Charles H. Townes

1915–2015

Laser pioneer Charles H. "Charlie" Townes (PhD '39), a life member of the Caltech Board of Trustees and a recipient of the 1964 Nobel Prize in Physics, died on Tuesday, January 27. He was 99 years old.

Townes, a professor of physics, emeritus, at UC Berkeley, won one-half of the Nobel Prize in Physics for his role in inventing the maser (for "microwave amplification by stimulated emission of radiation") and its cousin, the laser, in which light is emitted instead of microwaves. He shared the award with Aleksandr M. Prokhorov and Nicolai G. Basov, who independently developed the idea for a maser.

A native of Greenville, South Carolina, Townes graduated from Furman University in 1935 with a BS in physics and a BA in modern languages. He completed a master's degree in physics at Duke University in 1936 and in 1939 received his PhD in physics from Caltech. A member of the technical staff at Bell Labs through World War II, he joined the faculty at Columbia University in 1948. There, he built the first working maser. From 1959 to 1961, Townes served as vice president and director of research at the Institute for Defense Analyses in Washington, D.C.; he then served for six years as provost and professor of physics at the Massachusetts Institute of Technology.

In 1967, Townes moved to UC Berkeley, where he was named University Professor. At Berkeley, Townes transitioned into the field of infrared astronomy. Along with his colleagues, he carried out the first detection of three-atom molecules (water and ammonia) in interstellar space, and the first measurement of the mass of the black hole in the center of our galaxy. He also served as principal investigator for a pioneering program in radio and infrared astronomy, the Infrared Spatial Interferometer Array.

Townes served on many governmental panels, including the President's Science Advisory Committee from 1965 to 1969. He was the chairman of the Technical Advisory Committee for the Apollo Program until shortly after the first successful lunar landing.

Townes was named a Caltech trustee in 1979 and became a life member of the board in 1987.

In addition to the Nobel Prize, Townes was the recipient of the National Medal of Science; the National Academy of Sciences Comstock Prize and John T. Carty Medal; the Stuart Ballantine Medal of the Franklin Institute (twice); the Vannevar Bush Medal; the Lomonosov Medal of the Russian Academy of Sciences; the Niels Bohr International Gold Medal; NASA's Distinguished Public Service Medal; the Karl Schwarzschild Medal of the Astronomische Gesellschaft; and honorary degrees from 25 colleges and universities. In recognition of his lifelong interest in the intersection of science and religion, Townes was awarded the 2005 Templeton Prize. He was a member of the National Academy of Sciences, the National Academy of Engineering, the Royal Society of London, the Max Planck Society, the National Inventors Hall of Fame, and the Engineering and Science Hall of Fame.

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Caltech Professors Named Fellows of the AAAS

Caltech Professor of Astronomy George Djorgovski and chemist Bruce Brunschwig are among the 401 newly elected fellows of the American Association for the Advancement of Science (AAAS) for 2014.

The AAAS was formed in 1848 with the mission of "advancing science, engineering, and innovation throughout the world for the benefit of all people." The annual tradition of electing fellows began in 1874 to recognize scientists for their contributions toward this mission.

"The AAAS performs an essential role of promoting and protecting science and its benefits for society. This has never been more important than it is now," says Djorgovski, director of the Center for Data-Driven Discovery at Caltech. He was elected by his scientific peers to the AAAS's Section on Astronomy for his "leadership of the Virtual Observatory and the emerging field of astroinformatics, and considerable body of work on surveys and transient discovery." Astronomical data is exponentially growing in complexity and volume; the Virtual Observatory is an open, web-based research environment intended to organize, maintain, and explore the rich information content within these datasets.

"Science is being transformed by computing and information technology, and astronomy has been at the forefront of these developments," says Djorgovski.

Brunschwig, director of the Molecular Materials Research Center (MMRC) at Caltech, was elected to the AAAS's Section on Chemistry for his "pioneering contributions to the theoretical and physical understanding of electron transfer and its application to artificial photosynthesis." The MMRC is home to state-of-the-art instrumentation that facilitates cutting-edge interdisciplinary research in the fields of chemistry, surface science, and materials science. The center currently hosts myriad projects, including work on artificial photosynthesis and solar energy conversion.

