Remembering Tom Tombrello

1936–2014

Thomas Anthony Tombrello, Caltech's Robert H. Goddard Professor of Physics, passed away on September 23, 2014, at age 78. His studies of nuclear reactions in the 1960s helped show how chemical elements are created.

Tombrello was known on campus as a devoted teacher. "Probably his greatest contribution to Caltech was the identification and mentoring of generations of promising undergraduate physicists," says Steven Koonin (BS '72), Caltech's provost from 1995 to 2004 and now director of the Center for Urban Science and Progress at New York University. "I was among the first of those."

"Tom was incredibly enthusiastic, supportive, and generous with his time with my cohort of undergrads, and he kept this up for the next 40 years," says Joe Polchinski (BS '75), a string theorist at the Kavli Institute for Theoretical Physics at UC Santa Barbara.

"Tom counseled me in all aspects of graduate student life—from classes and instructors to the more personal challenges that students face," says France Córdova (PhD '79), the director of the National Science Foundation. "He remained a lifelong friend and counselor. I was buoyed by his email messages, such as the one that followed the announcement of my current position: 'These will be trying times, but you are up to the challenge. If there is any way I can be of help, please let me know.' This was characteristic of his ready support."

Tombrello was born in Austin, Texas, on September 20, 1936. He attended Rice Institute (now Rice University), earning his BA, MA, and PhD in physics in 1958, 1960, and 1961, respectively, before coming to Caltech as a postdoctoral fellow in 1961. He accepted an assistant professorship at Yale in 1963, but returned to Caltech a year later and resumed his research with William Fowler (PhD '36) in the W. K. Kellogg Radiation Laboratory. Fowler and his colleagues had predicted that certain isotopes of lithium, beryllium, boron, carbon, nitrogen, oxygen, and fluorine would be produced as sun-like stars burned their nuclear fuel. Tombrello synthesized many of these isotopes in Kellogg's megavolt particle accelerator and recorded their spectra, allowing astronomers to measure their stellar abundances and confirm that they appeared in the predicted proportions. He was promoted to assistant professor in 1965, associate professor in 1967, and full professor in 1971.

In 1973, Tombrello took over as principal investigator on the main grant supporting the Kellogg lab, just as money for nuclear physics began to dry up. With some 50 faculty, students, and staff to support, he found other funding by broadening Kellogg's scope of work. He used the particle accelerator to bombard lunar rocks with heavy ions to replicate conditions on the lunar surface and ventured into materials science by conducting radiation-damage studies for the China Lake Naval Weapons Center.

In 1986, Tombrello was put in charge of the physics staffing committee, where he helped hire new physics faculty, according to David Morrisroe Professor of Physics Ed Stone, then the division chair for Physics, Mathematics, and Astronomy.

From 1987 to 1989, Tombrello took a leave of absence from Caltech to become vice president and director of research for Schlumberger-Doll, an oil-industry service company.

Tombrello chaired the Division of Physics, Mathematics and Astronomy from 1998 to 2008. Says Koonin, "I was provost for the majority of that time, and we worked well together, although not without productive tensions. He was an energetic, strategic thinker who advanced the division through hires in quantum optics, string theory, nanotechnology, and space-based X-ray and ultraviolet astronomy." But their "greatest collaborative effort," Koonin says, was the Thirty Meter Telescope, which when completed in the early 2020s, will be the world's most advanced optical and near-infrared observatory.

Tombrello oversaw several other projects during his tenure as division chair. He was deeply involved in the design and construction of the Cahill Center for Astronomy and Astrophysics. He helped establish what is now the Kavli Nanoscience Institute, a nanotechnology fabrication center open to campus and JPL users, and he played an important role in LIGO, the Laser Interferometer Gravitational-wave Observatory.  

Tombrello co-advised many students with nanotechnologist Axel Scherer, the Bernard A. Neches Professor of Electrical Engineering, Applied Physics, and Physics. "Tom was deeply immersed in the work of my group—nanoscale vacuum tubes, new gene-sequencing systems, sensors for oilfield applications, and lithography at the atomic scale," Scherer says. "He had an intuitive understanding of the physics behind the devices."

