huge variety of interests, but he is also equally at home with basic and applied research.

"He's the ideal person to lead the division into the 21st century."

Tombrello and his research group are primarily involved in applying the techniques of theoretical and experimental physics to problems in materials science, surface physics, and planetary science. His ongoing research includes understanding the damage processes caused by megavolt ions in solids, characterizing the sputtering of materials by low-energy ions, and growing and studying novel light-emitting materials.

A native of Texas, Tombrello was born in Austin, grew up in Dallas, and earned his BA, MA, and PhD degrees at Rice University in Houston.

Tombrello came to Caltech in 1961, and except for a brief stint on the Yale faculty, has been here ever since. A full professor of physics since 1971, he also served as vice president and director of research at Schlumberger-Doll Research from 1987 to 1989. He was named William R. Kenan Jr. Professor at Caltech in 1997.

As chair of the Division of Physics, Mathematics and Astronomy, he will oversee a department that has long been acclaimed for groundbreaking research and outstanding faculty. The department's list of Nobel laureates includes Robert A. Millikan, who measured the charge of the electron; Carl Anderson, who discovered the positron and thus demonstrated the existence of antimatter; Richard Feynman, who revolutionized the theory of quantum electrodynamics with his Feynman diagrams; Murray Gell-Mann, who first predicted the existence of the quark as well as the quantum concept of strangeness; and William A. Fowler, who was one of the founders of the field of nuclear astrophysics.

Tombrello said that his immediate goals will be to strengthen the Division's efforts in theoretical physics, mathematics, and observational astronomy.

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Physics student wins acclaim for new theory of neutron-star spin

PASADENA--When you're beginning a career in cosmology, it's only fitting to start with a bang.

That's what Ben Owen will do now that he has his doctorate in physics from the California Institute of Technology. Not only did Owen win the annual Clauser Prize for the best Caltech dissertation at the June 12 commencement, but his work has also been the subject of an international symposium. In September, he'll fly to Germany for a new job at the Albert Einstein Institute (where the symposium was held) as a postdoctoral researcher.

The reason Owen's dissertation has stirred so much interest is that it solves a nagging, decades-old question in astrophysics and opens up vistas of new questions.

In particular, chapter 5 of his "Gravitational Waves from Compact Objects" shows why young neutron stars have such slow spins. The research of chapter 5, which was done with Lee Lindblom and Sharon Morsink, predicts that rapidly spinning, newborn neutron stars will pulsate wildly, throwing off their spin energy as gravitational waves. The work appears in the June 1 issue of the journal Physical Review Letters.

The new theory of Owen and his colleagues will be tested experimentally in a few years, after the Laser Interferometer Gravitational-Wave Observatory (LIGO) comes on-line.

Neutron stars are extremely compact bodies about the mass of the sun, packed into a sphere about 15 miles in diameter. They are typically formed in the supernova explosions of massive stars.

Because the fusion of lighter elements in the star has ceased, the material remaining after the explosion scrunches together so closely that the electrons and protons of most of its atoms actually fuse together to form neutrons—and thus the name.

Neutron stars are not so compact as black holes, which are regions so dense that not even light can escape. But neutron stars are still compact enough to generate some bizarre effects. If an astronaut landed on a neutron star, for example, both he and his spaceship would be smeared by gravity into an even layer of just a few atoms over the entire surface of the star.

Also, neutron stars are noteworthy for their tendency to spin like crazy. Astronomers on Earth infer this spin from a telltale "blinking" in radio signals or sometimes even in a strobelike blinking in visible light. Based on the rate of blinking, observers know that these particular neutron stars—known as pulsars—can spin as rapidly as 600 times per second.

But this is where the controversy comes in and where Owen's dissertation is stirring up so much interest. Based on the laws of Newtonian physics, there's no compelling reason why a slowly rotating normal star shouldn't speed up to the fastest rotation rate possible once it goes supernova and then collapses into a neutron star.

The same effect can be seen in an ice skater who pulls in her arms to rotate faster while spinning.

But all of the young neutron stars observed by astronomers spin at 120 revolutions per second or less—a factor of five slower than the fastest known pulsar, which is very old and is thought to have been spun up long after the supernova by other mechanisms.

