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Fifty Years of Quasars

A Milestone for Astronomy

Radio astronomy was booming in the 1950s. After World War II, a slew of slightly used 7.5-meter-diameter antiaircraft radar antennas (called Würzburg dishes, so you can guess where they came from) were suddenly available for civilian use. Larger, purpose-built dishes also had sprung up in England, Australia, and North America. The so-called Third Cambridge catalog (3C for short), published in 1959 by a consortium of British radio astronomers, listed several hundred bright radio sources in the northern-hemisphere sky.

In those days, a radio telescope recorded a wavy line on a roll of chart paper. In order to figure out what the source was, you had to train an optical telescope on the same point in the sky. But as seen through a really large telescope, such as Caltech's 200-inch Hale Telescope atop Palomar Mountain, the sky is a very crowded place. Picking out the radio source from the myriad of small blots on a photographic plate requires extremely accurate coordinates.

Up at Caltech's Owens Valley Radio Observatory, sandwiched between the Sierra and Inyo National Forests and some five hours' drive north of civilization (or at least Pasadena), Thomas Matthews was using a pair of brand-new, 90-foot-diameter dishes to calculate such coordinates accurately enough for the Hale. He would map these onto photo prints from Palomar's 48-inch survey telescope and pass them on to a young astronomy professor named Maarten Schmidt, who would take the spectrum of that particular blot.

Every chemical element, when sufficiently heated, emits visible light at a few specific, well-known wavelengths. (Imagine a picket fence painted in all the hues of a rainbow from red to blue, but with most of the boards missing.) This spectral "fingerprint" is revealed when the light is separated into its constituent colors by an instrument called a spectrometer. The more distant a galaxy is, the more its light gets stretched, en route to us, by the relentless expansion of the universe. Measuring how much a given line has been shifted toward redder, longer wavelengths tells you how long the light's been traveling and thus how far it has come.

Most of the 3C radio sources were elliptical galaxies—featureless blobs lying at distances up to about three billion light-years away. But every now and then the source would be a starlike pinprick of light. True divas, these "stars" had spectra that could not be deciphered. Worse, they couldn't even be matched to one another. Each one was different; unique.

One such "star" was 3C 273, one of the brightest radio sources in the 3C catalog—and it lies only two degrees north of the celestial equator, which means it's visible from much of Earth's southern hemisphere as well. And this is a very good thing, because in 1962, Australian radio astronomers Cyril Hazard, M. B. Mackey, and Albert Shimmins aimed the 210-foot Parkes radio telescope, some 200 miles west of Sydney, at 3C 273 on three occasions when the moon passed in front of it. Matthews was using interferometry, triangulating the source's position from the very slight difference in the arrival times of its wave peaks at his two radio dishes. By noting the exact instant that 3C 273 winked out or reemerged, the Aussies nailed its position far more accurately. They also discovered that 3C 273 was really two radio sources very close together. They passed their findings on to Matthews, who worked them up and gave them to Schmidt, and when Schmidt went to Palomar in late December 1962, 3C 273 was on his to-do list.

The spectrograph Schmidt was using was mounted in the Hale's prime focus cage—a barrel six feet in diameter built into the telescope's steel skeleton some 50 feet above the mirror. The cage is accessible by an elevator that is moved out of the way during observations; anyone in the cage is marooned for the duration.

Schmidt had to be up there to keep the pinpoint of light he was seeking visually lined up on the spectrograph's slit, using a set of push buttons at his fingertips to control the stately motion of the telescope. "It was romantic!" he recalls fondly. "Once in a while you just had to stop and look around you. At times it could be damned cold, but I had a hot suit"—a pair of electrically heated coveralls also apparently left over from World War II. "It said 'Army Air Forces' on the front, and it did a rather good job of keeping you warm."

Schmidt's workday began in the darkroom, where he prepared his plates for the night. Each one was a thin sheet of glass, about an inch long and a third of an inch wide, cut down from the standard five-by-seven-inch plates used for full-field photographic work, and mounted in a plate holder. The holders, in turn, were packed in a light-tight box about the size of a cigar box for their journey to and from the spectrograph. As sensitive as they were, the plates were only about 2 percent efficient, Schmidt recalls, "which means that 98 percent of the light essentially wasn't used. Therefore the observations were very slow. I spent my night, typically, on one object that I observed for seven or eight hours, and then a brighter object that I might observe for one or two hours. And that was the whole night—two plates. Two objects. Slow work."

3C 273's two radio sources proved to be a relatively bright star and a very faint jet of gaseous material. And by "relatively bright," Schmidt means "dim." Since ancient times, astronomers have ranked stars by their magnitude, with first magnitude being the brightest: Sirius, Arcturus, Vega, Antares, and the like. The faintest stars visible to the naked eye are sixth magnitude. This star was magnitude 13, but it far outshone the radio galaxies he was used to photographing. "The typical objects I worked on were six or seven magnitudes fainter. No wonder I didn't know how long to expose it," he says. His first attempt, on December 27, was so overexposed as to be useless, but he got it right the second time two nights later.

When this plate was developed, it showed four nice, fat lines that, once again, didn't match anything. The mystery remained for about six weeks, until Schmidt was invited by Parkes Observatory director John Bolton (who had overseen the construction of Caltech's Owens Valley facility a few years earlier) to submit a paper to Nature to go with the one that Hazard and company were preparing on 3C 273's position.