A self-proclaimed "kindergarten dropout," Tombrello's true calling was teaching. "One of his most important legacies at Caltech was the creation of Physics 11 [in 1989], a freshman physics course that challenged incoming students to think in nonconventional ways," Koonin says. Applicants to the class completed assignments called "hurdles"—questions that had no right answers and generally had little to do with physics. "He wanted to know whether you had the creativity and courage to attack a strange new problem, work on it until you had a solution you believed in, and allow your solution to be judged on its merits," says Phys 11 veteran Charles Tschirhart, class of 2015.

Tombrello recruited faculty mentors for the students admitted to Physics 11; together, the group planned a summer research project for each student. Says Tschirhart, "The class was about as informal as a class can be; we talked about our work while lounging on a circle of beat-up couches around a whiteboard outside Professor Tombrello's office. The professors would sit among us on the couches while we talked. Conversations often strayed to science policy, history, school politics, and general advice for success in science and in life. It was probably the best thing that anyone could have done for my development as a scientist and as a person."

"He was a very kind person to be around," says senior Adam Jermyn. "He understood the undergraduates in a way I think is uncommon among the faculty. He came to our formal dinners, he talked to us outside of class, and he kept his finger on the pulse of student government. When I applied for permission to overload, he said it would make me miserable. However, he let me try it. I was miserable, and I learned a lesson I think he knew I would not have learned if he'd opposed me directly."

"Tom Tombrello was one of Caltech's most dedicated and effective servants," says former Caltech astrophysicist Marc Kamionkowski. "He could be brash, opinionated, and hot-tempered, but he was a deeply devoted and extraordinarily effective PMA chairman. He was not just dutiful and responsible, he was passionate. He believed with every ounce of his being that Caltech was a special place, that its students and faculty were extraordinary, and that it was his mission to do whatever he could to help them out. He worked tirelessly recruiting outstanding faculty and raising money for them while reserving time each week to work with the undergraduates he adored. With his Texas drawl and his frequent references—with a wink of an eye—to his Sicilian origins, he was one of a kind."

"Tom was an ensemble of talents not easily found in one person—a cross between Socrates, Leonardo Da Vinci and Abraham Lincoln," says high-energy physicist Maria Spiropulu, the last faculty member hired while Tombrello was division chair

"For half a century, Tom Tombrello has represented not just the DNA but the heart and soul of Caltech," says author, radio host, and performer Sandra Tsing Loh (BS '83), a Caltech Distinguished Alumna and a Tombrello protégé. "His legacy is legendary. His loss leaves a giant meteorite crater. If heaven has an Ath, Dr. T. is being welcomed to his much-deserved corner table, although we'll sorely miss him from down here."

Tombrello received two teaching awards from the Associated Students of the California Institute of Technology (ASCIT), and, in 1994, the first Richard P. Feynman Prize for Excellence in Teaching, in part for the creation of Physics 11. He was named the William R. Kenan, Jr. Professor of Physics in 1997, and Robert H. Goddard Professor of Physics in 2012. He was also a fellow of the American Physical Society; a member of Sigma Xi, the international honorary society for science and engineering; and of Phi Beta Kappa, the nation's oldest academic honor society.

Tombrello is survived by his second wife, Stephanie; his first wife, Ann, and their children, Christopher Tombrello, Susan Tombrello, and Karen Burgess; and seven grandchildren. He was predeceased by his stepdaughter, Kerstin.

Memorial donations may be made to the Thomas Tombrello Physics 11 Scholarship Fund by clicking on the link to the fund under his picture, selecting "special gifts," scroll downing and checking "other," and writing "Thomas Tombrello Physics 11 Scholarship" in the "Comments" box. 

Plans for a memorial service are pending.

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Douglas Smith
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Quantum States of Matter in Crystals

Watson Lecture Preview

David Hsieh, an assistant professor of physics at Caltech, is searching for new forms of matter that exhibit weird quantum properties in bulk. Find out the why, where, and how at 8 p.m. on Wednesday, October 15, in Caltech's Beckman Auditorium. Admission is free.

 

Q: What do you do?

A: I'm an experimental condensed-matter physicist. I'm searching for quantum phases of matter in crystals big enough to hold in your hand. A quantum phase occurs when the electrons in a crystal share a quantum state that creates an interdependence among them. This can lead to tangible phenomena that seem to defy the laws of everyday physics.  