Owen's theory is that a type of fluid circulation occurs on the neutron stars that creates a sort of drag in space-time. Called "r-modes" because they owe their existence to rotation, these motions look much like the ocean eddies that move currents in circular motions on Earth.

What Owen's dissertation has shown is that the r-modes of a rapidly rotating neutron star strongly emit gravitational waves. The drag effect, caused by the gravitational waves leaving the star, in turn causes the r-modes to grow when they would normally die away due to the internal friction found in young neutron stars. In the process, this forces the spinning neutron star to slow down.

Thus, newly created neutron stars can indeed start their lives spinning quite rapidly, but are quickly slowed down by the growing r-modes. Old neutron stars have much stronger friction and can be spun up again by other processes.

"The standard methods known right now say that these currents could grow very large," says Owen.

The size of the r-modes is the key, he explains. His work shows that, if an r-mode were to be so large that it sloshed material virtually from pole to pole, the neutron star should slow down to one-tenth its original rate of rotation within a year. This, in fact, conforms to the rates of rotation seen in existing pulsars.

But the effect is a self-defeating one, Owen says. The r-modes are kept going by gravitational waves, which are stronger when emitted by rapidly rotating stars. But the gravitational waves leaving the star cause it to spin down, which makes the waves weaker, which in turn means there is less power to keep the r-modes going. So the neutron star eventually reaches an equilibrium.

"If the r-modes get very large, they'll start radiating a lot of energy as gravitational waves," Owen says. "But they can't do that forever, because the rotational energy they're radiating is what keeps them alive in the first place."

So in the course of a year, Owen shows, just about any pulsar should be spun down to a rotation rate much less than the Newtonian maximum.

Owen's work is purely theoretical at this point, but could be tested when LIGO is operational. LIGO, a collaborative project between Caltech and MIT with twin detectors in southern Louisiana and central Washington, is designed expressly for the detection and detailed study of gravitational waves.

If a supernova goes off in our cosmic neighborhood-say, within 60 million light-years-LIGO should be able to detect the gravitational waves thrown toward Earth. And if the waves change at the predicted rate over the course of a year, Owen's theoretical work will be borne out by observation.

"Several supernovae should go off every year at a distance close enough for LIGO to detect the waves," he says. "So when a supernova occurs, we should first see the waves start very abruptly at up to 1,000 cycles per second, and then chirp down to about 100 to 200 cycles per second over the course of a year."

The work of Owen, Lindblom and Morsink raises a vista of new questions, with which cosmologists and gravity-wave experimenters world-wide are now struggling. Just how large does the sloshing in a young neutron star get, and what limits its growth? Can LIGO experimenters redesign their computer programs to find Owen's predicted waves in LIGO's plethora of data? What other kinds of stars will slosh wildly, like Owen's newborn neutron stars, and what will that sloshing do to them, and can LIGO be tuned to find their gravitational waves?

Owen's thesis supervisor at Caltech was Kip Thorne, a renowned theoretical physicist who is author of the popular book Black Holes and Time Warps: Einstein's Outrageous Legacy.

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Gamma-ray Burst Found To Be Most Energetic Event in Universe

PASADENA—A team of astronomers from the California Institute of Technology announced today that a recently detected cosmic gamma-ray burst was as bright as the rest of the universe, releasing a hundred times more energy than previously theorized.

The team has measured the distance to a faint galaxy from which the burst, designated GRB 971214, originated. It is about 12 billion light-years from Earth (one light-year is approximately 5.9 trillion miles.) Combined with the observed brightness of the burst, this large distance implies an enormous energy release. The team's findings appear in the May 7 issue of the scientific journal Nature.

"The energy released by this burst in its first few seconds staggers the imagination," said Caltech professor Shrinivas Kulkarni, one of the two principal investigators on the team. The burst appears to have released several hundred times more energy than an exploding star, called a supernova, until now the most energetic known phenomenon in the universe.

"For about one or two seconds, this burst was as luminous as all the rest of the entire universe," said Caltech professor George Djorgovski, the other principal investigator on the team.

