The Planet Finder: A Conversation with Dimitri Mawet

Associate Professor of Astronomy Dimitri Mawet has joined Caltech from the Paranal Observatory in Chile, where he was a staff astronomer for the Very Large Telescope. After earning his PhD at the University of Liège, Belgium, in 2006, he was at JPL from 2007 to 2011—first as a NASA postdoctoral scholar and then as a research scientist.

 

Q: What do you do?

A: I study exoplanets, which are planets orbiting other stars. In particular, I'm developing technologies to view exoplanets directly and analyze their atmospheres. We're hunting for small, Earth-like planets where life might exist—in other words, planets that get just the right amount of heat to maintain water in its liquid state—but we're not there yet. For an exoplanet to be imaged right now, it has to be really big and really bright, which means it's very hot.

In order to be seen in the glare of its star, the planet has to be beyond a minimum angular separation called the inner working angle. Separations can also be expressed in astronomical units, or AUs, where one AU is the mean distance between the sun and Earth. Right now we can get down to about two AU—but only for giant planets. For example, we recently imaged Beta Pictoris and HR 8799. We didn't find anything at two AU in either star system, but we found that Beta Pictoris harbors a planet about eight times more massive than Jupiter orbiting at 9 AU. And we see a family of four planets in the five- to seven-Jupiters range that orbit from 14 to 68 AU around HR 8799. For comparison, Saturn is 9.5 AU from the sun, and Neptune is 30 AU.

 

Q: How can we narrow the working angle?

A: You either build an interferometer, which blends the light from two or more telescopes and "nulls out" the star, or you build a coronagraph, which blots out the star's light. Most coronagraphs block the star's image by putting a physical mask in the optical path. The laws of physics say their inner working angles can't be less than the so-called diffraction limit, and most coronagraphs work at three to five times that. However, when I was a grad student, I invented a coronagraph that works at the diffraction limit.

The key is that we don't use a physical mask. Instead, we create an "optical vortex" that expels the star's light from the instrument. Some of our vortex masks are made from liquid-crystal polymers, similar to your smartphone's display, except that the molecules are "frozen" into orientations that force light waves passing through the center of the mask to emerge in different phase states simultaneously. This is not something nature allows, so the light's energy is nulled out, creating a "dark hole."

If we point the telescope so the star's image lands exactly on the vortex, its light will be filtered out, but any light that's not perfectly centered on the vortex—such as light from the planets, or from a dust disk around the star—will be slightly off-axis and will go on through to the detector.

We're also pushing to overcome the enormous contrast ratio between the very bright star and the much dimmer planet. Getting down to the Earth-like regime requires a contrast ratio of 10 billion to 1, which is really huge. The best contrast ratios achieved on ground-based telescopes today are more like 1,000,000 to 1. So we need to pump it up by another factor of 10,000.

Even so, we can do a lot of comparative exoplanetology, studying any and all kinds of planets in as many star systems as we can. The variety of objects around other stars—and within our own solar system—is mind-boggling. We are discovering totally unexpected things.

 

Q: Such as?

A: Twenty years ago, people were surprised to discover hot Jupiters, which are huge, gaseous planets that orbit extremely close to their stars—as close as 0.04 AU, or one-tenth the distance between the sun and Mercury. We have nothing like them in our solar system. They were discovered indirectly, by the wobble they imparted to their star or the dimming of their star's light as the planet passed across the line of sight. But now, with high-contrast imaging, we can actually see—directly—systems of equally massive planets that orbit tens or even hundreds of AU's away from their stars, which is baffling.

Planets form within circumstellar disks of dust and gas, but these disks get very tenuous as you go farther from the star. So how did these planets form? One hypothesis is that they formed where we see them, and thus represent failed attempts to become multiple star systems. Another hypothesis is that they formed close to the star, where the disk is more massive, and eventually expelled one another by gravitational interactions.

We're trying to answer that question by starting at the outskirts of these planetary systems, looking for massive, hot planets in the early stages of formation, and then grind our way into the inner reaches of older planetary systems as we learn to reduce the working angle and deal with ever more daunting contrast ratios. Eventually, we will be able to trace the complete history of planetary formation.

 

Q: How can you figure out the history?

