Caltech-Led Astronomers Discover Galaxies Near Cosmic Dawn

Researchers conduct first census of the most primitive and distant galaxies seen

PASADENA, Calif.—A team of astronomers led by the California Institute of Technology (Caltech) has used NASA's Hubble Space Telescope to discover seven of the most primitive and distant galaxies ever seen.

One of the galaxies, the astronomers say, might be the all-time record holder—the galaxy as observed existed when the universe was merely 380 million years old. All of the newly discovered galaxies formed more than 13 billion years ago, when the universe was just about 4 percent of its present age, a period astronomers call the "cosmic dawn," when the first galaxies were born. The universe is now 13.7 billion years old.

The new observations span a period between 350 million and 600 million years after the Big Bang and represent the first reliable census of galaxies at such an early time in cosmic history, the team says. The astronomers found that the number of galaxies steadily increased as time went on, supporting the idea that the first galaxies didn't form in a sudden burst but gradually assembled their stars.

Because it takes light billions of years to travel such vast distances, astronomical images show how the universe looked during the period, billions of years ago, when that light first embarked on its journey. The farther away astronomers peer into space, the further back in time they are looking.

In the new study, which was recently accepted for publication in the Astrophysical Journal Letters, the team has explored the deepest reaches of the cosmos—and therefore the most distant past—that has ever been studied with Hubble.

"We've made the longest exposure that Hubble has ever taken, capturing some of the faintest and most distant galaxies," says Richard Ellis, the Steele Family Professor of Astronomy at Caltech and the first author of the paper. "The added depth and our carefully designed observing strategy have been the key features of our campaign to reliably probe this early period of cosmic history."

The results are the first from a new Hubble survey that focused on a small patch of sky known as the Hubble Ultra Deep Field (HUDF), which was first studied nine years ago. The astronomers used Hubble's Wide Field Camera 3 (WFC3) to observe the HUDF in near-infrared light over a period of six weeks during August and September 2012.

To determine the distances to these galaxies, the team measured their colors using four filters that allow Hubble to capture near-infrared light at specific wavelengths. "We employed a filter that has not been used in deep imaging before, and undertook much deeper exposures in some filters than in earlier work, in order to convincingly reject the possibility that some of our galaxies might be foreground objects," says team member James Dunlop of the Institute for Astronomy at the University of Edinburgh.

The carefully chosen filters allowed the astronomers to measure the light that was absorbed by neutral hydrogen, which filled the universe beginning about 400,000 years after the Big Bang. Stars and galaxies started to form roughly 200 million years after the Big Bang. As they did, they bathed the cosmos with ultraviolet light, which ionized the neutral hydrogen by stripping an electron from each hydrogen atom. This so-called "epoch of reionization" lasted until the universe was about a billion years old.

If everything in the universe were stationary, astronomers would see that only a specific wavelength of light was absorbed by neutral hydrogen. But the universe is expanding, and this stretches the wavelengths of light coming from galaxies. The amount that the light is stretched—called the redshift—depends on distance: the farther away a galaxy is, the greater the redshift.

As a result of this cosmic expansion, astronomers observe that the absorption of light by neutral hydrogen occurs at longer wavelengths for more distant galaxies. The filters enabled the researchers to determine at which wavelength the light was absorbed; this revealed the distance to the galaxy—and therefore the period in cosmic history when it is being formed. Using this technique to penetrate further and further back in time, the team found a steadily decreasing number of galaxies.

"Our data confirms that reionization is a drawn-out process occurring over several hundred million years with galaxies slowly building up their stars and chemical elements," says coauthor Brant Robertson of the University of Arizona in Tucson. "There wasn't a single dramatic moment when galaxies formed; it's a gradual process."

The new observations—which pushed Hubble to its technical limits—hint at what is to come with next-generation infrared space telescopes, the researchers say. To probe even further back in time to see ever more primitive galaxies, astronomers will need to observe in wavelengths longer than those that can be detected by Hubble. That's because cosmic expansion has stretched the light from the most distant galaxies so much that they glow predominantly in the infrared. The upcoming James Webb Space Telescope, slated for launch in a few years, will target those galaxies.