The three familiar phases of matter—solids, liquids, gases—are governed by electrostatic forces. Likewise, free electrons interact with one another through electrostatic repulsions. If you just threw a bunch of electrons into a box, they'd eventually situate themselves as far away from one another as possible. These forces are not under our control, but when we embed electrons in a crystal, they swim in a lattice of ions that can facilitate many other types of interactions. By properly choosing those ions, we can actually exert a significant degree of control over the interactions and start creating new forms of quantum matter. My group is particularly interested in two types of interactions: electron-electron repulsion, and spin-orbit coupling.

Electron-electron repulsions are relatively weak in the metals we typically encounter in daily life. But under the right circumstances, the repulsions can get really, really big, and the material becomes a high-temperature superconductor. "High temperature" in this context means keeping the material at –135°C instead of –245°C, or in other words, keeping them really cold as opposed to really, really cold. Can a room-temperature superconductor be made? Nobody knows.

The other interaction that interests me is called spin-orbit coupling. Basically, an electron can be either "spin up" or "spin down," and most materials have an equal population of each all swimming around in random directions through the crystal. An atomic nucleus has a positive charge, so it emits an electric field. If the atom is really big and heavy, like lead or bismuth, the field is actually strong enough to torque the spins of passing electrons so that they all leave pointing in the same direction. The importance of spin-orbit coupling was given a huge boost about 10 years ago, when people began to think about so-called "topological order" in crystals. The hallmark of topological objects is that the bulk of that object doesn't carry electricity, but the boundaries carry it almost perfectly. This property cannot be induced in a non-topological system.

 

Q: What are these quantum phases of matter good for?

A: If you have something that carries electricity almost perfectly, the most straightforward application is microelectronic circuitry. Integrated circuits are made of semiconductors; the electricity that a semiconductor does not conduct gets dissipated as heat, which is why computer rooms are so heavily air-conditioned. A near-perfect conductor would generate very little heat. It could be a very "green" technology, so if you're running huge server farms, like Amazon.com or Google, the energy savings would be tremendous.

Moreover, the current would be spin-polarized—all the electrons' spins would point in the same direction—making topological materials ideal for wiring up spintronic circuits. Spintronics is an emerging computer technology that reads and writes information by using electric fields to manipulate spins, or magnetic fields to manipulate charge.

And if you start to assemble structures from both topological and conventional materials, you may get objects that might be used to build quantum computers.

I'd like to push further. Nobody knows what happens when you create both spin-orbit interactions and electron-electron interactions in the same crystal. A lot of condensed-matter physicists are going in that direction—it's an experimentally unknown territory.

We're also looking for what are called topological superconductors. Topological superconductors are predicted to have the potential to perform quantum computations in a fault-tolerant way, meaning that they would resist perturbations from the outside world that would otherwise crash the computer. There's a huge quantum-computing effort going on at Caltech, and engineering fault tolerance into the system is a key element.

 

Q: How did you get into this line of work?

A: Well, I wanted to do fundamental physics, but I also hoped to see societal benefits from my research within my lifetime. So I'm idealistic, but there's some pragmatism there, too. When I went to Princeton as a graduate student, I wanted to do experimental tests of string theory. But after a couple of years I grew increasingly attracted to condensed-matter physics, so I changed fields and wound up doing my PhD thesis on topological materials.

 

Named for the late Caltech professor Earnest C. Watson, who founded the series in 1922, the Watson Lectures present Caltech and JPL researchers describing their work to the public. Many past Watson Lectures are available online at Caltech's iTunes U site.

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Douglas Smith
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Watson Lecture: Quantum States of Matter in Crystals
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Friday, October 17, 2014
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TA Training: fall make-up session

Remembering Gerry Neugebauer

1932–2014

Gerry Neugebauer, Caltech's Robert Andrews Millikan Professor of Physics, Emeritus, passed away on September 26, 2014, of complications from spinocerebellar ataxia, a neurodegenerative disease. He was 82. 

Neugebauer was one of the founders of the field of infrared astronomy, the study of astronomical objects using the heat energy they emit.

"Gerry's foundational contributions to infrared astronomy laid the groundwork for the more than $10 billion in investments in this discipline that many countries have made in their infrared space projects, as well as substantial components of ground-based telescopes," says Tom Soifer (BS '68), professor of physics, Kent and Joyce Kresa Leadership Chair of the Division of Physics, Mathematics and Astronomy (PMA) at Caltech, and Neugebauer's protégé and longtime collaborator. "None of this would have happened without the excitement of the discoveries made by Gerry and his students and colleagues."