Once we see the planet, once we have its signal in our hands, so to speak, we can do all kinds of very cool measurements. We can measure its position, that's called astrometry; we can measure its brightness, which is photometry; and, if we have enough signal, we can sort the light into its wavelengths and do spectroscopy.

As you repeat the astrometry measurements over time, you resolve the planet's orbit by following its motion around its star. You can work out masses, calculate the system's stability. If you add the time axis to spectrophotometry, you can begin to track atmospheric features and measure the planet's rotation, which is even more amazing.

Soon we'll be able to do what we call Doppler imaging, which will allow us to actually map the surface of the planet. We'll be able to resolve planetary weather phenomena. That's already been done for brown dwarfs, which are easier to observe than exoplanets. The next generation of adaptive optics on really big telescopes like the Thirty Meter Telescope should get us down to planetary-mass objects.

That's why I'm so excited about high-contrast imaging, even though it's so very, very hard to do. Most of what we know about exoplanets has been inferred. Direct imaging will tell us so much more about exoplanets—what they are made out of and how they form, evolve, and interact with their surroundings.

 

Q: Growing up, did you always want to be an astronomer?

A: No. I wanted to get into space sciences—rockets, satellite testing, things like that. I grew up in Belgium and studied engineering at the University of Liège, which runs the European Space Agency's biggest testing facility, the Space Center of Liège. I had planned to do my master's thesis there, but there were no openings the year I got my diploma.

I was not considering a thesis in astronomy, but I nevertheless went back to campus, to the astrophysics department. I knew some of the professors because I had taken courses with them. One of them, Jean Surdej, suggested that I work on a concept called the Four-Quadrant Phase-Mask (FQPM) coronagraph, which had been invented by French astronomer Daniel Rouan. I had been a bit hopeless, thinking I would not find a project I would like, but Surdej changed my life that day.

The FQPM was one of the first coronagraphs designed for very-small-working-angle imaging of extrasolar planets. These devices performed well in the lab, but had not yet been adapted for use on telescopes. Jean, and later on Daniel, asked me to help build two FQPMs—one for the "planet finder" on the European Southern Observatory's Very Large Telescope, or VLT, in Chile; and one for the Mid-Infrared Instrument that will fly on the James Webb Space Telescope, which is being built to replace the Hubble Space Telescope.

I spent many hours in Liège's Hololab, their holographic laboratory, playing with photoresists and lasers. It really forged my sense of what the technology could do. And along the way, I came up with the idea for the optical vortex.

Then I went to JPL as a NASA postdoc with Eugene Serabyn. I still spent my time in the lab, but now I was testing things in the High Contrast Imaging Testbed, which is the ultimate facility anywhere in the world for testing coronagraphs. It has a vacuum tank, six feet in diameter and eight feet long, and inside the tank is an optical table with a state-of-the-art deformable mirror. I got a few bruises crawling around in the tank setting up the vortex masks and installing and aligning the optics.

The first vortex coronagraph actually used on the night sky was the one we installed on the 200-inch Hale Telescope down at Palomar Observatory. The Hale's adaptive optics enabled us to image the planets around HR 8799, as well as brown dwarfs, circumstellar disks, and binary star systems. That was a fantastic and fun learning experience.

So I developed my physics and manufacturing intuition in Liège, my experimental and observational skills at JPL, and then I went to Paranal where I actually applied my research. I spent about 400 nights observing at the VLT; I installed two new vortex coronagraphs with my Liège collaborators; and I became the instrument scientist for SPHERE, to which I had contributed 10 years before when it was called the planet finder. And I learned how a major observatory operates—the ins and outs of scheduling, and all the vital jobs that are performed by huge teams of engineers. They far outnumber the astronomers, and nothing would function without them.

And now I am super excited to be here. Caltech and JPL have so many divisions and departments and satellites—like Caltech's Division of Physics, Mathematics and Astronomy and JPL's Science Division, both my new professional homes, but also Caltech's Division of Geology and Planetary Sciences, the NASA Exoplanet Science Institute, the Infrared Processing and Analysis Center, etc. We are well-connected to the University of California. There are so many bridges to build between all these places, and synergies to benefit from. This is really a central place for innovation. I think, for me, that this is definitely the center of the world.