"Although we may have reached back as far as Hubble will see, Hubble has, in a sense, set the stage for Webb," says team member Anton Koekemoer of the Space Telescope Science Institute in Baltimore. "Our work indicates there is a rich field of even earlier galaxies that Webb will be able to study."

The title of the Astrophysical Journal Letters paper is, "The Abundance of Star-Forming Galaxies in the Redshift Range 8.5 to 12: New Results from the 2012 Hubble Ultra Deep Field Campaign." In addition to Ellis, Dunlop, Robertson, and Koekemoer, the other authors on the Astrophysical Journal Letters paper are Matthew Schenker of Caltech; Ross McLure, Rebecca Bowler, Alexander Rogers, Emma Curtis-Lake, and Michele Cirasuolo of the Institute for Astronomy at the University of Edinburgh; Yoshiaki Ono and Masami Ouchi of the University of Tokyo; Evan Schneider of the University of Arizona; Daniel Stark of the University of Cambridge; Stéphane Charlot of the Institut d'Astrophysique de Paris; and Steven Furlanetto of UCLA. The research was supported by the Space Telescope Science Institute, the European Research Council, the Royal Society, and the Leverhulme Trust.

Science Contacts:

Richard Ellis, Steele Professor of Astronomy
(626) 676-5530

Matt Schenker, graduate student
(516) 428-0587

Marcus Woo
Exclude from News Hub: 
News Type: 
Research News

Top 12 in 2012

Frontpage Title: 
Top 12 in 2012
Credit: Benjamin Deverman/Caltech

Gene therapy for boosting nerve-cell repair

Caltech scientists have developed a gene therapy that helps the brain replace its nerve-cell-protecting myelin sheaths—and the cells that produce those sheaths—when they are destroyed by diseases like multiple sclerosis and by spinal-cord injuries. Myelin ensures that nerve cells can send signals quickly and efficiently.

Credit: L. Moser and P. M. Bellan, Caltech

Understanding solar flares

By studying jets of plasma in the lab, Caltech researchers discovered a surprising phenomenon that may be important for understanding how solar flares occur and for developing nuclear fusion as an energy source. Solar flares are bursts of energy from the sun that launch chunks of plasma that can damage orbiting satellites and cause the northern and southern lights on Earth.

Coincidence—or physics?

Caltech planetary scientists provided a new explanation for why the "man in the moon" faces Earth. Their research indicates that the "man"—an illusion caused by dark-colored volcanic plains—faces us because of the rate at which the moon's spin rate slowed before becoming locked in its current orientation, even though the odds favored the moon's other, more mountainous side.

Choking when the stakes are high

In studying brain activity and behavior, Caltech biologists and social scientists learned that the more someone is afraid of loss, the worse they will perform on a given task—and that, the more loss-averse they are, the more likely it is that their performance will peak at a level far below their actual capacity.

Credit: NASA/JPL-Caltech

Eyeing the X-ray universe

NASA's NuSTAR telescope, a Caltech-led and -designed mission to explore the high-energy X-ray universe and to uncover the secrets of black holes, of remnants of dead stars, of energetic cosmic explosions, and even of the sun, was launched on June 13. The instrument is the most powerful high-energy X-ray telescope ever developed and will produce images that are 10 times sharper than any that have been taken before at these energies.

Credit: CERN

Uncovering the Higgs Boson

This summer's likely discovery of the long-sought and highly elusive Higgs boson, the fundamental particle that is thought to endow elementary particles with mass, was made possible in part by contributions from a large contingent of Caltech researchers. They have worked on this problem with colleagues around the globe for decades, building experiments, designing detectors to measure particles ever more precisely, and inventing communication systems and data storage and transfer networks to share information among thousands of physicists worldwide.