And so it was that after lunch on Monday, February 5, 1963, Schmidt was sitting in his office trying once again to make sense of his results. He popped the plate into the viewer, and it suddenly dawned on him that three of his lines, plus one in the infrared that Associate Professor of Astronomy J. Beverley Oke had found using the 100-inch telescope on Mount Wilson, formed a series whose spacing and intensity decreased uniformly from red to blue.

The Balmer series, the best-known set of lines in hydrogen's emission spectrum, does exactly the same thing, but there was one small problem with applying that explanation to 3C 273: the brightest line in the Balmer series, known as H-alpha, is red. As in visible red, not infrared. The wavelength of Oke's line was too far into the infrared by a factor 15.8 percent. However, the brightest, reddest line on Schmidt's plate was in the correct spot for H-beta, the second line in the Balmer series—if its wavelength were also 15.8 percent shorter; H-beta is normally cyan in color. A redshift of 15.8 percent is equivalent to a distance of about three billion light-years in the currently accepted scale of the universe. That's billion. With a 'B.' Our galaxy, the Milky Way, is a mere 120,000 or so light-years in diameter. And Andromeda, our nearest galactic neighbor of any consequence, is only about 2.5 million light-years away. By great good luck, the spectrum of 3C 273 was redshifted by a small enough amount that the Balmer spectrum was still recognizable, but yet redshifted enough to place it really, really far beyond our galaxy.

In his excitement, Schmidt began pacing the hallway, where he buttonholed Professor of Astrophysics Jesse Greenstein. Greenstein had been puzzling over a similar object, 3C 48, whose position had been worked out in 1960 by Matthews and Allan Sandage at the Carnegie Observatories up the street from Caltech. They had found a 16th-magnitude variable blue star, whose spectra, taken by Greenstein and Professor of Astronomy Guido Münch, had the usual assortment of unidentifiable emission lines. Greenstein pulled out the unpublished paper he was working on, and, as Schmidt recalled in his oral history, "in about five or seven minutes, we found a redshift of thirty-seven percent. . . They mutually confirmed each other."

The hubbub attracted Oke, and for the rest of the afternoon the three astronomers tried to come up with an alternative explanation—some weirdly ionized states of relatively rare elements, perhaps—that would allow these "stars" to remain comfortably in our own galaxy. When six o'clock rolled around and no other solution had presented itself, they decided to call it a day. But rather than heading home as usual, "we all trooped with Jesse to his house," Schmidt continued. "And Naomi [Greenstein, Jesse's wife] was immensely surprised, because we all wanted a drink. I came home late that night, and I think I said to my wife, 'Something terrible happened at the office.' It's not necessarily the right expression, but that's what I said."

The "terrible" part was that if 3C 273 really was three billion light-years away, it had to be shining 40 times more brightly than the brightest galaxies. Explaining how this could happen would have to wait until 1969, when a former postdoc of Schmidt's, Donald Lynden-Bell at the University of Cambridge, showed that material swirling around a black hole at a galaxy's center could radiate such staggering amounts of energy before being sucked down the drain.

On March 16, 1963, Nature published four articles back-to-back. The first, by the Parkes people, described the radio observations of 3C 273. The second, by Schmidt, announced the redshift. The third was by Oke about his infrared observations, and the final one, by Greenstein and Matthews, presented the corroborating redshift of 3C 48.

In his article, which was all of two-thirds of a page long, Schmidt noted that it was possible that 3C 273 could be a star in our own galaxy, but that "it would be extremely difficult, if not impossible, to account for" its peculiar spectrum, and that "the explanation in terms of an extragalactic origin seems most direct and least objectionable."

The papers referred to 3C 273 and 3C 48 as "star-like objects," for lack of a better term. Over the next few months, as more of them were discovered and it became abundantly clear that they were not stars, they began to be referred to as "quasi-stellar radio sources," or QSRs. The term "quasar" was coined by Hong-yee Chiu of NASA's Goddard Institute for Space Studies in a May 1964 article for Physics Today.

In 1965 Schmidt published a paper on five quasars, one of which had a redshift of 2.01, placing it halfway across the visible universe. And since distance and age are the same in astronomy, these very, very far-off objects give us an inkling of what the very, very young universe was like. Ever since the '60s, quasar studies have helped us map the universe, figure out why it is as it is today, and even work out how it all began. "The night I discovered the redshift, it was a fantastic prospect," says Schmidt. "We could now easily get to very large redshifts, because these darn things are so bright."

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Douglas Smith
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Two Decades of Discoveries

Keck Observatory marks 20th anniversary

Although Keith Matthews was about to make history, he went about his tasks like any others. It was the night of March 16, 1993, nearly 14,000 feet above sea level on Mauna Kea in Hawaii, and he had just installed the first instrument on the brand-new 10-meter telescope at W. M. Keck Observatory. Matthews, who built the instrument—a near-infrared camera, abbreviated NIRC—was set to make the first scientific observations using the newly crowned Biggest Telescope in the World.

This Saturday marks the 20th anniversary of those inaugural observations. Speaking at a symposium on March 7 commemorating the anniversary, Tom Soifer, chair of the Division of Physics, Mathematics and Astronomy, called those initial observations "one of the greatest events in astronomy. It's been a remarkable 20 years of exploration and discovery," he said.