"During his career, Gerry had a profound impact on JPL and Caltech," says Charles Elachi (MS '69, PhD '71), JPL's director and a professor of electrical engineering and planetary science at Caltech. "He truly was the father of infrared space astronomy."

Neugebauer was born on September 3, 1932, in Göttingen, Germany, to Grete Bruck and Otto Neugebauer, a noted mathematical historian. The family soon relocated to Copenhagen and then to Providence, Rhode Island, in 1939, after Otto took a faculty position at Brown University. The younger Neugebauer earned an AB in physics from Cornell University in 1954 and his PhD in physics from Caltech in 1960, after which he served two years in the United States Army, stationed at JPL. There, he was assigned to work on the infrared instrument on the Mariner 2 space probe, which, upon its arrival at Venus in 1962, became the first successful NASA mission to another planet. 

In 1962, Neugebauer returned to Caltech as an assistant professor of physics and began working with astrophysicist Bob Leighton on the world's first infrared sky survey, the Two-Micron Sky Survey (TMSS). The survey revealed an unexpectedly large number of relatively cool objects, including new stars still surrounded by their dusty pre-stellar shells and supergiant stars in the last stages of their evolution. "This work was a huge milestone in astronomy," Soifer says, "in that it demonstrated that the infrared portion of the electromagnetic spectrum held tremendous excitement and potential for discovery in astronomy."

Neugebauer later led the science team for the first orbiting infrared observatory, the Infrared Astronomical Satellite (IRAS), which conducted the first far-infrared sky survey and eventually detected more than half a million sources of infrared radiation, including numerous galaxies and the debris rings around stars that gave astronomers early hints of the existence of extrasolar planets. He and his colleagues obtained the first infrared view of the galactic center, and he was the codiscoverer, with astrophysicist Eric Becklin (PhD '68) of the Becklin-Neugebauer Object, a massive but compact and intensely bright newly forming star in the Orion Nebula, previously undetected at other wavelengths of light.

"Gerry had original, expansive ideas about how to illuminate the relatively unknown infrared universe," adds France Córdova (PhD '79), the director of the National Science Foundation. "He became one of the first to work with X-ray astronomers to identity mysterious astrophysical sources and encouraged students in both infrared and X-ray fields to work and learn together."

As the chair of the Division of Physics, Mathematics and Astronomy, a position he held from 1988 to 1993, Neugebauer played a key role in the design and construction of the W. M. Keck Observatory in Hawaii, and he participated in the first science run of the first instrument on the Keck 1 telescope, the Near Infrared Camera. From 1980 to 1994, he also served as the director of the Palomar Observatory and spearheaded significant upgrades to the observatory's telescopes.

In addition to his scientific and administrative achievements, Neugebauer was a dedicated educator and mentor. "Gerry was devoted to Caltech, and he was an outstanding teacher," Soifer says. "He participated as one of the junior faculty with the group surrounding Richard Feynman as Feynman did the lectures on physics that are the benchmark of learning physics for all practicing physicists." 

"He had the marvelous capability to sense when you were in trouble on something, and promptly showed up to help," recalls Robbie Vogt, R. Stanton Avery Distinguished Service Professor and Professor of Physics, Emeritus, and a former Caltech provost and PMA division chair, who had an adjoining office with Neugebauer when both joined the Caltech faculty as young assistant professors, and who worked with him on the Feynman lectures.

"Whether he was at the telescope or in the instrument lab, he was hands-on and treated his students like peers," Córdova says. "He was an active listener with helpful advice about the range of a student's concerns. He was always himself and always looked happy, even when he definitely was not, because he loved what he was doing and cared about the people with whom he worked."

"He was a mentor and colleague with great integrity, who got the best out of all who worked with him," adds Becklin, professor of physics and astronomy, emeritus, at the University of California, Los Angeles.

"Gerry was the chair of PMA at Caltech during five years while I was president. The personal sensitivity that his students describe, he extended to all members of his division during his chairmanship," says Thomas E. Everhart, president emeritus and professor of electrical engineering and applied physics, emeritus. "He was an excellent representative in the Institute Academic Committee, explaining the science in his division to the other chairs, the provost, and me, and he was instrumental in establishing the leadership of the LIGO [Laser Interferometer Gravitational-wave Observatory] project on campus after the award from the National Science Foundation, as well as overseeing many other projects in PMA. He was not only a great scientist but also answered the call of his division to provide it leadership. He has been greatly missed since disease shortened his spectacular career at Caltech."