Credit: Peter Day

Amplifying research

Researchers at Caltech and NASA's Jet Propulsion Laboratory developed a new kind of amplifier that can be used for everything from exploring the cosmos to examining the quantum world. This new device operates at a frequency range more than 10 times wider than that of other similar kinds of devices, can amplify strong signals without distortion, and introduces the lowest amount of unavoidable noise.

Swims like a jellyfish

Caltech bioengineers partnered with researchers at Harvard University to build a freely moving artificial jellyfish from scratch. The researchers fashioned the jellyfish from silicon and muscle cells into what they've dubbed Medusoid; in the lab, the scientists were able to replicate some of the jellyfish's key mechanical functions, such as swimming and creating feeding currents. The work will help improve researchers' understanding of tissues and how they work, and may inform future efforts in tissue engineering and the design of pumps for the human heart.

Credit: NASA/JPL-Caltech

Touchdown confirmed

After more than eight years of planning, about 354 million miles of space travel, and seven minutes of terror, NASA's Mars Science Laboratory successfully landed on the Red Planet on August 5. The roving analytical laboratory, named Curiosity, is now using its 10 scientific instruments and 17 cameras to search Mars for environments that either were once—or are now—habitable.

Credit: Caltech/Michael Hoffmann

Powering toilets for the developing world

Caltech engineers built a solar-powered toilet that can safely dispose of human waste for just five cents per use per day. The toilet design, which won the Bill and Melinda Gates Foundation's Reinventing the Toilet Challenge, uses the sun to power a reactor that breaks down water and human waste into fertilizer and hydrogen. The hydrogen can be stored as energy in hydrogen fuel cells.

Credit: Caltech / Scott Kelberg and Michael Roukes

Weighing molecules

A Caltech-led team of physicists created the first-ever mechanical device that can measure the mass of an individual molecule. The tool could eventually help doctors to diagnose diseases, and will enable scientists to study viruses, examine the molecular machinery of cells, and better measure nanoparticles and air pollution.

Splitting water

This year, two separate Caltech research groups made key advances in the quest to extract hydrogen from water for energy use. In June, a team of chemical engineers devised a nontoxic, noncorrosive way to split water molecules at relatively low temperatures; this method may prove useful in the application of waste heat to hydrogen production. Then, in September, a group of Caltech chemists identified the mechanism by which some water-splitting catalysts work; their findings should light the way toward the development of cheaper and better catalysts.


In 2012, Caltech faculty and students pursued research into just about every aspect of our world and beyond—from understanding human behavior, to exploring other planets, to developing sustainable waste solutions for the developing world.

In other words, 2012 was another year of discovery at Caltech. Here are a dozen research stories, which were among the most widely read and shared articles from

Did we skip your favorite? Connect with Caltech on Facebook to share your pick.

Exclude from News Hub: 
bbell2's picture

H. Jeff Kimble to Receive Quantum Physics Award

The German Physical Society (Deutsche Physikalische Gesellschaft, or DPG) and the Optical Society of America (OSA) have selected Caltech physics professor H. Jeff Kimble to receive the Herbert Walther Award for his "pioneering experimental contributions to quantum optics, cavity quantum electrodynamics, and quantum information science."

"It is a special honor for me to receive this award since I have the greatest respect for Professor Walther, beginning when we first met when I was a graduate student and continuing over almost 30 years as scientific colleagues and competitors," says Kimble, William L. Valentine Professor and professor of physics at Caltech. "Walther made historic contributions to physics that have shaped the future that we now all enjoy."

The Herbert Walther Award highlights scientific contributions in quantum optics and atomic physics and recognizes individuals for their efforts to promote excellence in the international scientific community. Kimble will accept the award at the Laser World of Photonics Conference in Munich, Germany, in May 2013.

Kimble became a professor of physics at Caltech in 1989. He was named Valentine Professor in 1997 and director of the Institute for Quantum Information and Matter at Caltech in 2011. He has cemented his reputation in quantum optics through discoveries relating to quantum measurement and quantum information science.