At the time of that first observing run, the telescope had yet to be officially commissioned and wasn't yet optimized, but Matthews—now chief instrument scientist at Caltech—was there to see just what the telescope could do. "Fortunately, it worked right off the bat," he recalls.

The observatory was the culmination of more than a decade of planning, designing, and building made possible by unprecedented financial contributions from the Keck Foundation ($70 million for the first telescope) and by cutting-edge technology. But Matthews didn't feel much reason to jump for joy when he saw that first star, sharp and bright on the computer screen. He was too busy to be excited, he says, and those observations were just another set of steps in a long process that had begun more than a decade prior, when he joined the telescope design team in 1979. Caltech would become an official partner of the observatory in 1985, joining the University of California and the University of Hawaii (NASA would join in 1996).

To be sure, Matthews was happy that everything was working relatively smoothly. But, he says, throughout the whole process of making the telescope and the instrument a reality, there was always something else that he needed to focus on and get done. He was observing alone—a rarity these days—operating on four hours of sleep for roughly nine nights. He slept at 9,000 feet and had to make the drive up the summit into the sun's glare every day. The altitude at the summit made the work even more grueling.

And there were still the inevitable bugs and problems. For one, the Dewar—the container that housed the infrared camera and kept it cold—was leaking liquid helium. Matthews tried everything from rubber cement to glycerol to control the leak. The computers also kept crashing, the monitors going blank one by one. "It was funny," he recalls. "All the screens started to go like a house of cards."

He eventually found stopgap measures to control the leak, and the computers were simply rebooted. The observing run demonstrated that even before the telescope was fully optimized, it was already able to achieve better resolution than the 200-inch Hale Telescope at Palomar Observatory, supplanting the 200-inch as the world's most powerful telescope—a title the 200-inch had held since 1948. A second, identical Keck telescope was built in 1996.

In the two decades since, Keck has become arguably the most prominent and productive observatory in astronomy, helping scientists learn how the universe has evolved since the Big Bang, how galaxies form, and how stars are born. The twin telescopes, Keck I and Keck II, have studied dark matter—the mysterious, unseen stuff that makes up most of the universe's mass—as well as dark energy, the cosmic force that's pushing the universe apart. The telescopes have peered into other planetary systems and revealed insights into the origin of our own solar system. In describing how Keck has surpassed expectations, Caltech's Richard Ellis said at last week's symposium, "Unlike politicians, astronomers deliver much more than they predicted."

The symposium highlighted the fact that Keck has proved indispensible, as a powerful telescope in its own right and as an essential complement to other telescopes. "Keck has been fundamental in establishing partnerships with space telescopes," Ellis said. For example, he has used Keck with the Hubble Space Telescope and the Spitzer Space Telescope to probe some of the most distant galaxies ever observed, revealing a poorly understood period of cosmic history roughly a billion years after the Big Bang. With the help of Keck, Fiona Harrison—a Caltech astronomer and principal investigator of the NuSTAR mission, a space telescope that detects high-energy X rays—discovered bright flares emanating from the supermassive black hole at the center of the galaxy. The flares, she said, could be due to asteroids being ripped apart by the black hole.

And even though NASA's Kepler Space Telescope has been revolutionary in identifying thousands of candidate planets, a ground-based telescope like Keck is needed to verify and characterize those worlds. Caltech's John Johnson, for example, has used Keck to characterize what he says are the most typical kind of planetary system in the galaxy. From his analysis, he estimates that there are at least 100 billion planets in the Milky Way. Keck has also allowed Caltech's Mike Brown to measure detailed spectra of Jupiter's moon Europa, finding evidence that suggests its subsurface ocean may bubble up to its frozen surface.

Of course, none of these discoveries would have been possible without Keck's technological advances. Constructing a telescope as large as Keck using a single mirror would be prohibitively expensive and difficult to engineer. Instead, the Keck telescopes each consist of 36 hexagonal mirrors, forming a total aperture of 10 meters. No one had ever attempted a segmented-mirror telescope before Keck. Ellis was at Cambridge University while the telescope was being developed. "We were looking at this plan with total incredulity," he recalled at the symposium. "The idea of a finely segmented telescope was crazy to us, frankly."

One of the difficulties, for example, was in polishing the mirrors. Because a spherical mirror has rotational symmetry, it's relatively easy to polish. But because each of Keck's segments forms just a part of a parabolic curve, each mirror is asymmetrical, making it near impossible to polish. The solution? Force each segment into a spherical shape. Once polished, the mirror is released and pops back into its original, irregular form.

The telescope is fitted with a suite of instruments that have been constantly upgraded and replaced over the last 20 years—and Caltech has played leading roles with many of those instruments, including NIRC and NIRC2 (the second-generation NIRC) and MOSFIRE (co-led by Caltech's Chuck Steidel), a new spectrometer that was just installed last year. Matthews was also the leader on NIRC2, played a significant role in MOSFIRE, and is now leading the effort on a new instrument, a near-infrared spectrometer called NIRES.