Writer: 
Douglas Smith
Writer: 
Exclude from News Hub: 
No
Short Title: 
The Planet Finder
News Type: 
Research News

Scoville Awarded Radio Astronomy Lectureship

Nick Scoville, the Francis L. Moseley Professor of Astronomy, has been awarded the 2015 Karl G. Jansky Lectureship from the National Radio Astronomy Observatory (NRAO) and the Associated Universities, Inc. The lectureship is named for Karl Jansky, a pioneer in the field of radio astronomy and the first to detect radio waves from a cosmic source.

Scoville's research currently focuses on the formation and evolution of galaxies and their central black holes, as studied using the Cosmic Evolution Survey (COSMOS). The survey maps galaxies as a function of cosmic time by observing the redshift in their light spectra. Redshift is the physical phenomenon in which the light spectrum emitted by an object will be shifted toward longer, redder wavelengths, due to the object's movement away from an observer. Scoville is interested in mapping large-scale structures of the universe at high redshift—such structures would include superclusters of galaxies that form the "cosmic web." He is currently using the new Atacama Large Millimeter Array (ALMA) to investigate the evolution of star formation in the early Universe and colliding starburst galaxies nearby.

Scoville arrived at Caltech as a professor in 1984. He has previously been the director of Caltech's Owens Valley Radio Observatory, and his previous awards include a Guggenheim Fellowship, and the University of Arizona's Aaronson Lectureship, awarded for excellence in astronomical research. As Jansky Lecturer, Scoville will give public lectures at NRAO facilities in Charlottesville, Virginia; Green Bank, West Virginia; and Socorro, New Mexico.

Writer: 
Exclude from News Hub: 
No
News Type: 
In Our Community

Powerful New Radio Telescope Array Searches the Entire Sky 24/7

A new radio telescope array developed by a consortium led by Caltech and now operating at the Owens Valley Radio Observatory has the ability to image simultaneously the entire sky at radio wavelengths with unmatched speed, helping astronomers to search for objects and phenomena that pulse, flicker, flare, or explode.

The new tool, the Owens Valley Long Wavelength Array (OV-LWA), is already producing unprecedented videos of the radio sky. Astronomers hope that it will help them piece together a more complete picture of the early universe and learn about extrasolar space weather—the interaction between nearby stars and their orbiting planets.

The consortium includes astronomers from Caltech, JPL, Harvard University, the University of New Mexico, Virginia Tech, and the Naval Research Laboratory.

"Our new telescope lets us see the entire sky all at once, and we can image everything instantaneously," says Gregg Hallinan, an assistant professor of astronomy at Caltech and OV-LWA's principal investigator.

Combining the observing power of more than 250 antennas spread out over a desert area equivalent to about 450 football fields, the OV-LWA is uniquely sensitive to faint variable radio signals such as those produced by pulsars, solar flares, and auroras on distant planets. A single radio antenna would have to be a hundred meters wide to achieve the same sensitivity (the giant radio telescope at Arecibo Observatory in Puerto Rico is 305 meters in diameter). However, a telescope's field of view is governed by the size of its dish, and such an enormous instrument still would only see a tiny fraction of the entire sky.

"Our technique delivers the best of both worlds, offering good sensitivity and an enormous field of view," says Hallinan.

Operating at full speed, the new array produces 25 terabytes of data every day, making it one of the most data-intensive telescopes in the world. For comparative purposes, it would take more than 5,000 DVDs to store just one day's worth of the array's data. A supercomputer developed by a group led by Lincoln Greenhill of Harvard University for the NSF-funded Large-Aperture Experiment to Detect the Dark Ages (LEDA) delivers these data. It uses graphics processing units similar to those used in modern computer games to combine signals from all of the antennas in real time. These combined signals are then sent to a second computer cluster, the All-Sky Transient Monitor (ASTM) at Caltech and JPL, which produces all-sky images in real-time.

Hallinan says that the OV-LWA holds great promise for cosmological studies and may allow astronomers to watch the early universe as it evolved over time. Scientists might then be able to learn how and when the universe's first stars, galaxies, and black holes formed. But the formative period during which these events occurred is shrouded in a fog of hydrogen that is opaque to most radiation. Even the most powerful optical and infrared telescopes cannot peer through that fog. By observing the sky at radio frequencies, however, astronomers may be able to detect weak radio signals from the time of the births of those first stars and galaxies.