Kimble's research has led to greater understanding of novel quantum states of the electromagnetic field, such as "squeezed" and "antibunched" light. His demonstration in 1995 of a quantum phase gate that operated at the single photon level and was suitable for the implementation of rudimentary quantum logic has been considered seminal in establishing the experimental foundations of quantum information science. Kimble and his colleagues have also made important contributions to theoretical physics, including a new paradigm for the realization of distributed quantum networks.

The Herbert Walther Award was first given by the DPG and OSA in 2007. The namesake of the award, Herbert Walther, was a well-known scientist and educator from the Max Planck Institute for Quantum Optics (of which he was founding director) and Ludwig Maximilians University, Munich, who made significant contributions to the field of laser physics and optics; he passed away in 2006. Past recipients of the award include Alain Aspect, Marlan O. Scully, Serge Haroche, and David J. Wineland.

Brian Bell
Home Page Title: 
Kimble to Receive Physics Award
Listing Title: 
Kimble to Receive Physics Award
Exclude from News Hub: 

The Miracle and Beauty of Physics: An Interview with Cliff Cheung

When you lift a paper clip off a table with a small magnet, you're accomplishing a remarkable feat: the tiny magnet is overcoming the gravitational pull from the entire Earth. Why does gravity seem so weak compared to electromagnetism and the other fundamental forces of nature? This vast discrepancy in scale—how a small magnet can beat out a whole planet—is related to what physicists call the hierarchy problem.

Cliff Cheung—who joined Caltech this fall as an assistant professor of theoretical physics—is fascinated by this "very deep puzzle" (which may be solved through supersymmetry, a class of theories in which every fundamental particle has a partner particle, as well as by dark matter, the mysterious stuff that accounts for nearly a quarter of the universe). Recently, Cheung—who also plays guitar and piano, sings, and writes music—answered a few questions about coming to Caltech and his passion for physics.

What are you looking forward to about Caltech?

The environment here is fantastic. Caltech puts a lot of firepower behind a very small number of people. It's like having an academic steamroller on your side, so to speak. In my case, Caltech has been incredibly generous and supportive in all respects so far.

I'm super excited to be joining the theory group in particular, which is a powerhouse in a range of topics, including particle physics, cosmology, and string theory. Personally, it's surreal and humbling to be here given Caltech's legendary physics legacy.

Why do you think physics is exciting?

It works. When I was a student seeing the Standard Model [the theory of how all fundamental particles behave and interact] for the first time, I remembering thinking, this theory is very strange and very alien. But then you actually start calculating and you see what it predicts—and it works! There's a certain miracle in being able to write down something on a piece of paper which explains almost every experiment on record. That miracle is what excites a lot of us.

When someone writes down a formula or a theory, any physicist worth his salt can judge: is this beautiful or is this ugly? Equations that describe the universe can have a certain kind of elegance or they may not. In this sense, the ideas that we discuss have an intrinsic beauty.

That sense of beauty seems to emphasize the point that science, and physics in particular, is a very human endeavor.

That's right. It's much less cold than you think. This isn't meant to detract from what we do, but there is a certain subjectivity that I think is a very good thing. The fact that there are experiments to keep us honest is essential—at least for a particle physicist like myself. But at the same time we can enjoy the beauty of the models we write down

How did you become interested in physics?

I've had a couple of formative experiences. When I was in high school there was this wonderful program at Columbia University where you took a test and if you passed they let you take a class on the weekends. It's what nerds do. Anyway, I remember taking this class on special relativity, which to a high-school student is eye opening, but not so foreign as to be disconcerting. Special relativity is really just mechanics, but with a twist. Seeing these ideas for the first time made me think, I want to do this

This experience connected with me because I felt like I could really see the history as I learned the physics. I imagined Einstein in a room, writing down the equations for his gedanken [thought] experiments and I realized that just by thinking, it was possible to determine tangible and deep facts about the world around us. That's a pretty powerful thing. Learning that this was possible—that you could come up with the rules without actually playing the game—was absolutely amazing to me. You just had to use your brain. 