"Bruce Brunschwig is a model for us to aspire to with his dedication to scholarship and his natural curiosity and inquisitiveness," says Brunschwig's colleague Nate Lewis, the George L. Argyros Professor of Chemistry at Caltech and the scientific director of the Joint Center for Artificial Photosynthesis. "His election as a fellow to the AAAS is well deserved."

Caltech is currently home to 42 fellows of the AAAS.

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SPIDER Experiment Touches Down in Antarctica

After spending 16 days suspended from a giant helium balloon floating 115,000 feet above Antarctica, a scientific instrument dubbed SPIDER has landed in a remote region of the frozen continent. Conceived of and built by an international team of scientists, the instrument launched from McMurdo Station on New Year's Day. Caltech and JPL designed, fabricated, and tested the six refracting telescopes the instrument uses to map the thermal afterglow of the Big Bang, the cosmic microwave background (CMB). SPIDER's goal: to search the CMB for the signal of inflation, an explosive event that blew our observable universe up from a volume smaller than a single atom in the first fraction of an instant after its birth.

The instrument appears to have performed well during its flight, says Jamie Bock, head of the SPIDER receiver team at Caltech and JPL. "Of course, we won't know everything until we get the full data back as part of the instrument recovery."

Read the full story and view the slideshow

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Credit: Jon Gudmundsson (Princeton University)

Each of SPIDER's six telescopes (one shown here, at left, on a lab bench) includes a pair of lenses that focus light onto a focal plane (at right) made up of 2,400 superconducting detectors. Three of the telescopes measure at a frequency of 100GHz, while the other three measure at 150GHz.

Credit: Credit: Steve Benton (University of Toronto)

Like bullets in a revolver, the six SPIDER telescopes slide into the instrument's cryostat (shown here without the telescopes). The cryostat is a large tank of liquid helium that cools SPIDER to temperatures near absolute zero so the thermal glow of the instrument itself does not overwhelm the faint signals they are trying to detect.

Credit: Steve Benton (University of Toronto)

Before SPIDER launched, many members of the team signed an out-of-the-way spot on the payload, wishing "Spidey" well and telling it to make them proud. Bill Jones, the project's principal investigator from Princeton University, also affixed a small photo of the late Andrew Lange.

Credit: Jeff Filippini

Jeff Filippini, a postdoctoral scholar who worked on the SPIDER receiver team at Caltech, stands in front of the instrument as it was being readied for launch.

Additional Caltech researchers involved in the project include professors of physics Jamie Bock and Sunil Golwala, postdoctoral scholar Lorenzo Moncelsi, and research staff members Peter Mason, Tracy Morford, and Viktor Hristov. Becky Tucker (PhD '14) and Amy Trangsrud (PhD '12) worked on the project as graduate students. The JPL team includes Marc Runyan, Anthony Turner, Krikor Megerian, Alexis Weber, Brendan Crill, Olivier Dore, and Warren Holmes.

Credit: Jeff Filippini

Prior to launch, the team laid out the parachute and hang lines in front of SPIDER, seen in the distance. The long-duration balloon that would carry SPIDER into the sky is attached to the end of the parachute shown here in the foreground.

Credit: Jeff Filippini

SPIDER and its balloon, ready for launch.

Credit: Jeff Filippini

SPIDER launched successfully on New Year's Day! Watch a video of the complete launch.

"One of the amazing things about ballooning is there is this moment where you're on the ground doing calibration work, really not in the deployment environment, and then you launch, and you start getting data back. That sharp dividing line between before and after the launch is really remarkable," says Filippini. "So many things can go wrong, and by and large, they didn't."

Credit: John Ruhl (Case Western Reserve University)

Sixteen days after launch, the team brought SPIDER back down to the ice because wind patterns suggested that the instrument might otherwise drift northward off the continent and not return to a safe recovery location. SPIDER landed in a remote area of Antarctica, more than 1,000 miles from McMurdo Station. The team is working on plans to recover the hard drives and payload.