As technology improves, telescopes get bigger and more powerful. Keck's eventual replacement, the Thirty Meter Telescope (TMT), in which Caltech is a partner, won't be ready for at least 10 years. In the meantime, Keck will continue to hold its status as the biggest telescope in the world. And, as Caltech's Judith Cohen pointed out in her symposium talk, even after the TMT is built Keck will remain a useful facility—in much the same way that Palomar Observatory remains productive more than 60 years after it was built. In the last two decades, Keck has had a good run in helping astronomers explore the cosmos—but that run is far from over.

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Marcus Woo
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Bursts of Star Formation in the Early Universe

PASADENA, Calif.—Galaxies have been experiencing vigorous bursts of star formation from much earlier in cosmic history than previously thought, according to new observations by a Caltech-led team.

These so-called starburst galaxies produce stars at a prodigious rate—creating the equivalent of a thousand new suns per year. Now the astronomers have found starbursts that were churning out stars when the universe was just a billion years old. Previously, astronomers didn't know whether galaxies could form stars at such high rates so early in time.

The discovery enables astronomers to study the earliest bursts of star formation and to deepen their understanding of how galaxies formed and evolved. The team describes their findings in a paper being published online on March 13 in the journal Nature and in two others that have been accepted for publication in the Astrophysical Journal.

Shining with the energy of over a hundred trillion suns, these newly discovered galaxies represent what the most massive galaxies in our cosmic neighborhood looked like in their star-making youth. "I find that pretty amazing," says Joaquin Vieira, a postdoctoral scholar at Caltech and leader of the study. "These aren't normal galaxies. They were forming stars at an extraordinary rate when the universe was very young—we were very surprised to find galaxies like this so early in the history of the universe."

The astronomers found dozens of these galaxies with the South Pole Telescope (SPT), a 10-meter dish in Antarctica that surveys the sky in millimeter-wavelength light—which is between radio waves and infrared on the electromagnetic spectrum. The team then took a more detailed look using the new Atacama Large Millimeter Array (ALMA) in Chile's Atacama Desert.

The new observations represent some of ALMA's most significant scientific results yet, Vieira says. "We couldn't have done this without the combination of SPT and ALMA," he adds. "ALMA is so sensitive, it is going to change our view of the universe in many different ways."

The astronomers only used the first 16 of the 66 dishes that will eventually form ALMA, which is already the most powerful telescope ever constructed for observing at millimeter and submillimeter wavelengths.

With ALMA, the astronomers found that more than 30 percent of the starburst galaxies are from a time period just 1.5 billion years after the big bang. Previously, only nine such galaxies were known to exist, and it wasn't clear whether galaxies could produce stars at such high rates so early in cosmic history. Now, with the new discoveries, the number of such galaxies has nearly doubled, providing valuable data that will help other researchers constrain and refine theoretical models of star and galaxy formation in the early universe.

But what's particularly special about the new findings, Vieira says, is that the team determined the cosmic distance to these dusty starburst galaxies by directly analyzing the star-forming dust itself. Previously, astronomers had to rely on a cumbersome combination of indirect optical and radio observations using multiple telescopes to study the galaxies. But because of ALMA's unprecedented sensitivity, Vieira and his colleagues were able make their distance measurements in one step, he says. The newly measured distances are therefore more reliable and provide the cleanest sample yet of these distant galaxies.

The measurements were also made possible because of the unique properties of these objects, the astronomers say. For one, the observed galaxies were selected because they could be gravitationally lensed—a phenomenon predicted by Einstein in which another galaxy in the foreground bends the light from the background galaxy like a magnifying glass. This lensing effect makes background galaxies appear brighter, cutting the amount of telescope time needed to observe them by 100 times.

Secondly, the astronomers took advantage of a fortuitous feature in these galaxies' spectra—which is the rainbow of light they emit—dubbed the "negative K correction." Normally, galaxies appear dimmer the farther away they are—in the same way a lightbulb appears fainter the farther away it is. But it turns out that the expanding universe shifts the spectra in such a way that light in millimeter wavelengths doesn't appear dimmer at greater distances. As a result, the galaxies appear just as bright in these wavelengths no matter how far away they are—like a magic lightbulb that appears just as bright no matter how distant it is.

"To me, these results are really exciting because they confirm the expectation that when ALMA is fully available, it can really allow astronomers to probe star formation all the way up to the edge of the observable universe," says Fred Lo, who, while not a participant in the study, was recently a Moore Distinguished Scholar at Caltech. Lo is a Distinguished Astronomer and Director Emeritus at the National Radio Astronomy Observatory, the North American partner of ALMA.

Additionally, observing the gravitational lensing effect will help astronomers map the dark matter—the mysterious unseen mass that makes up nearly a quarter of the universe—in the foreground galaxies. "Making high-resolution maps of the dark matter is one of the future directions of this work that I think is particularly cool," Vieira says.

These results represent only about a quarter of the total number of sources discovered by Vieira and his colleagues with the SPT, and they anticipate finding additional distant, dusty, starburst galaxies as they continue analyzing their data set. The ultimate goal for astronomers, Lo says, is to observe galaxies at all wavelengths throughout the history of the universe, piecing together the complete story of how galaxies have formed and evolved. So far, astronomers have made much progress in creating computer models and simulations of early galaxy formation, he says. But only with data—such as these new galaxies—will we ever truly piece together cosmic history. "Simulations are simulations," he says. "What really counts is what you see."