Born in Cleveland, Cheung grew up in the suburbs of New York City. He went on to Yale, where he received his BS in 2004. He finished his PhD from Harvard in 2009, before spending the past few years at UC Berkeley and Lawrence Berkeley National Laboratory as a postdoc.

Marcus Woo
Exclude from News Hub: 
News Type: 
Research News

A Sky Full of Planets

Think back to the last time you saw the Milky Way—that faint stripe of stars that thickens and brightens as you get farther from city lights. At least 200 billion stars fill the Milky Way, our galaxy. How many planets might orbit those stars? What would those worlds be like? Twenty years ago, it was anybody's guess.  

In the 1990s, astronomers began to discover planets around other stars—so-called exoplanets. Since then, the confirmed count of exoplanets has skyrocketed to more than 850, with thousands of candidates awaiting follow-up. Astronomers now estimate that the stars in our Milky Way have an average of at least one planet each. (The next time you look up into the night sky, think about that.)

The sudden prospect of characterizing so many solar systems in our own galaxy has brought together two once-isolated camps: planetary scientists, who generally focus on the inside of our solar system, and astronomers, who mostly look beyond it. Planetary scientists see an opportunity to learn about our solar system and its origins by putting it into the context of a huge ensemble of other solar systems, and astronomers have a keen interest in what planetary scientists might help them discover about planet formation on a galactic or even larger scale.

To those ends, nine Caltech astronomers and planetary scientists are forming a Center for Planetary Astronomy. Joining together in a single research center will help them maintain fruitful collaborations, collectively attract research funding and fellowships for young scholars, and recruit top students and postdoctoral scholars.

The nascent center's members bring complementary perspectives to the characterization of our newly discovered neighbors. Planetary science professor Geoff Blake, astronomy professor Lynn Hillenbrand, and senior research associate John Carpenter study planet-forming disks of gas and dust around young stars. Mike Brown, the Richard and Barbara Rosenberg Professor and professor of planetary astronomy, and Caltech's infamous Pluto-killer, studies fossil rubble from just such a disk—a fantastic array of thousands of planetesimals and chunks of rock and ice on the fringes of our solar system, known as the Kuiper belt, that yields clues to the primordial solar system. The remaining scientists are focused more on the planets themselves. John Johnson, an assistant professor of planetary astronomy, focuses on the detection and characterization of exoplanets, searches for worlds like Earth, and investigates how stars' masses affect planet formation by studying the relationships between exoplanets and the very different types of stars that they orbit. Heather Knutson, an assistant professor of planetary science, characterizes exoplanets' compositions, temperatures, atmospheres, and even their weather. Yuk Yung, the Smits Family Professor of Planetary Science, studies the atmospheres of planets, and Dave Stevenson, the Marvin L. Goldberger Professor of Planetary Science, studies planetary interiors and how they evolve. Gregg Hallinan, an assistant professor of astronomy, is trying to detect radio signals from exoplanets, which would indicate the presence of magnetic fields that could be a signature of habitability.

The center's members are excited about its potential contribution to the major discoveries that are sure to come in this field. "The unique combination of Caltech's top-ranked astronomical facilities, astronomy program, and planetary science program will allow us to access the deep and broad knowledge about planets and planetary systems that only comes from such a joint endeavor," says Brown.

Says Knutson, "I was trained as an astronomer, but what I do is planetary science. Caltech is one of the few places where we have great conversations between the two groups. And Caltech's resources, in terms of telescopes, give us the opportunity to move quickly and think big." 

Exclude from News Hub: 
News Type: 
Research News

High-Energy Physicists Smash Records for Network Data Transfer

New methods for efficient use of long-range networks will support cutting-edge science

PASADENA, Calif.—Physicists led by the California Institute of Technology (Caltech) have smashed yet another series of records for data-transfer speed. The international team of high-energy physicists, computer scientists, and network engineers reached a transfer rate of 339 gigabits per second (Gbps)—equivalent to moving four million gigabytes (or one million full length movies) per day, nearly doubling last year's record. The team also reached a new record for a two-way transfer on a single link by sending data at 187 Gbps between Victoria, Canada, and Salt Lake City.