"The biggest challenge is that this weak radiation from the early universe is obscured by the radio emission from our own galaxy, which is about a million times brighter than the signal itself, so you have to have very carefully measured data to see it," says Hallinan. "That's one of the primary goals of our collaboration—to try to get the first statistical measure of that weak signal from our cosmic dawn."

If they are able to detect that signal, the researchers could be able to learn about the formation of the first stars and galaxies, their evolution, and how they eventually ionized the surrounding intergalactic medium, to give us the universe we observe today. "This new field offers the opportunity to see the universe evolve, in a cosmological movie of sorts," Hallinan says.

But Hallinan is most excited about using the array to study space weather in nearby stellar systems similar to our own. Our own sun occasionally releases bursts of magnetic energy from its atmosphere, shooting X-rays and other forms of radiation outward in large flares. Sometimes these flares are accompanied by shock waves called coronal mass ejections, which send particles and magnetic fields toward Earth and the other planets. Light displays, or auroras, are produced when those particles interact with atoms in a planet's atmosphere. These space weather events also occur on other stars, and Hallinan hopes to use the OV-LWA to study them.

"We want to detect coronal mass ejections on other stars with our array and then use other telescopes to image them," he says. "We're trying to learn about this kind of event on stars other than the sun and show that there are auroras caused by these events on planets outside our solar system."

The majority of stars in our local corner of the Milky Way are so-called M dwarfs, stars that are much smaller than our own sun and yet potentially more magnetically active. Thus far, surveys of exoplanets suggest that most such M dwarfs harbor small rocky planets. "That means it is very likely that the nearest habitable planet is orbiting an M dwarf," Hallinan says. "However, the possibility of a higher degree of activity, with extreme flaring and intense coronal mass ejections, may have an impact on the atmosphere of such a planet and affect habitability."

A coronal mass ejection from an M dwarf would shower charged particles on the atmosphere and magnetic field of an orbiting planet, potentially leading to aurorae and periodic radio bursts. Astronomers could determine the strength of the planet's magnetic field by measuring the intensity and duration of such an event. And since magnetic fields may protect planets from the activity of their host stars, many such measurements would shed light on the potential habitability of these planets.

For decades, astronomers have been trying to detect radio bursts associated with extrasolar space weather. This is challenging for two reasons. First, the radio emission pulses as the planet rotates, flashing like a lighthouse beacon, so astronomers have to be looking at just the right time to catch the flash. Second, the radio emission may brighten significantly as the velocity of a star's stellar wind increases during a coronal mass ejection.

"You need to be observing at that exact moment when the beacon is pointed in our direction and the star's stellar wind has picked up. You might need to monitor that planet for a decade to get that one event where it is really bright," Hallinan says. "So you need to be able to not just observe at random intervals but to monitor all these planets continuously. Our new array allows us to do that."

 The OV-LWA was initiated through the support of Deborah Castleman (MS '86) and Harold Rosen (MS '48; PhD '51)

Writer: 
Kimm Fesenmaier
Home Page Title: 
Imaging the Entire Radio Sky 24/7
Listing Title: 
Imaging the Entire Radio Sky 24/7
Writer: 
Exclude from News Hub: 
No
Short Title: 
Powerful New Radio Telescope Array
News Type: 
Research News
Monday, May 18, 2015
Brown Gymnasium – Scott Brown Gymnasium

Jupiter’s Grand Attack

Lopsided Star Explosion Holds the Key to Other Supernova Mysteries

New observations of a recently exploded star are confirming supercomputer model predictions made at Caltech that the deaths of stellar giants are lopsided affairs in which debris and the stars' cores hurtle off in opposite directions.

While observing the remnant of supernova (SN) 1987A, NASA's Nuclear Spectroscopic Telescope Array, or NuSTAR, recently detected the unique energy signature of titanium-44, a radioactive version of titanium that is produced during the early stages of a particular type of star explosion, called a Type II, or core-collapse supernova.

"Titanium-44 is unstable. When it decays and turns into calcium, it emits gamma rays at a specific energy, which NuSTAR can detect," says Fiona Harrison, the Benjamin M. Rosen Professor of Physics at Caltech, and NuSTAR's principal investigator.