Finding such a large energy release over such a brief period of time is unprecedented in astronomy, except for the Big Bang itself.

"In a region about a hundred miles across, the burst created conditions like those in the early universe, about one millisecond [1/1,000 of a second] direction in the sky: unlike visible light, gamma-rays are exceedingly difficult to observe with a telescope, and the bursts' short duration exacerbates the problem. The Italian/Dutch satellite BeppoSAX, launched in 1996, had the ability to localize the bursts on the celestial sphere with a sufficient precision to permit follow-up observations with the world's most powerful ground-based telescopes.

The image shows the same field as seen about two months later, after the burst afterglow has faded away, revealing a faint galaxy at its position (also marked with an arrow).

This breakthrough led to the discovery of long-lived "afterglows" of bursts in X-rays, visible and infrared light, and radio waves. While gamma-ray bursts last only a few seconds, their afterglows can be studied for several months. This, in turn, led to the discovery that the bursts do not originate within our own galaxy, the Milky Way, but rather are associated with high-redshift, extremely distant galaxies in the universe.

The gamma-ray burst was detected on December 14, 1997, by the BeppoSAX and CGRO satellites. BeppoSAX and NASA's Rossi X-ray Timing Explorer spacecraft detected an X-ray afterglow. BeppoSAX precision led to the detection of a visible light afterglow, found by a team from Columbia University and Dartmouth College, including Professors Jules Halpern, David Helfand, John Torstensen, and their collaborators, using a 2.4-meter telescope at Kitt Peak, Az., but no distance could be measured from these observations.

As the visible light from the burst afterglow faded, the Caltech team detected an extremely faint galaxy at its location, using one of the world's largest telescopes, Caltech's W. M. Keck Observatory's 10-meter Keck II telescope, on Mauna Kea, Hawaii. The galaxy is about as faint as an ordinary 100-watt light bulb would be as seen from a distance of a million miles.

Subsequent images taken with the Hubble Space Telescope confirmed the association of the burst afterglow with this faint galaxy.

The Caltech team succeeded in measuring the distance to this galaxy, using the light-gathering power of the Keck II telescope. The galaxy is at a redshift of z=3.4, or about 12 billion light-years distant (assuming the universe to be about 14 billion years old).

From the distance and the observed brightness of the burst, astronomers derived the amount of energy released in the flash. Although the burst only lasted a few seconds, the energy released was hundreds of times larger than the energy given out in supernova explosions, and it is about equal to the amount of energy radiated by our entire galaxy over a period of a couple of centuries.

This is only the energy seen in the gamma rays. It is possible that other forms of radiation, such as neutrinos or gravity waves, which are extremely difficult to detect, carried a hundred times more energy than that.

While the origin of the bursts remains a mystery, what happens to the burst's glowing remnant appears to be reasonably well understood, within the so-called cosmic-fireball model. The observations of the burst afterglow by the Caltech team helped determine in some detail its physical parameters.

"It is gratifying to see that we do have some theoretical understanding of this remarkable phenomenon," said Kulkarni.

In addition to Professors Kulkarni and Djorgovski, the team includes Dr. Dale Frail from the National Radio Astronomy Observatory in Socorro, New Mexico; Drs. A. N. Ramaprakash, Tom Kundic, Stephen Odewahn, and Lori Lubin from Caltech; Dr. Mark Dickinson from the Johns Hopkins University, in Baltimore, Maryland; Dr. Robert Goodrich from the W. M. Keck Observatory in Hawaii; graduate students Joshua Bloom and Kurt Adelberger from Caltech; and many others.

Full scale images of the GRB 971214 field are available.

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Physicists create first nanometer-scale mechanical charge detector

PASADENA—Wristwatch cellular phones and space probes the size of baseballs would certainly have some eager customers, but both are still the stuff of science fiction.

Nonetheless, physicists are making strides these days in the sort of miniaturization that could someday make tiny electromechanical devices a reality. One such milestone, the first nanometer-scale mechanical charge detector, is reported in the current issue of Nature.