The achievements, the researchers say, pave the way for the next level of data-intensive science—in fields such as high-energy physics, astrophysics, genomics, meteorology, and global climate tracking. For example, last summer's discovery at the Large Hadron Collider (LHC) in Geneva of a new particle that may be the long-sought Higgs boson was made possible by a global network of computational and data-storage facilities that transferred more than 100 petabytes (100 million gigabytes) of data in the past year alone. As the LHC continues to slam protons together at higher rates and with more energy, the experiments will produce an even larger flood of data—reaching the exabyte range (a billion gigabytes).

The researchers, led by Caltech, the University of Victoria, and the University of Michigan, together with Brookhaven National Lab, Vanderbilt University, and other partners, demonstrated their achievement at the SuperComputing 2012 (SC12) conference, November 12–16 in Salt Lake City. They used wide-area network circuits connecting Caltech, the University of Victoria Computing Center in British Columbia, the University of Michigan, and the Salt Palace Convention Center in Utah. While setting the records, they also demonstrated other state-of-the-art methods such as software-defined intercontinental networks and direct interconnections between computer memories over the network between Pasadena and Salt Lake City.

"By sharing our methods and tools with scientists in many fields, we aim to further enable the next round of scientific discoveries, taking full advantage of 100-Gbps networks now, and higher-speed networks in the near future," says Harvey Newman, professor of physics at Caltech and the leader of the team. "In particular, we hope that these developments will afford physicists and students throughout the world the opportunity to participate directly in the LHC's next round of discoveries as they emerge."

As the demand for "Big Data" continues to grow exponentially—both in major science projects and in the world at large—the team says they look forward to next year's round of tests using network and data-storage technologies that are just beginning to emerge. Armed with these new technologies and methods, the Caltech team estimates that they may reach 1 terabit-per-second (a thousand gbps) data transfers over long-range networks by next fall. 

More information about the demonstration can be found at

Exclude from News Hub: 
News Type: 
Research News
Tuesday, April 9, 2013
Avery Library – Avery House

Spring Teaching Assistant Orientation

Caltech Faculty Named AMS Fellows

Nine members of Caltech's faculty have been named to the inaugural class of Fellows of the American Mathematical Society (AMS). According to the AMS, the distinction recognizes members of the society "who have made outstanding contributions to the creation, exposition, advancement, communication, and utilization of mathematics." There are 1,119 Fellows in the inaugural class from more than 600 institutions.

Caltech's Fellows are

Tom Apostol, Professor of Mathematics, Emeritus

Michael Aschbacher, Shaler Arthur Hanisch Professor of Mathematics

Danny Calegari, Richard Merkin Distinguished Professor of Mathematics

Yizhao Thomas Hou, Charles Lee Powell Professor of Applied and Computational Mathematics

Alexander Kechris, Professor of Mathematics

Wilhelmus Luxemburg, Professor of Mathematics, Emeritus

Hirosi Ooguri, Fred Kavli Professor of Theoretical Physics and Mathematics

Dinakar Ramakrishnan, Taussky-Todd-Lonergan Professor of Mathematics

Barry Simon, International Business Machines Professor of Mathematics and Theoretical Physics

"I'm delighted that the American Mathematical Society has recognized so many of our mathematics faculty for inclusion in their first class of Fellows," says Tom Soifer, chair of the Division of Physics, Mathematics and Astronomy. "This is a clear recognition of the quality and stature of our mathematics faculty by the world's largest and most influential society for mathematical research and education."