By analyzing direction-dependent frequency changes—or Doppler shifts—of energy from titanium-44, Harrison and her team discovered that most of the material is moving away from NuSTAR. The finding, detailed in the May 8 issue of the journal Science, is the best proof yet that the mechanism that triggers Type II supernovae is inherently lopsided.

NuSTAR recently created detailed titanium-44 maps of another supernova remnant, called Cassiopeia A, and there too it found signs of an asymmetrical explosion, although the evidence in this case is not as definitive as with 1987A.

Supernova 1987A was first detected in 1987, when light from the explosion of a blue supergiant star located 168,000 light-years away reached Earth. SN 1987A was an important event for astronomers. Not only was it the closest supernova to be detected in hundreds of years, it marked the first time that neutrinos had been detected from an astronomical source other than our sun.

These nearly massless subatomic particles had been predicted to be produced in large quantities during Type II explosions, so their detection during 1987A supported some of the fundamental theories about the inner workings of supernovae.

With the latest NuSTAR observations, 1987A is once again proving to be a useful natural laboratory for studying the mysteries of stellar death. For many years, supercomputer simulations performed at Caltech and elsewhere predicted that the cores of pending Type II supernovae change shape just before exploding, transforming from a perfectly symmetric sphere into a wobbly mass made up of turbulent plumes of extremely hot gas. In fact, models that assumed a perfectly spherical core just fizzled out.

"If you make everything just spherical, the core doesn't explode. It turns out you need asymmetries to make the star explode," Harrison says.

According to the simulations, the shape change is driven by turbulence generated by neutrinos that are absorbed within the core. "This turbulence helps push out a powerful shock wave and launch the explosion," says Christian Ott, a professor of theoretical physics at Caltech who was not involved in the NuSTAR observations.

Ott's team uses supercomputers to run three-dimensional simulations of core-collapse supernovae. Each simulation generates hundreds of terabytes of results—for comparison, the entire print collection of the U.S. Library of Congress is equal to about 10 terabytes—but represents only a few tenths of a second during a supernova explosion.

A better understanding of the asymmetrical nature of Type II supernovae, Ott says, could help solve one of the biggest mysteries surrounding stellar deaths: why some supernovae collapse into neutron stars and others into a black hole to form a space-time singularity. It could be that the high degree of asymmetry in some supernovae produces a dual effect: the star explodes in one direction, while the remainder of the star continues to collapse in all other directions.

"In this way, an explosion could happen, but eventually leave behind a black hole and not a neutron star," Ott says.

The NuSTAR findings also increase the chances that Advanced LIGO—the upgraded version of the Laser Interferometer Gravitational-wave Observatory, which will begin to take data later this year—will be successful in detecting gravitational waves from supernovae. Gravitational waves are ripples that propagate through the fabric of space-time. According to theory, Type II supernovae should emit gravitational waves, but only if the explosions are asymmetrical.

Harrison and Ott have plans to combine the observational and theoretical studies of supernova that until now have been occurring along parallel tracks at Caltech, using the NuSTAR observations to refine supercomputer simulations of supernova explosions.

"The two of us are going to work together to try to get the models to more accurately predict what we're seeing in 1987A and Cassiopeia A," Harrison says.

Additional Caltech coauthors of the paper, entitled "44Ti gamma-ray emission lines from SN1987A reveal an asymmetric explosion," are Hiromasa Miyasaka, Brian Grefenstette, Kristin Madsen, Peter Mao, and Vikram Rana. The research was supported by funding from NASA, the French National Center for Space Studies (CNES), the Japan Society for the Promotion of Science, and the Technical University of Denmark.

This article also references the paper "Magnetorotational Core-collapse Supernovae in Three Dimensions," which appeared in the April 20, 2014, issue of Astrophysical Journal Letters.

Home Page Title: 
NuSTAR Observations Hold Key to Supernova Mysteries
Listing Title: 
NuSTAR Observations Hold Key to Supernova Mysteries
Writer: 
Exclude from News Hub: 
No
News Type: 
Research News

Searching for Vibrations from the Big Bang

Watson Lecture Preview

For a brief instant after the Big Bang, the universe went through a period of rapid expansion during which space itself was flung apart faster than the speed of light. This "inflationary epoch" sowed the gravitational seeds that formed galaxies and clusters of galaxies. Its echoes linger as fluctuations imprinted on the so-called cosmic microwave background radiation—the Big Bang's glow, which pervades the universe today.