In addition to Vieira, the other Caltech authors on the Nature paper are Jamie Bock, professor of physics; Matt Bradford, visiting associate in physics; Martin Lueker-Boden, postdoctoral scholar in physics; Stephen Padin, senior research associate in astrophysics; Erik Shirokoff, a postdoctoral scholar in astrophysics with the Keck Institute for Space Studies; and Zachary Staniszewski, a visitor in physics. There are a total of 70 authors on the paper, which is titled "High-redshift, dusty, starburst galaxies revealed by gravitational lensing." This research was funded by the National Science Foundation, the Kavli Foundation, the Gordon and Betty Moore Foundation, NASA, the Natural Sciences and Engineering Research Council of Canada, the Canadian Research Chairs program, and the Canadian Institute for Advanced Research.

The work to measure the distances to the galaxies is described in the Astrophysical Journal paper "ALMA redshifts of millimeter-selected galaxies from the SPT survey: The redshift distribution of dusty star-forming galaxies," by Axel Weiss of the Max-Planck-Institut für Radioastronomie, and others. The study of the gravitational lensing is described in the Astrophysical Journal paper "ALMA observations of strongly lensed dusty star-forming galaxies," by Yashar Hezaveh of McGill University, and others.

ALMA, an international astronomy facility, is a partnership of Europe, North America, and East Asia in cooperation with the Republic of Chile. ALMA construction and operations are led on behalf of Europe by the European Southern Observatory (ESO) organization, on behalf of North America by the National Radio Astronomy Observatory (NRAO), and on behalf of East Asia by the National Astronomical Observatory of Japan (NAOJ). The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning, and operation of ALMA.

The South Pole Telescope (SPT) is a 10-meter telescope located at the National Science Foundation (NSF) Amundsen-Scott South Pole Station, which lies within one kilometer of the geographic south pole. The SPT is designed to conduct low-noise, high-resolution surveys of the sky at millimeter and submillimeter wavelengths, with the particular design goal of making ultrasensitive measurements of the cosmic microwave background (CMB). The first major survey with the SPT was completed in October 2011 and covers 2,500 square degrees of the southern sky in three millimeter-wave observing bands. This is the deepest large millimeter-wave data set in existence and has already led to many groundbreaking science results, including the first detection of galaxy clusters through their Sunyaev-Zel'dovich effect signature, the most sensitive measurement yet of the small-scale CMB power spectrum, and the discovery of a population of ultrabright, high-redshift, star-forming galaxies. The SPT is funded primarily by the Division of Polar Programs in NSF's Geoscience Directorate. Partial support also is provided by the Kavli Institute for Cosmological Physics (KICP), an NSF-funded Physics Frontier Center; the Kavli Foundation; and the Gordon and Betty Moore Foundation. The SPT collaboration is led by the University of Chicago and includes research groups at Argonne National Laboratory, the California Institute of Technology, Cardiff University, Case Western Reserve University, Harvard University, Ludwig-Maximilians-Universität, the Smithsonian Astrophysical Observatory, McGill University, the University of Arizona, the University of California at Berkeley, the University of California at Davis, the University of Colorado at Boulder, and the University of Michigan, as well as individual scientists at several other institutions, including the European Southern Observatory and the Max-Planck-Institut für Radioastronomie in Bonn, Germany.

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Marcus Woo
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Astronomers Observe Planets Around Another Star Like Never Before

New instrument reveals exotic nature of four planets orbiting the same nearby star

PASADENA, Calif.—Thanks to a new high-tech gadget, astronomers have observed four planets orbiting a star relatively close to the sun in unprecedented detail, revealing the roughly ten-Jupiter-mass planets to be among the most exotic ones known.

The team, which includes several researchers from the California Institute of Technology (Caltech), describes its findings in a paper accepted for publication by the Astrophysical Journal.

The findings were made possible by a first-of-its-kind telescope imaging system that allowed the astronomers to pick out the planets amidst the bright glare of their parent star and measure their spectra—the rainbows of light that reveal the chemical signatures of planetary atmospheres. The system, dubbed Project 1640, enables astronomers to observe and characterize these kinds of planetary systems quickly and routinely, which has never been done before, the researchers say.

"These warm, red planets are unlike any other known objects in our universe," says Ben R. Oppenheimer, an astronomer at the American Museum of Natural History and the paper's lead author. And the planets are very different from one another as well. "All four planets have different spectra and all four are peculiar."

Astronomers had previously taken images of these four planets, which orbit a star called HR 8799, located 128 light years away. But because a star's light is tens of millions to billions of times brighter than the light from that star's own planets, distinguishing planet light from starlight so as to directly measure the spectra from the planets alone is difficult. "It's like taking a single picture of the Empire State Building from an airplane that reveals the height of the building but also a bump on the sidewalk next to it that is as high as a couple of bacteria," Oppenheimer explains. "Furthermore, we've been able to do this over a range of wavelengths in order to make a spectrum."

In the past, astronomers have been able to take spectra of some planets that pass in front of, or transit, their stars. But with Project 1640, which uses the Hale Telescope at Caltech's Palomar Observatory in Southern California, astronomers can now take the direct spectra of planets orbiting other stars—called exoplanets—that are not transiting. The device blocks the otherwise overwhelming starlight, picks out the faint specks that are planets, and obtains their spectra.  Project 1640 allowed the team to take spectra of all four of the planets around HR 8799 simultaneously, which had never been done for any planetary system before.  