"Simply put, he was one of the greatest scientists and human beings I know, and I will forever be grateful for having had the opportunity to work with him," says Andrea Ghez (MS '89, PhD '93) of the University of California, Los Angeles, an advisee of Neugebauer's and the discoverer of a supermassive black hole at the center of our galaxy.

"He was the best mentor one could possibly hope for," she says. "I learned from him what it means to be a scientist: how to ask good scientific questions, how to design an experiment that can actually answer the question you've asked, the importance of a completely rigorous analysis and communicating clearly what you have done. He held himself and everyone around him to incredibly high standards and was absolutely devoted to the pure pursuit of science. He was not only a great scientist who was so willing to do the things that were uncharted, but he was also a tremendous human being who cared deeply for those around him. His influence was, and will continue to be, immense, both in the field of astronomy and on those of us fortunate enough to work with him.

"Gerry was a magnificent mentor and teacher," adds Soifer. "He inspired, pushed, taught how to do science with integrity and have fun. He never expected more from his students than he did of himself. For me, he was an inspiration, from when I worked on the two-micron survey as an undergraduate, to collaborating with him in many scientific endeavors, to watching him handle the intractable problems of guiding the IRAS science team through many trials and tribulations both technical and political, to watching him guide Palomar and the division, to watching him handle with grace the debilitating condition that he suffered from for the last two decades of his life. He was a wonderful counselor and valued friend."

Neugebauer was a member of the National Academy of Sciences, the American Philosophical Society, and the American Academy of Arts and Sciences and was a fellow of the Royal Astronomical Society. His numerous prizes included the Rumford Prize of the American Academy of Arts and Sciences (1986), the Herschel Medal of the Royal Astronomical Society (1998), the Space Science Award of the American Institute of Aeronautics and Astronautics (1985), two NASA Exceptional Scientific Achievement awards (1972 and 1984), and lifetime achievement awards from the American Astronomical Society (the Henry Norris Russell Lectureship, 1996) and the Astronomical Society of the Pacific (the Catherine Wolfe Bruce Medal, 2010). He was named California Scientist of the Year in 1986.

He is survived by his wife, Marcia Neugebauer, a geophysicist at JPL; daughters Carol Kaplan and Lee Neugebauer; and two granddaughters.

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Kathy Svitil
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Alumnus Eric Betzig Wins 2014 Nobel Prize in Chemistry

Eric Betzig (BS '83), a group leader at the Howard Hughes Medical Institute's Janelia Farm Research Campus in Ashburn, Virginia, has been awarded the 2014 Nobel Prize in Chemistry along with Stefan W. Hell of the Max Planck Institute for Biophysical Chemistry and William E. Moerner of Stanford University. The three were honored "for the development of super-resolved fluorescence microscopy," a method that allows for the creation of "super-images" with a resolution on the order of nanometers, or billionths of a meter. In essence, the work turns microscopy into "nanoscopy."

The technique developed by the trio overcomes the so-called Abbe diffraction limit, which describes a physical restriction on the sizes of the structures that can be resolved using optical microscopy, showing that, essentially, nothing smaller than one-half the wavelength of light, or about 0.2 microns, can be discerned by these scopes. The result of the Abbe limit is that only the larger structures within cells—organelles like mitochondria, for example—can be resolved and studied with regular microscopes but not individual proteins or even viruses. The restriction is akin to being able to observe the buildings that make up a city but not the city's inhabitants and their activities.

Betzig, building on earlier work by Hell and Moerner, found that it was possible to work around the Abbe limit to create very-high-resolution images of a sample, such as a developing embryo, by using fluorescent proteins that glow when illuminated with a weak pulse of light. Each time the sample is illuminated, a different, sparsely distributed subpopulation of fluorescent proteins will light up and, because the glowing molecules are spaced farther apart than the Abbe diffraction limit, a standard microscope would be able to capture them. Still, each of the images produced in this way has relatively low resolution—that is, they are blurry. Betzig, however realized that by superimposing many such images, he would be able to obtain a sharp super-image, in which nanoscale structures are clearly visible. The new technique was first described in a 2006 paper published in the journal Science.

After Caltech, Betzig, a physics major from Ruddock House, earned an MS (1985) and a PhD (1988) from Cornell University. He worked at AT&T Bell Laboratories until 1994, when he stepped away from academia and science to work for his father's machine tool company. Betzig returned to research in 2002 and joined Janelia in 2005.