For the last 15 years, James J. (Jamie) Bock, a professor of physics at Caltech and a senior research scientist at JPL, has been searching for a distinctive polarization pattern in the background that gravitational waves from the epoch of inflation may have produced. At 8 p.m. on Wednesday, May 6, 2015, in Caltech's Beckman Auditorium, Bock will discuss how this hunt has led to instruments at the South Pole, on stratospheric balloons, and in outer space. Admission is free.

 

Q: What do you do?

A: I study the early universe empirically, which is often a good approach in a field where we continue to make discoveries driven by new data. My lab builds experiments that address a particular problem is cosmology. Starting out, we think, "What would be the perfect instrument to go after this question?" and that often leads to a new approach. We've been working on the search for B-mode polarization in the microwave background since the year 2000, shortly after theorists came up with the idea that such a polarization signal might be the best way to look for gravitational waves from the era of inflation.

Einstein's equations say that gravitational waves—they stretch and squeeze space and propagate at the speed of light—also have a "handedness." It is similar to how light waves can have a left-handed or a right-handed state. If you look at the cosmic microwave background's polarization across the sky, you can ask yourself, "Which parts of that pattern will look the same in a mirror? Which parts will look different?" The B-mode pattern is the part of the pattern that looks different in a mirror. You can see similar handedness in the brushstrokes of Vincent van Gogh's The Starry Night. A B-mode pattern has to originate from a source that has a handedness, such as gravitational waves. So we're mapping the microwave background to find such a pattern, which in turn will tell us more about how inflation occurred.

 

Q: How do you map polarization?

A: We use detectors called superconducting polarimeters, which are focal plane array detectors developed at JPL. Sometimes, when you figure out the instrument you need, there is a key technology yet to be invented. We dreamed up the basic concept for these detectors in 1999, and JPL has taken them from this initial idea to a fully mature technology.

We previously developed detectors that looked like a spider's web to map temperature variations in the background. These devices were quite successful and flew on the BOOMERanG experiment on a high-altitude balloon and on the Planck satellite in space. However we could see that we needed a completely new approach to map polarization, which led us to superconducting polarimeters. This development is a bit like going from analog film to digital photography. Except here we are literally printing out miniature cameras—the lens, filter, film and a polarizer—on a chip. The detector uses a superconducting thermometer to detect the energy from the background.

The cosmic microwave background means we have to carry out our measurements where microwaves are not strongly affected by the earth's atmosphere. Water vapor copiously absorbs microwave energy. The ideal site from the ground for us is the Antarctic Plateau, where the air is cold and very, very dry. Our observing season at the South Pole begins when the sun goes down for the six-month Antarctic winter, when the air is the driest.

 

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

A: I was a fan of Carl Sagan when I was growing up, and I also really liked a BBC show called Connections, hosted by James Burke. Connections explored the unexpected twists and turns that led to revolutions in technology and science. These often started with a desire to make money or build a new weapon, but that impetus then spawned new technologies, and new ways to use them, that would go off in directions you would never have expected. There's an element of that here—we're using the principles of superconductivity as the best way to explore the very early universe!

As a graduate student at Berkeley I discovered a certain satisfaction in designing instruments developed for a particular purpose, building and testing them, and seeing them actually work. This is hard to explain unless you have actually done it, but maybe the closest analogy is finishing an advanced project in high school shop class. The process definitely requires some patience and determination due to all the steps involved, but once you've built something new, and it works, you want to do it again.

Finally, I am constantly amazed that we can learn so much about something so deeply fundamental as the beginnings of the universe with a small team of scientists. We hunt for imprints from inflation with a team of highly motivated graduate students and postdocs. Our program is exploring the universe some 10–32 seconds after the Big Bang, and the fact that that era is accessible right now, today, if you can just develop the means to do it—well, that is pretty amazing. The early universe is not only knowable, it's within grasp. We live in a special time in history in which we are learning the answers, and some of those answers recently have been deeply surprising. I can't think of anything more exciting than that!

 

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.