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After spending 16 days suspended from a giant helium balloon floating 115,000 feet above Antarctica, a scientific instrument dubbed SPIDER has landed in a remote region of the frozen continent. Conceived of and built by an international team of scientists, the instrument launched from McMurdo Station on New Year's Day. Caltech and JPL designed, fabricated, and tested the six refracting telescopes the instrument uses to map the thermal afterglow of the Big Bang, the cosmic microwave background (CMB). SPIDER's goal: to search the CMB for the signal of inflation, an explosive event that blew our observable universe up from a volume smaller than a single atom in the first fraction of an instant after its birth.

The instrument appears to have performed well during its flight, says Jamie Bock, head of the SPIDER receiver team at Caltech and JPL. "Of course, we won't know everything until we get the full data back as part of the instrument recovery."

Although SPIDER relayed limited data back to the team on the ground during flight, it stored the majority of its data on hard drives, which must be recovered from the landing site. The researchers carefully monitored the experiment's flight path, and when wind patterns suggested that the winds might carry the experiment over the ocean, they opted to bring SPIDER down a bit early. It touched down in West Antarctica, more than 1,000 miles from McMurdo Station.

Jeff Filippini, a former postdoctoral scholar at Caltech and member of the SPIDER team who is now an assistant professor at the University of Illinois, Urbana-Champaign, says the landing site is near a few outlying stations. "We are negotiating plans for recovering the data disks and payload," he says. "We are all looking forward to poring over the data."

The team originally proposed SPIDER to NASA in 2005. It is an ambitious instrument, and there were many technical challenges to getting it off the ground. Political challenges also played a role: in October 2013, after the team had completed full flight preparations in the summer and transported SPIDER to the Antarctic by boat, the U.S. government shut down, canceling all Antarctic balloon flights. SPIDER had to be shipped back to the United States.

"But our team persevered," says Bock. "We used that extra time to make improvements and to fix a few problems. It is great to finally see all of our worries resolved and the hard work paying off."

A second SPIDER flight is planned for some time in the next two to three years, depending on how the hardware fares this time around.

The SPIDER project originated in the early 2000s with the late Andrew Lange's Observational Cosmology Group at Caltech and collaborators. The experiment is now led by William Jones of Princeton University, who was a graduate student of Lange's. The other primary institutions involved in the mission are the University of Toronto, Case Western Reserve University, and the University of British Columbia. SPIDER is funded by NASA, the David and Lucile Packard Foundation, the Gordon and Betty Moore Foundation, the Canadian Space Agency, and Canada's Natural Sciences and Engineering Research Council. The National Science Foundation provides logistical support to the team on the ice through the U.S. Antarctic Program.

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Fiona Harrison Awarded High-Energy Astrophysics Prize

The 2015 Rossi Prize has been awarded to Fiona Harrison, the Benjamin M. Rosen Professor of Physics at Caltech, for her "groundbreaking work on supernova remnants, neutron stars, and black holes enabled by NuSTAR." The award is the top prize in high-energy astrophysics.

Harrison is the principal investigator of NASA's NuSTAR (Nuclear Spectroscopic Telescope Array) mission. The telescope, launched in June 2012 under NASA's Small Explorer program, is the most powerful high-energy X-ray telescope ever developed. By focusing high-energy X-rays, NuSTAR is able to study some of the hottest, densest, and most energetic phenomena in the universe, including black holes, collapsed stars, and supernovae remnants. NuSTAR is conducting a census of the black holes in our cosmic neighborhood, examining the origins of high-energy particles in active galaxies, and mapping the remains of supernovae to better understand how stars explode and chemical elements are formed.

The citation for the Rossi Prize notes that Harrison's "assembly and leadership of the extraordinary NuSTAR team has opened a new window on the Universe."

"The exciting scientific results from NuSTAR are the culmination of close to two decades of work by a talented and dedicated team," says Harrison. "It is a privilege to work with them, and an honor to be recognized through the Rossi Prize."