To date, 33 Caltech alumni and faculty have won a total of 34 Nobel Prizes. Last year, alumnus Martin Karplus (PhD '54) also received the Chemistry Prize. 

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Kathy Svitil
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Caltech Physics Professors Earn NASA Medals

James J. (Jamie) Bock, professor of physics at Caltech and a senior research scientist at JPL, and Caltech Professor of Physics Christopher Martin were among those receiving NASA Honor Awards from JPL director Charles Elachi (MS '69, PhD '71) and John Grunsfeld, NASA's associate administrator for the Science Mission Directorate, in a ceremony on Tuesday, September 16.

Bock was awarded NASA's Distinguished Service Medal for "accomplishments in cosmology including development and application of new detector technology leading to advances in our knowledge of the Universe."

Martin, the principal investigator for the Galaxy Evolution Explorer, an Earth-orbiting space telescope that studies the universe in ultraviolet light, was given the NASA Exceptional Scientific Achievement Medal, awarded for efforts resulting in key scientific discoveries or contributions of fundamental importance to the field in question, including, according to the award citation, "the new understanding of galaxy evolution, the identification of new environments for star formation, and an invaluable data archive of UV images of most of the sky."

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NuSTAR Discovers Impossibly Bright Dead Star

X-ray source in the Cigar Galaxy is the first ultraluminous pulsar ever detected

Astronomers working with NASA's Nuclear Spectroscopic Telescope Array (NuSTAR), led by Caltech's Fiona Harrison, have found a pulsating dead star beaming with the energy of about 10 million suns. The object, previously thought to be a black hole because it is so powerful, is in fact a pulsar—the incredibly dense rotating remains of a star.

"This compact little stellar remnant is a real powerhouse. We've never seen anything quite like it," says Harrison, NuSTAR's principal investigator and the Benjamin M. Rosen Professor of Physics at Caltech. "We all thought an object with that much energy had to be a black hole."

Dom Walton, a postdoctoral scholar at Caltech who works with NuSTAR data, says that with its extreme energy, this pulsar takes the top prize in the weirdness category. Pulsars are typically between one and two times the mass of the sun. This new pulsar presumably falls in that same range but shines about 100 times brighter than theory suggests something of its mass should be able to.

"We've never seen a pulsar even close to being this bright," Walton says. "Honestly, we don't know how this happens, and theorists will be chewing on it for a long time." Besides being weird, the finding will help scientists better understand a class of very bright X-ray sources, called ultraluminous X-ray sources (ULXs).

Harrison, Walton, and their colleagues describe NuSTAR's detection of this first ultraluminous pulsar in a paper that appears in the current issue of Nature.

"This was certainly an unexpected discovery," says Harrison. "In fact, we were looking for something else entirely when we found this."

Earlier this year, astronomers in London detected a spectacular, once-in-a-century supernova (dubbed SN2014J) in a relatively nearby galaxy known as Messier 82 (M82), or the Cigar Galaxy, 12 million light-years away. Because of the rarity of that event, telescopes around the world and in space adjusted their gaze to study the aftermath of the explosion in detail.


This animation shows a neutron star—the core of a star that exploded in a massive supernova. This particular neutron star is known as a pulsar because it sends out rotating beams of X-rays that sweep past Earth like lighthouse beacons. (Credit: NASA/JPL-Caltech)

Besides the supernova, M82 harbors a number of other ULXs. When Matteo Bachetti of the Université de Toulouse in France, the lead author of this new paper, took a closer look at these ULXs in NuSTAR's data, he discovered that something in the galaxy was pulsing, or flashing light.

"That was a big surprise," Harrison says. "For decades everybody has thought these ultraluminous X-ray sources had to be black holes. But black holes don't have a way to create this pulsing."

But pulsars do. They are like giant magnets that emit radiation from their magnetic poles. As they rotate, an outside observer with an X-ray telescope, situated at the right angle, would see flashes of powerful light as the beam swept periodically across the observer's field of view, like a lighthouse beacon.

The reason most astronomers had assumed black holes were powering ULXs is that these X-ray sources are so incredibly bright. Black holes can be anywhere from 10 to billions of times the mass of the sun, making their gravitational tug much stronger than that of a pulsar. As matter falls onto the black hole the gravitational energy turns it to heat, which creates X-ray light. The bigger the black hole, the more energy there is to make the object shine.