Writer: 
Douglas Smith
Writer: 
Exclude from News Hub: 
No
Short Title: 
Vibrations from the Big Bang
News Type: 
Research News

Simon Wins International Mathematics Prize

Barry Simon, the IBM Professor of Mathematics and Theoretical Physics at Caltech, has been awarded the International János Bolyai Prize of Mathematics for 2015 by the Hungarian Academy of Sciences. The prize is given every five years and honors internationally outstanding works in mathematics. As the award was discontinued for almost a century following World War I, Simon, whose work focuses on mathematical physics, is its sixth recipient.

In particular, Simon is being recognized for his book titled Orthogonal Polynomials on the Unit Circle, in which he connects two important fields of mathematics: the theory of orthogonal polynomials and operator theory. Orthogonal polynomials are important in solving, expanding, and interpreting solutions to many kinds of differential equations. Operator theory has fundamental applications in the study of solutions to the Schrödinger equation, which is crucial to an understanding of quantum mechanics. Simon's connection between the fields has led to diverse applications, from probability theory to theoretical physics.

Simon first arrived at Caltech as a Sherman Fairchild Distinguished Visiting Scholar in 1980, joining the faculty permanently in 1981. He is a fellow of the American Academy of Arts and Sciences. He also received the Poincaré Prize in 2012, named for mathematician Henri Poincaré. Poincaré was, incidentally, the first recipient of the Bolyai Prize in 1905.

Hungarian Academy of Sciences President László Lovász will award Simon with the prize at a public session of the academy's Section of Mathematics conference in the second half of 2015.

Writer: 
Exclude from News Hub: 
No
News Type: 
In Our Community

JPL News: NuSTAR Captures Possible Beacons from Dead Stars

Peering into the heart of the Milky Way galaxy, NASA's Nuclear Spectroscopic Telescope Array (NuSTAR) has spotted a mysterious glow of high-energy X-rays that, according to scientists, could be the "howls" of dead stars as they feed on stellar companions.

"We may be witnessing the beacons of a hitherto hidden population of pulsars in the galactic center," said co-author Fiona Harrison of Caltech, principal investigator of NuSTAR. "This would mean there is something special about the environment in the very center of our galaxy."

Read the full story from JPL News

Images: 
Exclude from News Hub: 
No
News Type: 
Research News

Sean Carroll Awarded Guggenheim Fellowship

Sean Carroll, a research professor of physics, has been named a 2015 Fellow of the John Simon Guggenheim Memorial Foundation. Established in 1925, the Guggenheim Fellowship Program awards mid-career fellowships for those who have "demonstrated exceptional capacity for productive scholarship or exceptional creative ability in the arts." This year, the Guggenheim Foundation awarded 173 fellowships, two of which went to physicists.

Carroll came to Caltech in 2006. His research interests are broadly spread across theoretical physics, ranging from cosmology and general relativity to quantum mechanics and particle physics. His proposal to the Guggenheim Foundation, titled "Emergent Structures and the Laws of Physics," focuses on the concept of emergence: how the deepest levels of reality—quantum mechanics, field theory, and space-time—are connected to higher and more complex phenomena, like statistical mechanics and organized structures.

"Since the very notion of complexity does not have a universally-agreed-upon definition, any progress we can make in understanding its basic features is potentially very important," Carroll says in his Guggenheim application.

Carroll has also done research into the relationship between philosophy and physics, particularly within the developing field of philosophy of cosmology. Studies in the field take philosophical approaches to traditional physics problems, such as the arrow of time—the idea that there is a distinction between past and future throughout the observable universe, although the laws of physics would be the same if the direction of time were reversed.

"While science was my first love and remains my primary passion, the philosophical desire to dig deep and ask fundamental questions continues to resonate strongly with me," Carroll says in the "Career Narrative" portion of his application. "I'm convinced that familiarity with modern philosophy of science can be invaluable to physicists trying to tackle questions at the foundations of the discipline."

Home Page Title: 
Theoretical Physicist Awarded Guggenheim Fellowship
Listing Title: 
Theoretical Physicist Awarded Guggenheim Fellowship
Writer: 
Exclude from News Hub: 
No
News Type: 
In Our Community

Understanding the Earth at Caltech

Created by: 
Teaser Image: 
Listing Title: 
Understanding the Earth at Caltech
Frontpage Title: 
Understanding the Earth at Caltech
Slideshow: 
Credit: Courtesy J. Andrade/Caltech

The ground beneath our feet may seem unexceptional, but it has a profound impact on the mechanics of landslides, earthquakes, and even Mars rovers. That is why civil and mechanical engineer Jose Andrade studies soils as well as other granular materials. Andrade creates computational models that capture the behavior of these materials—simulating a landslide or the interaction of a rover wheel and Martian soil, for instance. Though modeling a few grains of sand may be simple, predicting their action as a bulk material is very complex. "This dichotomy…leads to some really cool work," says Andrade. "The challenge is to capture the essence of the physics without the complexity of applying it to each grain in order to devise models that work at the landslide level."