The planets around HR 8799 are at about the same distance from that star as the solar system's gas giants (Jupiter, Saturn, Uranus, and Neptune) are from our sun. But since it's easier to detect transiting planets that are close to their stars, the transiting systems that astronomers have observed have small orbits—often smaller than Mercury's. The new results, therefore, represent the first spectra to be taken of gas giants located so far from their stars—a distance at which the influence of the stars' radiation, flares, and other features are weaker.

"We are now technically capable of obtaining spectra of giant planets in planetary systems like our own, improving on the close-in transiting planet studies done previously," says Lynne Hillenbrand, professor of astronomy at Caltech and a coauthor of the paper. And what the spectra show is that the planets are quite strange. "A remarkable thing about these planets is their unexpected spectroscopic diversity," Hillenbrand says.

One of the most striking abnormalities is an apparent chemical imbalance. Under most circumstances, ammonia and methane should naturally coexist in a planet's atmosphere—where there is one, there is usually the other—unless they are generated in extremely cold or hot environments. Yet the spectra of the HR 8799 planets, all of which have "lukewarm" temperatures of about 1000 Kelvin (1340 degrees Fahrenheit), either have methane or ammonia alone, with little or no sign of their chemical partner. There is also evidence of other chemicals such as acetylene—which has never before been detected on any exoplanet—and carbon dioxide.

The planets also are "redder"—they emit longer wavelengths of light—than celestial objects with similar temperatures. This could be explained by the presence of significant but patchy cloud cover on the planets, the authors say.

HR 8799 itself is very different from our sun, with 1.6 times its mass and five times its brightness. The brightness of this distant star can vary by as much as 8 percent over a period of two days; it produces about 1,000 times more ultraviolet light than the sun. All of these factors could induce complex weather and sooty hazes that would, in turn, cause periodic changes in the spectra.

More data are needed to further explore this solar system's unusual characteristics, the scientists say.

"The spectra of these four worlds clearly show that they are far too toxic and hot to sustain life as we know it," says coauthor Ian Parry, a senior lecturer at the Institute of Astronomy, Cambridge University. "But the really exciting thing is that, one day, the techniques we've developed will give us our first secure evidence of the existence of life on a planet outside our solar system."

The techniques used by Project 1640 require the coordinated operation of four major instruments: the world's most advanced adaptive-optics system, which can make millions of tiny adjustments to the device's two six-inch mirrors every second; a coronagraph that optically dims the star but not other celestial objects in the field of view; an imaging spectrograph that records 30 images in a rainbow of colors simultaneously; and a specialized wavefront sensor that distinguishes between residual starlight that sneaks through the coronagraph and light from planets, allowing scientists to filter out background starlight more effectively.

With these instruments working in concert, the project is able to reveal celestial objects 1 million to 10 million times fainter than the star at the center of one of its images, with only an hour of observations. It is also capable of measuring the orbital motion of objects.

"Our young century has seen seminal advances in exoplanet science, but almost exclusively from indirect observations," says Richard Dekany, a coauthor and associate director for development for Caltech Optical Observatories. "Project 1640 has now added to this revolution the scientific gold standard: directly measured spectra of young giant planets. Our initial findings suggest each of these strange and wonderful giant planets may have a unique story to share."

The researchers are already collecting more data on this system so as to look for changes in the planets over time; they are also surveying other young stars. During its three-year survey at Palomar, which started in June, Project 1640 aims to survey 200 stars within about 150 light years of our solar system.

"In the 19th century, it was thought impossible to know the composition of stars, but the invention of astronomical spectroscopy has revealed detailed information about nearby stars and distant galaxies," says Charles Beichman, executive director of the NASA Exoplanet Science Institute at Caltech. "Now, with Project 1640, we are beginning to turn this tool to the investigation of neighboring exoplanets to learn about the composition, temperature, and other characteristics of their atmospheres."

The title of the the Astrophysical Journal paper is "Reconnaissance of the HR 8799 exosolar system I: Near IR spectroscopy." In addition to Hillenbrand, Dekany, and Beichman, the other Caltech authors are postdocs Christoph Baranec and Sasha Hinkley; former postdoc Justin Crepp (now at the University of Notre Dame); and programmer David Hale, along with a similar number of JPL authors. This work was supported by the National Science Foundation and NASA. Additional funding sources for Project 1640 are listed here.

This story is adapted from a press release by Kendra Snyder of the American Natural History Museum.

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Marcus Woo
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Ryan Patterson Awarded Sloan Research Fellowship

Ryan Patterson, assistant professor of physics at Caltech, is one of 126 young scholars to receive a Sloan Research Fellowship for 2013.

According to the Alfred P. Sloan Foundation, the purpose of the Sloan Research Fellowships is to "stimulate fundamental research by early-career scientists and scholars of outstanding promise." Candidates are nominated by their fellow scientists and chosen by an independent panel of senior scholars. Fellows receive $50,000 to be used to further their research.

"I feel very honored and am thankful to the Alfred P. Sloan Foundation for this fellowship," says Patterson. "The fellowship will be a great help to my research efforts here at Caltech."

Patterson conducts research in particle physics, with a particular focus on elementary subatomic particles known as neutrinos. His research group at Caltech is centrally involved in the Fermilab MINOS and NOvA experiments, which study the characteristics of neutrinos.