Marcus Woo
Exclude from News Hub: 
News Type: 
In Our Community

Caltech Mourns the Passing of Wallace L. W. Sargent


Wallace "Wal" Sargent passed away on October 29 at the age of 77. He was the Ira S. Bowen Professor of Astronomy, Emeritus, at Caltech. He was an outstanding observational astronomer at the forefront of spectroscopy for over 50 years during an immensely productive and distinguished career. He began his career at the Institute as a research fellow in Astronomy from 1959 to 1962. He returned as an assistant professor in 1966, becoming full professor in 1971 and Bowen Professor in 1981. Sargent served as Caltech's executive officer of astronomy from 1975 to 1981 and again from 1996 to 1997 and as the director of Palomar Observatory from 1997 to 2000.

Sargent was born in 1935 in Elsham, United Kingdom, and he was the first pupil of the Scunthorpe Technical High School to go to a university. He entered the University of Manchester in 1953, where he earned his bachelor's, master's, and PhD degrees, as well as becoming a lifelong supporter of Manchester United. It was shortly after graduation that Sargent came to Caltech as a research fellow. From 1962 to 1964 he was a senior research fellow at the Royal Greenwich Observatory, where he met and married astronomer Anneila Sargent (née Cassells), now the Benjamin M. Rosen Professor of Astronomy at Caltech and the vice president for student affairs.

Perhaps the most remarkable aspect of Sargent's contributions to astrophysics is the range of subjects in which he made fundamental advances. Among his accomplishments were the demonstration that most of the helium in the universe was produced in the Big Bang with which the universe began (with Leonard Searle), the first dynamical evidence for the presence of supermassive black holes at the centers of galaxies (with his student Peter Young), the measurement of the mass of the Milky Way Galaxy using the radial velocities of outer satellites, the discovery that most nearby galaxies harbor low-luminosity nuclear activity, and illuminating studies on the emission from quasars and Seyfert galaxies.

As varied as Sargent's scientific accomplishments have been, there is one area of astrophysics where he both pioneered the field and has remained in the forefront to this day: the astrophysics of the diffuse intergalactic medium and the chemical history of the universe. This field gave us the first glimpses of the high-redshift universe at a time when normal galaxies could only be seen to small cosmological distances.

Sargent is considered the father of quasar absorption line spectroscopy. Using innovative new astronomical detectors developed by his collaborator, Alec Boksenberg, Sargent explored the gas permeating the high-redshift universe. Sargent had the foresight to recognize the advantages for faint-object spectroscopy of a new kind of  electronic detector, the Image Photon Counting System, developed by Boksenberg at University College London. The Sargent-Boksenberg partnership—"Boksenberg's Flying Circus" as Sargent affectionately dubbed it—revolutionized the field by carrying out the first statistically rigorous surveys of  quasar absorption systems. Sargent, with Boksenberg and their collaborators, gave us a key physical insight into the nature of the material between galaxies and brought to the fore the importance of this technique for observational cosmology. They used this information to understand how the material of which we are made has evolved since the first galaxies formed.

Sargent led the second Palomar Observatory Sky Survey, a photographic survey of the entire northern sky that was converted to a digital image format so that it could be analyzed via computers. This process produced a catalog of over 50 million galaxies and half a billion stars, including tens of thousands of quasars, and was a model for the many surveys that have followed using CCDs.

Sargent was a leader in the development of the W. M. Keck Observatory, coleading its science steering committee during the observatory's crucial formative years. With the advent of the Keck telescopes, he capitalized on the new powerful instruments on the world's largest telescopes to extend his research to probe the material between galaxies to the farthest reaches of the universe. Sargent established the existence of metals, the products of stellar nucleosynthesis, in the intergalactic medium only a billion years or so after the Big Bang. This research is helping us to identify and understand the first stars to form in the infant universe, which will be the targets of the next generation of telescopes.

In addition to his research, Sargent had a major influence on astronomy as an educator, particularly through the string of brilliant, accomplished graduate students that he mentored during his career.