Credit: Kelly Lance ©2013 MBARI

Geobiologist Victoria Orphan looks deep into the ocean to learn how microbes influence carbon, nitrogen, and sulfur cycling. For more than 20 years, her lab has been studying methane-breathing marine microorganisms that inhabit rocky mounds on the ocean floor. "Methane is a much more powerful greenhouse gas than carbon dioxide, so tracing its flow through the environment is really a priority for climate models and for understanding the carbon cycle," says Orphan. Her team recently discovered a significantly wider habitat for these microbes than was previously known. The microbes, she thinks, could be preventing large volumes of the potent greenhouse gas from entering the oceans and reaching the atmosphere.

Credit: NASA/JPL-Caltech

Researchers know that aerosols—tiny particles in the atmosphere—scatter and absorb incoming sunlight, affecting the formation and properties of clouds. But it is not well understood how these effects might influence climate change. Enter chemical engineer John Seinfeld. His team conducted a global survey of the impact of changing aerosol levels on low-level marine clouds—clouds with the largest impact on the amount of incoming sunlight Earth reflects back into space—and found that varying aerosol levels altered both the quantity of atmospheric clouds and the clouds' internal properties. These results offer climatologists "unique guidance on how warm cloud processes should be incorporated in climate models with changing aerosol levels," Seinfeld says.

Credit: Yan Hu/Aroian Lab/UC San Diego

Tiny parasitic worms infect nearly half a billion people worldwide, causing gastrointestinal issues, cognitive impairment, and other health problems. Biologist Paul Sternberg is on the case. His lab recently analyzed the entire 313-million-nucleotide genome of the hookworm Ancylostoma ceylanicum to determine which genes turn on when the worm infects its host. A new family of proteins unique to parasitic worms and related to the early infection process was identified; the discovery could lead to new treatments targeting those genes. "A parasitic infection is a balance between the parasites trying to suppress the immune system and the host trying to attack the parasite," Sternberg observes, "and by analyzing the genome, we can uncover clues that might help us alter that balance in favor of the host."

Credit: K.Batygin/Caltech

Earth is special, not least because our solar system has a unique (as far as we know) orbital architecture: its rocky planets have relatively low masses compared to those around other sun-like stars. Planetary scientist Konstantin Batygin has an explanation. Using computer simulations to describe the solar system's early evolution, he and his colleagues showed that Jupiter's primordial wandering initiated a collisional cascade that ultimately destroyed the first generation population of more massive planets once residing in Earth's current orbital neighborhood. This process wiped the inner solar system's slate clean and set the stage for the formation of the planets that exist today. "Ultimately, what this means," says Batygin, "is that planets truly like Earth are intrinsically not very common."

Credit: Nicolás Wey-Gόmez/Caltech

Human understanding of the world has evolved over centuries, anchored to scientific and technological advancements and our ability to map uncharted territories. Historian Nicolás Wey-Gόmez traces this evolution and how the age of discovery helped shape culture and politics in the modern era. Using primary sources such as letters and diaries, he examines the assumptions behind Europe's encounter with the Americas, focusing on early portrayals of native peoples by Europeans. "The science and technology that early modern Europeans recovered from antiquity by way of the Arab world enabled them to imagine lands far beyond their own," says Wey-Gómez. "This knowledge provided them with an essential framework to begin to comprehend the peoples they encountered around the globe."

Body: 

At Caltech, researchers study the Earth from many angles—from investigating its origins and evolution to exploring its geology and inner workings to examining its biological systems. Taken together, their findings enable a more nuanced understanding of our planet in all its complexity, helping to ensure that it—and we—endure. This slideshow highlights just a few of the Earth-centered projects happening right now at Caltech.

Exclude from News Hub: 
Yes

Pages