According to Michael Roukes, professor of physics at Caltech and coinventor of the device, the new electrometer is among the most sensitive charge detectors in existence, and definitely the first based upon nanomechanical principles.

"One compelling reason for doing this sort of thing is to explore entirely new avenues for making small, ultralow power electronic devices," says Roukes.

"Making new types of electronic devices that involve moving elements, which we call nanoelectromechanical systems, will open up a huge variety of new technological applications in areas such as telecommunications, computation, magnetic resonance imaging, and space exploration. And the physics is exciting, besides."

The device fabricated at Caltech by Roukes and his former postdoctoral collaborator, Andrew Cleland (now an assistant professor at UC Santa Barbara), is a good example of the type of advances in solid-state devices that currently are loosely gathered these days under the rubric "nanotechnology." Roukes says he generally avoids using the term. "Rather, this is the kind of science that is building the foundation for real nanotechnology, not the stuff of fiction. Right now Mother Nature is really the only true nanotechnologist."

A nanometer is one-billionth of a meter, which is about a hundred-thousandth the width of a human hair. A few atoms stacked side-by-side span about a nanometer.

To give an idea of the scale, Roukes points out that the devices are far smaller than cellular organisms; a clear picture of the device's inner workings can only be taken with an electron microscope.

The scale is especially noteworthy when one considers that the electrometer is actually a mechanical device, in the same manner as an old-fashioned clock. In other words, there are moving parts at its heart. In the Caltech devices, movement is induced by tiny wires that exert forces on the nanomechanical elements when a minute external electrical current is applied to them.

"The simplest kinds of mechanical structures are resonators, for example, cantilevers—in other words, a structure like a diving board—or thin clamped beams, something like a thick guitar string attached at both ends," Roukes explains. "They really are mechanical structures—you 'pluck' them to get them to vibrate."

"What's fascinating is that, if you can get these things small enough, they'll vibrate billions of times per second—which gives them the same frequency as the microwaves used in telecommunications," he says. "That's because their mass is very small, which means there's less inertia for internal forces to overcome.

There is a second important aspect to nanomechanical systems, Roukes adds. "Because the distances involved are very small, the amplitudes of their vibrations are very small. For this reason, the amount of energy you would have to put into such devices to get them going is extremely minute.

"This means that for certain critical applications—like small communicators and miniaturized satellites—you would not have to carry along nearly as much energy to run the device."

The latter would be fortuitous in any circumstances where carrying along power is difficult. Transistors in the best receiving devices today can run on a few thousandths of a watt, but with nanotechnology, they could run on a few billionths of a watt, or less. Thus, planetary space probes (which employ such devices in spades) could be much smaller, since they could get by with a much smaller energy source.

At the center of the Caltech nanoelectromechanical charge detection device are small rods that vibrate something like a nanoscale tuning fork. In their ultimate incarnation, which Roukes believes his lab can achieve in the next few years, these rods will be about 100 nanometers long, 10 nanometers wide, and 10 nanometers thick.

Roukes indicates that a silicon beam of such small dimensions would vibrate at about 7 gigahertz (or 7 billion times per second) if it is clamped down at both ends. When one considers that a top-of-the-line personal computer these days has a clock speed about twenty times slower, the advantages become apparent.

But it's not necessarily the replacement of conventional computer components that Roukes is after. It turns out that the small resonators his group is currently able to manufacture on campus—if cooled to temperatures a few tenths of a degree above absolute zero—sit right at the border where the quantum effects governing individual atoms and particles take over.

Working with these quantum effects is a daunting technological challenge, but success could lead to devices such as quantum computers.

"There is a natural dividing line that depends on the temperature and the frequency. Basically, if you can get the temperature low enough and the frequency is high enough, then you can operate at the quantum level.

"We could do this today," Roukes says. "In my laboratories we can get to temperatures a few thousandths of a degree above absolute zero. We also have the sizes small enough to give us sufficiently high frequencies.

"But what we don't yet know how to do is to probe these structures optimally."

In fact, one of the main themes of work in Roukes's group on nanoscale electromechanical devices is pretty much "how to talk to the devices and how to listen to them," he says. To measure a system is to probe it somehow, and to probe it is to interact with it.