Surprised to see the flashes coming from M82, the NuSTAR team checked and rechecked the data. The flashes were really there, with a pulse showing up every 1.37 seconds.

The next step was to figure out which X-ray source was producing the flashes. Walton and several other Caltech researchers analyzed the data from NuSTAR and a second NASA X-ray telescope, Chandra, to rule out about 25 different X-ray sources, finally settling on a ULX known as M82X-2 as the source of the flashes.

With the pulsar and its location within M82 identified, there are still many questions left to answer. It is many times higher than the Eddington limit, a basic physics guideline that sets an upper limit on the brightness that an object of a given mass should be able to achieve.

"This is the most extreme violation of that limit that we've ever seen," says Walton. "We have known that things can go above that by a small amount, but this blows that limit away."

NuSTAR is particularly well-suited to make discoveries like this one. Not only does the space telescope see high-energy X-rays, but it sees them in a unique way. Rather than snapping images the way that your cell-phone camera does—by integrating the light such that images blur if you move—NuSTAR detects individual particles of X-ray light and marks when they are measured. That allows the team to do timing analyses and, in this case, to see that the light from the ULX was coming in pulses.

Now that the NuSTAR team has shown that this ULX is a pulsar, Harrison points out that many other known ULXs may in fact be pulsars as well. "Everybody had assumed all of these sources were black holes," she says. "Now I think people have to go back to the drawing board and decide whether that's really true. This could just be a very unique, strange object, or it could be that they're not that uncommon. We just don't know. We need more observations to see if other ULXs are pulsing."

Along with Harrison and Walton, additional Caltech authors on the paper, "An Ultraluminous X-ray Source Powered by An Accreting Neutron Star," are postdoctoral scholars Felix Fürst, and Shriharsh Tendulkar; research scientists Brian W. Grefenstette and Vikram Rana; and Shri Kulkarni, the John D. and Catherine T. MacArthur Professor of Astronomy and Planetary Science and director of the Caltech Optical Observatories. The work was supported by NASA and made use of data supplied by the UK Swift Science Data Centre at the University of Leicester.

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Kimm Fesenmaier
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TMT Breaks Ground

Today at 3 p.m. PDT, a groundbreaking and blessing ceremony approximately 14,000 feet above sea level, near the summit of Hawaii's Mauna Kea, will officially kick off construction for the next-generation Thirty Meter Telescope (TMT).

The ceremony, preceded by pre-recorded science segments, can be viewed live beginning at 2:15 p.m. PDT. Log on to TMT.org/buildingTMT to watch the groundbreaking ceremonies. Viewers worldwide are welcome to send greetings to TMT (@TMTHawaii) via the hashtag #buildingTMT.

Henry Yang, chair of the TMT International Observatory (TIO) board and chancellor of the University of California, Santa Barbara, will deliver the groundbreaking program's opening remarks, followed by Hawaii Governor Neil Abercrombie and Hawaii County Mayor William Kenoi. The program will conclude with a traditional Hawaiian ceremony that will include Caltech President Thomas F. Rosenbaum. Also in attendance will be Provost Edward Stolper; Board of Trustees Chair David Lee (PhD, '74); Senior Trustee Walter L. Weisman and Life Trustee Gordon Moore (PhD, '54); Tom Soifer (BS, '68), Kent and Joyce Kresa Leadership Chair of the Division of Physics, Mathematics and Astronomy; Ed Stone, the David Morrisroe Professor of Physics and TIO executive director; and other members of the Caltech administration and faculty.

When completed, TMT will be the world's most advanced optical/near-infrared observatory, offering the highest-definition views ever achieved of planets orbiting nearby stars and the first stars and galaxies in the distant universe, and enabling researchers to tackle some of humanity's most fundamental and elusive questions.

Caltech, in collaboration with the University of California and scientists from Japan, China, India, and Canada, and with generous financial support from the Gordon and Betty Moore Foundation, spearheaded the design and construction of the $1.4 billion project, which was first conceived more than a decade ago.

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TMT Groundbreaking Launches New Era of Discovery

Construction officially has begun near the summit of Hawaii's Mauna Kea on what will be the largest telescope on the planet: the Thirty Meter Telescope (TMT).