Patterson received his BS from Caltech in 2000 and his PhD from Princeton in 2007, then returned to Caltech as an assistant professor 2010. He also recently received an Early Career Research Award from the Department of Energy Office of Science.

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Viewing the Cosmos from the South Pole: An Interview with Jamie Bock

Almost immediately after the Big Bang—roughly after ten trillionths of a trillionth of a trillionth of a second—the universe suddenly grew. Very fast. The entire cosmos, which at the time was smaller than an atom, expanded to the size of a beach ball in less than a millionth of a trillionth of a trillionth of a second—before settling down to a more leisurely rate of growth that continues to this day.

The early universe was filled with energy, and quantum mechanical fluctuations led to tiny variations in its density. Thanks to that rapid early expansion—called inflation—those small quantum fluctuations over time stretched to vast scales, forming cosmic structures like galaxies and galaxy clusters. Inflation stretched space faster than photons can travel, flinging apart different regions of the universe. This means there may be distant parts of the cosmos whose photons are still trying to reach us—and the universe we can see now may be just a tiny fraction of a much larger universe.

But what exactly triggered cosmic inflation? Scientists like Jamie Bock are trying to answer that question and others about what the universe was like during those first moments of existence. Bock is part of Caltech's experimental cosmology group, which devises new kinds of detectors, telescopes, and experiments to study the cosmic microwave background—the Big Bang's afterglow, which fills the entire sky. Bock—who is no stranger to Caltech, as he has been affiliated with the university and JPL since 1994—joined the faculty in the fall. He recently answered some questions about his work.

What are you trying to learn?

We're searching for signatures from the time of inflation. And there's good evidence that a process like inflation happened in the moments after the Big Bang. For example, BOOMERanG, a balloon-borne experiment developed at Caltech, made a measurement in 2000 showing that the geometry of the universe is flat to within experimental precision. Flatness is a fundamental prediction of inflation. This tremendous expansion has taken whatever intrinsic geometry existed before inflation, and by stretching it out, makes the universe now appear flat.

While we know something like inflation happened in the early universe, we don't understand the physics behind it. Conventional wisdom says that inflation is related to exotic physics from some yet-to-be-understood grand unification theory, at energies well beyond what we can probe with particle accelerators on Earth. The exciting thing is that we are now making tests with the microwave background to pin down what exactly  causes inflation.

In particular, inflation makes a background of gravitational waves—ripples in space and time that are still lurking in the universe today. The amplitude of the gravitational-wave background is sensitive to the physical process behind inflation. These gravitational waves make a very small—possibly detectable—polarization signal in the microwave background. If we can detect this polarization signal, or even put a useful upper limit on it, we start to put constraints on what kind of physics caused inflation.

What kind of research does your group do?

I lead an experimental group that builds unique instruments for looking at the early universe. For studying the cosmic microwave background, we have a balloon experiment called Spider—which is a successor to BOOMERanG—that's searching for the polarization signal from inflation. We also have an experiment called the Keck polarimeter array, funded by the Keck Foundation, presently carrying out similar measurements from the South Pole.

Our group has a long affiliation with the Herschel and Planck satellites, which began with the building of focal-plane detectors at JPL, and both have now produced spectacular data that our group is helping to analyze. Planck is coming out with its first cosmology results this year.            

More recently, I've gotten interested in slightly later times in the universe, borrowing techniques from our studies of the microwave background to study the extragalactic background light, a diffuse haze of light produced by early galaxies. Instead of detecting galaxies individually, which would require an enormous telescope, we can study the spatial variations made by many galaxies in this background haze. We can do this with a small telescope, a very efficient way to make observations, and the latest idea we're after is to make images at multiple wavelengths with an imaging spectrometer. Ultimately we hope to learn about the epoch of reionization, a period when the first galaxies started shining.

The Spider, BOOMERanG, and the Keck polarimeter array experiments have all been performed in Antarctica. Do you go often? What kind of work do you and your colleagues do there?

I've been to the pole four times during the summer myself, and some members of the group have wintered over. This year, we're making upgrades to the Keck array, testing the experiment, doing calibrations and measurements. Typically by the end of the season, we're back to observing the sky's microwave background. The station is closed from mid-February to October, and there are no flights in or out during the winter. We leave one person for the winter season to operate the experiment. Next year we plan to launch the SPIDER balloon experiment, which will fly in a circle around the continent during the Antarctic summer season.

What's the South Pole like?

The South Pole is a lot of fun, kind of like a summer camp for scientists. There are social activities every week—volleyball, pub trivia, and bingo night are my favorites. Satellite coverage for email is limited to eight hours a day, so you don't have a lot of distractions. Everything's provided, with great food, a gym, and even a greenhouse. Every morning you put on your winter gear and walk out across the airfield to the laboratory.

Right around now it would typically be about –30°F, a relatively balmy summer temperature. In the winter, it typically goes below –100°F at some point. Even in the summer you have to cover your whole body. The first breath is always a shock coming off the airplane. Some of the shock is due to the fact that the South Pole is at an altitude of 10,000 feet, standing atop two miles of ice. The air's thinner and it's a lot colder than when you get on the plane at the edge of the continent at sea level.

What have you enjoyed about being at Caltech and JPL?