Harrison came to Caltech as a research fellow in 1993 after earning her PhD in physics at UC Berkeley. She joined the faculty at Caltech in 1995 and was named the Benjamin M. Rosen Professor in 2013. Harrison is a member of the National Academy of Sciences and a fellow of the American Academy of Arts and Sciences and the American Physical Society. In 2013, she won a NASA Outstanding Public Leadership Medal, and she was recently elected as an Honorary Fellow of the Royal Astronomical Society.

The AAS High Energy Astrophysics Division awards the Rossi Prize annually in honor of physicist Bruno Rossi, an authority on cosmic-ray physics and a pioneer in the field of X-ray astronomy. It recognizes significant contributions to high-energy astrophysics, with particular emphasis on recent, original work. Harrison will accept the award and present a plenary lecture at the 227th annual meeting of the American Astronomical Society, which will be held in Kissimmee, Florida, in January 2016.

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Unusual Light Signal Yields Clues About Elusive Black Hole Merger

The central regions of many glittering galaxies, our own Milky Way included, harbor cores of impenetrable darkness—black holes with masses equivalent to millions, or even billions, of suns. What is more, these supermassive black holes and their host galaxies appear to develop together, or "co-evolve." Theory predicts that as galaxies collide and merge, growing ever more massive, so too do their dark hearts.

Black holes by themselves are impossible to see, but their gravity can pull in surrounding gas to form a swirling band of material called an accretion disk. The spinning particles are accelerated to tremendous speeds and release vast amounts of energy in the form of heat and powerful X-rays and gamma rays. When this process happens to a supermassive black hole, the result is a quasar—an extremely luminous object that outshines all of the stars in its host galaxy and that is visible from across the universe. "Quasars are valuable probes of the evolution of galaxies and their central black holes," says George Djorgovski, professor of astronomy and director of the Center for Data-Driven Discovery at Caltech.

In the January 7 issue of the journal Nature, Djorgovski and his collaborators report on an unusual repeating light signal from a distant quasar that they say is most likely the result of two supermassive black holes in the final phases of a merger—something that is predicted from theory but which has never been observed before. The discovery could help shed light on a long-standing conundrum in astrophysics called the "final parsec problem," which refers to the failure of theoretical models to predict what the final stages of a black hole merger look like or even how long the process might take. "The end stages of the merger of these supermassive black hole systems are very poorly understood," says the study's first author, Matthew Graham, a senior computational scientist at Caltech. "The discovery of a system that seems to be at this late stage of its evolution means we now have an observational handle on what is going on."

Djorgovski and his team discovered the unusual light signal emanating from quasar PG 1302-102 after analyzing results from the Catalina Real-Time Transient Survey (CRTS), which uses three ground telescopes in the United States and Australia to continuously monitor some 500 million celestial light sources strewn across about 80 percent of the night sky. "There has never been a data set on quasar variability that approaches this scope before," says Djorgovski, who directs the CRTS. "In the past, scientists who study the variability of quasars might only be able to follow some tens, or at most hundreds, of objects with a limited number of measurements. In this case, we looked at a quarter million quasars and were able to gather a few hundred data points for each one."

"Until now, the only known examples of supermassive black holes on their way to a merger have been separated by tens or hundreds of thousands of light years," says study coauthor Daniel Stern, a scientist at NASA's Jet Propulsion Laboratory. "At such vast distances, it would take many millions, or even billions, of years for a collision and merger to occur. In contrast, the black holes in PG 1302-102 are, at most, a few hundredths of a light year apart and could merge in about a million years or less."

Djorgovski and his team did not set out to find a black hole merger. Rather, they initially embarked on a systematic study of quasar brightness variability in the hopes of finding new clues about their physics. But after screening the data using a pattern-seeking algorithm that Graham developed, the team found 20 quasars that seemed to be emitting periodic optical signals. This was surprising, because the light curves of most quasars are chaotic—a reflection of the random nature by which material from the accretion disk spirals into a black hole. "You just don't expect to see a periodic signal from a quasar," Graham says. "When you do, it stands out."