"It is both exhilarating and intimidating to have reached this point," says Tom Soifer, professor of physics and Kent and Joyce Kresa Leadership Chair of the Division of Physics, Mathematics and Astronomy at Caltech. "It is exhilarating because of the enormous amount of effort it has taken us to get here and because, now that we are at the groundbreaking, TMT—and the scientific opportunities it brings—becomes much more real. It is intimidating because we've only just begun the work."

TMT, which is scheduled to begin observations in the early 2020s, will join the family of observatories already on Mauna Kea, including Caltech's twin 10-meter telescopes at the W. M. Keck Observatory, the current record-holder for the largest optical and infrared telescope in the world.

At 10 to 100 times more sensitive than Keck—depending on the type of observation—TMT is designed to tackle the most challenging questions of the cosmos, such as whether there is life on planets beyond the solar system, the nature of dark energy and dark matter, and the formation and evolution of galaxies.

Wide-angle view of 200-inch Hale Telescope
Credit: Scott Kardel

Caltech has played a leading role in the conception, design, and construction of the TMT, the latest (and greatest) of the Institute's pioneering efforts to build the most powerful observatories in the world. In the early 20th century, astronomer George Ellery Hale, one of the founders of Caltech, spearheaded the construction of the 200-inch telescope at Palomar Observatory, which stood as the largest telescope for 45 years until 1993 when Caltech and the University of California built the W. M. Keck Observatory. The Hale Telescope, as it became known, helped astronomers measure the expansion of the universe and discover exotic, bright objects called quasars, among numerous other achievements.

The twin 10-meter Keck telescope domes on Mauna Kea, Hawaii
Credit: Rick Peterson/WMKO

Caltech was also instrumental in the design and construction of Keck, which has become the preeminent optical and infrared observatory in the world. Over the last two decades, astronomers from around the globe—including many at Caltech—have used the twin Keck telescopes to detect planets beyond the solar system and peer into other planetary systems; probe the black hole at the center of the Milky Way galaxy; learn how the universe has evolved since the Big Bang, how galaxies form, and how stars are born; and to study dark matter, the mysterious stuff that makes up most of the universe's mass, and dark energy, the enigmatic force that's expanding the universe at an ever-faster rate.

The design of TMT and its instruments are based on Keck—only bigger, faster, and better. For example, each Keck telescope comprises 36 hexagonal mirror segments, which together act as a 10-meter-wide mirror. TMT, on the other hand, will have 492 segments that function as a 30-meter-wide mirror.

With such light-gathering ability, state-of-the-art instruments, and a first-ever fully integrated adaptive optics system to cancel out the blurring effects of the atmosphere, TMT will be able to see farther and more clearly than Keck or any other telescope at the same optical and infrared wavelengths.

For example, it will capture unprecedented images of planets beyond our solar system, revealing their atmospheres and environments in detail, and bring astronomers closer to answering the question of whether there is life elsewhere in the universe.

TMT will study how galaxies form and evolve, and how they're distributed across the universe. By exploring the large-scale structure of the universe and how it has changed over time, astronomers can probe dark energy and dark matter, as-yet invisible stuff that seems to interact only gravitationally with ordinary matter like stars. Both comprise the vast majority of the matter and energy in the universe and remain one of the most confounding questions in science.

The telescope will peer back in time to observe the first galaxies that came into existence 13 billion years ago, unveiling an era of cosmic history just beyond the reach of current telescopes.

TMT will study black holes that are millions to billions of times as massive as the sun and reside at the center of distant galaxies. It will also examine enormous explosions known as gamma-ray bursts, which are the most powerful events in the universe.

But what has many astronomers the most excited is not the expected discoveries, but the surprises that await, says Ed Stone, Caltech's David Morrisroe Professor of Physics and executive director of the TMT International Observatory, an international partnership that includes Caltech, the National Astronomical Observatories of the Chinese Academy of Sciences, the National Institutes of Natural Sciences in Japan, and the University of California. "It's not just about understanding better what you already know but learning what you didn't even know was out there," he says.

These future discoveries, Soifer adds, would not be possible were it not for the vision and continuing support of Caltech's collaborators and partners. "Gordon and Betty Moore and the Moore Foundation have been essential to getting TMT where we are today," Soifer says. That support began with a gift of $140 million to Caltech and the University of California to develop the early concept of a telescope larger than Keck. "The foundation has continued to provide the critical support that has allowed the project to continue," he says. "TMT is a testament to the Moore Foundation, our ingenuity, and the spirit of exploration."

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