I really value both institutions, and there's a great synergy between them. Caltech has fantastic students and postdocs, and combining their enthusiasm and drive with JPL's world-class professionals and technologies is a truly powerful combination. Working between the two institutions brings a world of new opportunities.

Bock grew up in Ohio before going to Duke University, where he received his BS in physics and math in 1987. He then went to UC Berkeley—where the late Caltech astrophysicist Andrew Lange was his advisor—for his MA and PhD in physics in 1990 and 1994, respectively. Bock then joined JPL as a postdoc, and has since held research positions at JPL and a visiting appointment at Caltech. He's now a professor of physics at Caltech.

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Marcus Woo
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Caltech Senior Wins Churchill Scholarship

Caltech senior Andrew Meng has been selected to receive a Churchill Scholarship, which will fund his graduate studies at the University of Cambridge for the next academic year. Meng, a chemistry and physics major, was one of only 14 students nationwide who were chosen to receive the fellowship this year.

Taking full advantage of Caltech's strong tradition of undergraduate research, Meng has worked since his freshman year in the lab of Nate Lewis, the George L. Argyros Professor and professor of chemistry. Over the course of three Summer Undergraduate Research Fellowships (SURFs) and several terms in the lab, Meng has investigated various applications of silicon microwire solar cells. Lewis's group has shown that arrays of these ultrathin wires hold promise as a cost-effective way to construct solar cells that can convert light into electricity with relatively high efficiencies.

Meng, who grew up in Baton Rouge, Louisiana, first studied some of the fundamental limitations of silicon microwires in fuel-forming reactions. In these applications, it is believed that the microwires can harness energy from the sun to drive chemical reactions such as the production of hydrogen and oxygen from splitting water. Meng's work showed that the geometry of the microwires would not limit the fuel-forming reaction as some had expected.

More recently, Meng has turned his attention to using silicon microwires to generate electricity. He is developing an inexpensive electrical contact to silicon microwire chips, using a method that facilitates scale-up and can be applied to flexible solar cells.

"Andrew is one of the best undergraduates that I have had the pleasure of working with in over a decade," says Lewis. "He excels in academics, in leadership, and in research. I believe he is truly worthy of the distinction of receiving a Churchill Fellowship. " 

As he pursues a Master of Philosophy degree in chemistry at the University of Cambridge over the next year, Meng will work in the group of theoretical chemist Michiel Sprik. He plans to apply computational methods to his studies of fuel-forming reactions using solar-energy materials.

"I'm very grateful for this opportunity to learn a computational perspective, since up until now I've been doing experimental work," Meng says. "I'm very excited, and most importantly, I'd like to thank Caltech and all of my mentors and co-mentors, without whom I would not be in this position today."

According to the Winston Churchill Foundation's website, the Churchill Scholarship program "offers American citizens of exceptional ability and outstanding achievement the opportunity to pursue graduate studies in engineering, mathematics, or the sciences at Cambridge. One of the newer colleges at the University of Cambridge, Churchill College was built as the national and Commonwealth tribute to Sir Winston, who in the years after the Second World War presciently recognized the growing importance of science and technology for prosperity and security. Churchill College focuses on the sciences, engineering, and mathematics." The first Churchill Scholarships were awarded in 1963, and this year's recipients bring the total to 479 Churchill Scholars.

Each year, a select group of universities, including Caltech, is eligible to nominate students for consideration for the scholarship. Meng is the seventh Caltech student to have won the award since the year 2000. A group of Caltech faculty members and researchers work with Lauren Stolper, director of fellowships advising, to identify and nominate candidates. This year, the members of the group were Churchill Scholar alumni John Brady, the Chevron Professor of Chemical Engineering and professor of mechanical engineering; Mitchio Okumura, professor of chemical physics; Alan Cummings, senior research scientist; and Eric Rains, professor of mathematics.

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Kimm Fesenmaier
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John Johnson Wins Astronomy Prize

John A. Johnson, assistant professor of planetary astronomy at Caltech, received the 2012 Newton Lacy Pierce Prize at the 221st meeting of the American Astronomical Society (AAS), in Long Beach, California.

The AAS reserves the Newton Lacy Pierce Prize for North American astronomers, ages 36 and under, for "outstanding achievement, over the past five years, in observational astronomical research based on measurements of radiation from an astronomical object." Johnson received a cash award and an invitation to speak at the AAS conference on January 8.

According to the award citation, Johnson was recognized for "major contributions to understanding fundamental relationships between exosolar planets and their parent stars, including finding a variety of orientations between planetary orbital planes and the spin axes of their stars, developing a rigorous understanding of planet detection rates in transit and direct imaging experiments, and examining possible correlations between planet frequency and the mass and metallicity of their host stars."

"I am very pleased and thankful to the American Astronomical Society for this award," Johnson says. "Thanks to powerful new instruments and an emerging generation of highly motivated explorers, planetary astronomy is an exciting field to be in right now. I am happy to be part of it."

Johnson is one of the founding members of Caltech's new Center for Planetary Astronomy. His recent research findings related to the estimated number of planets in the Milky Way have generated significant interest both within the astronomical community and among the general public.

In addition to the Pierce Prize, Johnson was also a recipient in 2012 of a Lyman Spitzer Lectureship, an Alfred P. Sloan Research Fellowship, and a David and Lucile Packard Fellowship.

 

 

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Friday, January 25, 2013
Annenberg 121

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