Of the 20 periodic quasars that CRTS identified, PG 1302-102 was the best example. It had a strong, clean signal that appeared to repeat every five years or so. "It has a really nice smooth up-and-down signal, similar to a sine wave, and that just hasn't been seen before in a quasar," Graham says.

The team was cautious about jumping to conclusions. "We approached it with skepticism but excitement as well," says study coauthor Eilat Glikman, an assistant professor of physics at Middlebury College in Vermont. After all, it was possible that the periodicity the scientists were seeing was just a temporary ordered blip in an otherwise chaotic signal. To help rule out this possibility, the scientists pulled in data about the quasar from previous surveys to include in their analysis. After factoring in the historical observations (the scientists had nearly 20 years' worth of data about quasar PG 1302-102), the repeating signal was, encouragingly, still there.

The team's confidence increased further after Glikman analyzed the quasar's light spectrum. The black holes that scientists believe are powering quasars do not emit light, but the gases swirling around them in the accretion disks are traveling so quickly that they become heated into glowing plasma. "When you look at the emission lines in a spectrum from an object, what you're really seeing is information about speed—whether something is moving toward you or away from you and how fast. It's the Doppler effect," Glikman says. "With quasars, you typically have one emission line, and that line is a symmetric curve. But with this quasar, it was necessary to add a second emission line with a slightly different speed than the first one in order to fit the data. That suggests something else, such as a second black hole, is perturbing this system."

Avi Loeb, who chairs the astronomy department at Harvard University, agreed with the team's assessment that a "tight" supermassive black hole binary is the most likely explanation for the periodic signal they are seeing. "The evidence suggests that the emission originates from a very compact region around the black hole and that the speed of the emitting material in that region is at least a tenth of the speed of light," says Loeb, who did not participate in the research. "A secondary black hole would be the simplest way to induce a periodic variation in the emission from that region, because a less dense object, such as a star cluster, would be disrupted by the strong gravity of the primary black hole."

In addition to providing an unprecedented glimpse into the final stages of a black hole merger, the discovery is also a testament to the power of "big data" science, where the challenge lies not only in collecting high-quality information but also devising ways to mine it for useful information. "We're basically moving from having a few pictures of the whole sky or repeated observations of tiny patches of the sky to having a movie of the entire sky all the time," says Sterl Phinney, a professor of theoretical physics at Caltech, who was also not involved in the study. "Many of the objects in the movie will not be doing anything very exciting, but there will also be a lot of interesting ones that we missed before."

It is still unclear what physical mechanism is responsible for the quasar's repeating light signal. One possibility, Graham says, is that the quasar is funneling material from its accretion disk into luminous twin plasma jets that are rotating like beams from a lighthouse. "If the glowing jets are sweeping around in a regular fashion, then we would only see them when they're pointed directly at us. The end result is a regularly repeating signal," Graham says.

Another possibility is that the accretion disk that encircles both black holes is distorted. "If one region is thicker than the rest, then as the warped section travels around the accretion disk, it could be blocking light from the quasar at regular intervals. This would explain the periodicity of the signal that we're seeing," Graham says. Yet another possibility is that something is happening to the accretion disk that is causing it to dump material onto the black holes in a regular fashion, resulting in periodic bursts of energy.

"Even though there are a number of viable physical mechanisms behind the periodicity we're seeing—either the precessing jet, warped accretion disk or periodic dumping—these are all still fundamentally caused by a close binary system," Graham says.

Along with Djorgovski, Graham, Stern, and Glikman, additional authors on the paper, "A possible close supermassive black hole binary in a quasar with optical periodicity," include Andrew Drake, a computational scientist and co-principal investigator of the CRTS sky survey at Caltech; Ashish Mahabal, a staff scientist in computational astronomy at Caltech; Ciro Donalek, a computational staff scientist at Caltech; Steve Larson, a senior staff scientist at the University of Arizona; and Eric Christensen, an associate staff scientist at the University of Arizona. Funding for the study was provided by the National Science Foundation.

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