Chuck Steidel (PhD '90), the Lee A. DuBridge Professor of Astronomy at Caltech, was a graduate student of Sargent's in the late 1980s and remembers his ability to inject humor into any situation that was in danger of becoming overly serious. "This was quite necessary for calming a young graduate student such as myself," admits Steidel. "Our conversations would almost always end up on a topic other than my thesis—baseball, music, literature, sumo wrestling. Looking back it is hard to recall ever receiving direct advice from Wal, and yet somehow he profoundly influenced the way I view science. As a colleague, Wal has been just as important to me," continues Steidel. "Wal will be missed for much more than his scientific accomplishments."

Alex Filippenko (PhD '84), a professor of astronomy at the University of California, Berkeley, was also mentored by Sargent during his graduate studies at Caltech. At the end of a five-night observing run at Palomar Observatory in 1985 they made a chance discovery of a new type of supernova, and although Sargent had studied supernovae many years earlier, Filippenko recalls that Sargent gave him the lead in the analysis and publication of their results. "This literally changed my career," Filippenko says. "Wal always encouraged his students to capitalize on exciting opportunities that came their way."

Sargent has received many honors—he was named a fellow of the American Academy of Arts and Sciences in 1977, a fellow of the Royal Society in 1981, and a member of the National Academy of Sciences in 2005. He was awarded the Helen B. Warner Prize of the American Astronomical Society in 1969, gave the George Darwin Lecture of the Royal Astronomical Society in 1987, received the Dannie Heineman Prize of the American Astronomical Society and the American Institute of Physics in 1991, received the Catherine Wolfe Bruce Medal of the Astronomical Society of the Pacific in 1994, and was the Henry Norris Russell Lecturer of the American Astronomical Society in 2001. Sargent was a member of more than 30 review and prize committees over the span of his career and a visiting fellow at observatories around the world, from Australia to Europe to Berkeley, California.

Sargent is survived by his wife, Anneila Sargent; two daughters, Lindsay Eleanor Berg and Alison Clare Hubbs; sons-in-law Henry Berg and Dan Hubbs; and four grandsons—Patrick and Charlie Hubbs and Angus and Eric Berg. A public memorial reception will be held at a later date.

Donations can be made in memory of Wallace L. W. Sargent here.


Exclude from News Hub: 
News Type: 
In Our Community

Two Faculty Members Named Packard Fellows

Two Caltech faculty members have been awarded Packard Fellowships for Science and Engineering. Biologist Alexei Aravin and astronomer John Johnson each were awarded $875,000, to be distributed over five years.

"I'm very excited about this fellowship," says Aravin, an assistant professor of biology. "It will allow my lab to pursue new, ambitious goals that are difficult to fund using traditional sources."

Aravin studies RNA molecules, which encode the information contained in genes to help create proteins. His lab is probing the mechanisms that determine the stability and fate of RNA. He's also trying to figure out how noncoding RNA—which doesn't encode information but nevertheless plays crucial roles in the cell—functions and is produced.

Johnson's research focuses on discovering and characterizing planets around other stars. "My broad goals," he says, "are to gain a better understanding of planet formation, place our solar system in a broader galactic context, and eventually find places in the galaxy where other life forms might reside." He plans to use the money to help support postdocs in his research group and to start a visitor program in which scientists from other institutions are invited to brainstorm and collaborate.

Johnson, an assistant professor of astronomy, was meeting with a student when he got the phone call notifying him of the award. "I don't remember my exact reaction, but it certainly startled the poor student," he says. "I spent the rest of the day grinning like an idiot."

According to the Packard Foundation, the fellowships were established in 1988 to allow promising professors to pursue research early in their careers with few funding and reporting constraints. Each year, presidents from 50 universities each nominate two early-career professors for the fellowship. A panel of scientists and engineers then select 16 fellows. To date, there have been more than 400 professors who have received Packard Fellowships. Aravin and Johnson join 26 members of current and past Caltech faculty who have been named Packard Fellows.

Marcus Woo
Home Page Title: 
New Caltech Fellows
Exclude from News Hub: 
News Type: 
In Our Community