The problem is that interacting with the system is, in essence, to alter its properties. In the worst case, which is easy to do, one could actually heat it sufficiently to raise its energy above the point at which it would cease functioning as a quantum-limited mechanical device.

"But there are lots of different physical processes on which we can base signal transducers. We are looking for the right approach that will allow us to listen to and hear from these devices at the scale of the quantum limit," he says.

"There's lots of interesting physics, and practical applications that we are learning about in the process."

As far as the device reported in Nature is concerned, Roukes says that the scales involved set a milestone—that of submicron mechanical structures—that is encouraging for scientists and technologists in the field. In addition to possibilities for telecommunications, techniques on which the experimental prototype is based should also lead to significant improvements in magnetic resonance detection.

These, in turn, could lead to imaging with a thousand times better resolution than that currently available.

Roukes's group, in close collaboration with P. Chris Hammel's group at Los Alamos National Laboratory, is already hard at work on these possibilities.

Writer: 
Robert Tindol
Writer: 

ACE Satellite Now In Place Between Earth and Sun; Will Seek To Determine What Sun Is Made Of

PASADENA—Tanning aficionados, beach bums, surfers, and other solar enthusiasts may not realize it yet, but there is a new satellite making a huge looping halo around the sun. And it's a satellite that's going to be a benefit to weather forecasters in predicting solar flares as well as to astrophysicists in understanding the nature of the universe.

The satellite is called the Advanced Composition Explorer, or ACE for short. Launched August 25, the satellite has reached its destination about a million miles from Earth toward the sun at a position known as L1. That's the point at which the gravitational pull from Earth and sun, plus centrifugal effects, exactly balance each other.

"So, a spacecraft can orbit this invisible point, maintaining a fixed distance from Earth as Earth orbits the sun," says Ed Stone, Morrisroe Professor of Physics at Caltech and principal investigator of the ACE science mission.

Stone and Caltech physicist Dick Mewaldt are leading the satellite's science mission at the ACE Science Center at Caltech. There, they obtain spacecraft telemetry from the flight operations team at the Goddard Space Flight Center, and process the data for the astrophysics community.

The satellite is designed to collect a wide range of information on the matter it encounters. Its mission can broadly be classified in two phases:

® The satellite incorporates a real-time solar wind system that will provide around-the-clock coverage of interplanetary conditions that affect Earth. This is especially of benefit to those living at high northern and southern latitudes, because Earth's magnetic field is such that a coronal mass ejection can more easily disrupt power systems close to the poles.

While the ACE can do nothing to prevent this phenomenon from occurring, the satellite can at least provide an hour of warning that a coronal mass ejection may create a magnetic storm. The warning could help minimize and perhaps even eliminate some of the outages.

The National Oceanic and Atmospheric Administration (NOAA) will analyze the data and issue forecasts and warnings of solar storms. According to NOAA, it will be possible to issue geomagnetic storm alerts with virtually 100 percent accuracy.

® The ACE science mission is designed to measure and compare the composition of three samples of matter that can be found in interplanetary space. These are the solar material in the form of the solar wind and energetic particles accelerated by violent eruptions of the sun, the gas from the nearby space between the stars, and high-energy cosmic rays that come from more distant regions in the Milky Way.

Understanding the nature of this matter can help researchers provide answers to fundamental questions about the origin of matter. Additional information on the precise mix of elements in the solar wind, for example, will also serve as a benchmark for understanding the composition of other bodies in the solar system.

The ACE satellite is carrying nine scientific instruments that were developed by a team of scientists representing 10 institutions in the United States and Europe. These instruments are an array of mass spectrometers that measure the mass of individual ions. The satellite is already collecting data, and is expected to do so for at least five years.

"Our first look at the data tells us that the performance of the instruments is excellent," says Stone. "We should be learning what the sun is made of in the months ahead."

[Note to editors: See http://www.srl.caltech.edu/ACE/ for more on the ACE science mission. Also, NOAA on Jan. 23 issued a press release on the ACE satellite's space weather forecasting capabilities.]

Writer: 
Robert Tindol
Writer: 

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