Three Caltech faculty members have been awarded the prestigious Sloan Research Fellowship for 2018: Konstantin Batygin, assistant professor of planetary science and Van Nuys Page Scholar; Jim Fuller, assistant professor of theoretical astrophysics; and David Simmons-Duffin, assistant professor of theoretical physics.
The Sloan Research Fellowships, awarded by the Alfred P. Sloan Foundation, "seek to stimulate fundamental research by early-career scientists and scholars of outstanding promise," according to the organization's website. Each year, the Sloan Foundation grants the fellowships to 126 researchers; this year, the awards will come with $65,000 to be spent as the winners see fit.
Konstantin Batygin is a planetary astrophysicist who studies the formation and evolution of planets both within and outside of our solar system. In 2016, working with Mike Brown, the Richard and Barbara Rosenberg Professor of Planetary Astronomy at Caltech, he found evidence for a possible ninth planet orbiting at the outskirts of our solar system, a discovery that led Popular Science to name him one of the "Brilliant 10" researchers later that year.
Jim Fuller is a theorist who uses math, physics, and numerical simulations to tackle astronomy problems, in particular those related to a planet's or star's internal structure and evolution. He studies vibrating cosmic spheres, including "heartbeat" stars, which occur when the light from a pair of orbiting stars pulses with a regular beat; red giant stars, which experience minute pulsations called "starquakes"; and Saturn, whose interior vibrates in ways that can be measured through disturbances to its rings.
David Simmons-Duffin studies strongly coupled quantum field theories, which involve quantum particles that strongly interact. These theories include both quantum mechanics and the laws of special relativity. In particular, he works on so-called conformal field theories (examples of which describe phase transitions in magnets and boiling water). His work has applications in condensed matter physics, particle physics, and quantum gravity.
The first Sloan Research Fellowships were awarded in 1955. According to the Sloan Foundation, 19 past fellows have gone on to earn Nobel Prizes, including three from Caltech: the late Richard Feynman (Nobel Prize for Physics, 1965); Murray Gell-Mann, the Robert Andrews Millikan Professor of Theoretical Physics, Emeritus (Nobel Prize for Physics, 1969); and Kip Thorne (BS '62), the Richard P. Feynman Professor of Theoretical Physics, Emeritus (Nobel Prize for Physics, 2017).
Why is the Arctic warming faster than the rest of the planet? Does mineral dust warm or cool the atmosphere? NASA has selected two new creative research proposals to develop small, space-based instruments that will tackle these fundamental questions about our home planet and its environment: The Polar Radiant Energy in the Far Infrared Experiment (PREFIRE), and the Earth Surface Mineral Dust Source Investigation (EMIT). JPL, administered by Caltech for NASA, is a key participant on both instruments.
Bethany Ehlmann, a professor of planetary science at Caltech, is a co-investigator of EMIT, which will use an imaging spectrometer mounted to the exterior of the International Space Station to determine the mineral composition of land surfaces that produce dust aerosols around the world. By measuring in detail, with visible and infrared light, which minerals make up the dust, EMIT will help to answer the essential question of whether this type of aerosol warms or cools the atmosphere.
"As certain regions grow more arid and desert vegetation is cleared, we are seeing more dust in the atmosphere. In order to gauge what impact this has on climate, we need to analyze the mineral make-up of that dust," says Ehlmann, who is also a JPL research scientist. "The data we gather from EMIT will fill in a big blank in current climate models." Ehlmann will work with JPL's Robert Green, the principal investigator of the project.
Meanwhile, PREFIRE will fly a pair of CubeSats—miniature satellites that are cheaper and lighter than traditional satellites—to probe a little-studied portion of the radiant energy emitted by Earth for clues about Arctic warming, sea ice loss, and ice-sheet melting.
These two instruments were competitively selected from 14 proposals considered under NASA's fourth Earth Venture Instrument opportunity. Earth Venture investigations are small, targeted science investigations that complement NASA's larger missions.
Read the full story from JPL News.
The seven Earth-size planets of TRAPPIST-1 are all mostly made of rock, with some having the potential to hold more water than Earth, according to a new study published in the journal Astronomy and Astrophysics. The planets' densities, now known much more precisely than before, suggest that some planets could have up to 5 percent of their mass in water—which is 250 times more than the oceans on Earth.
The form that water would take on TRAPPIST-1 planets would depend on the amount of heat they receive from their star, which is a mere 9 percent as massive as our sun. Planets closest to the star are more likely to host water in the form of atmospheric vapor, while those farther away may have water frozen on their surfaces as ice. TRAPPIST-1e is the rockiest planet of them all, but still is believed to have the potential to host some liquid water.
"We now know more about TRAPPIST-1 than any other planetary system apart from our own," said Sean Carey, manager of the Spitzer Science Center at Caltech/IPAC in Pasadena, California, and co-author of the new study. "The improved densities in our study dramatically refine our understanding of the nature of these mysterious worlds."
Since the extent of the system was revealed in February 2017, researchers have been working hard to better characterize these planets and collect more information about them. The new study offers better estimates than ever for the planets' densities.
Read the full story from JPL News.
New faculty member Jim Fuller, assistant professor of theoretical astrophysics, studies vibrating cosmic spheres, such as stars with "heartbeats," and the gas giant Saturn, whose pulsations propagate through its rings. He is a theorist who uses math, physics, and numerical simulations to tackle astronomy problems, in particular those related to a planet's or star's internal structure and evolution. Fuller says he fell in love with astronomy when he was young and realized he could use his imagination.
"In astronomy, you think about things you don't encounter in your everyday life, like stars, where you really need to use your imagination because the scale is so large," he says. "But at the same time, astronomy is concrete. There is really something happening out there, and we are applying math and physics to real situations to learn more about our universe."
Fuller received his bachelor's degree from Whitman College in 2008, and his PhD in astronomy and space sciences in 2014 from Cornell University. He joined Caltech as a DuBridge Postdoctoral Fellow in 2013 and joined the Caltech faculty in 2017.
Below Fuller describes, in his own words, some of the movies he has made to illustrate how to "take the pulse" of planets and stars.
The pulsing orbs in this movie are known as "heartbeat" stars. These are binary star systems with very eccentric orbits. At closest approach, which occurs at around seven seconds into the movie, the stars come within a few stellar radii of each other. Their mutual gravitational forces distort the stars into elliptical shapes, changing their observed cross section and apparent brightness. This creates a heartbeat-like pulse in the light curve below the stars.
The brightness changes caused by these so-called tidal distortions have been detected by NASA's Kepler space telescope, leading to the discovery of hundreds of these heartbeat-star systems. Some heartbeat stars do not relax back to their original shape after their closest approach, and they continue to pulsate throughout their orbits as illustrated in this movie. These stellar oscillations cause the stars to dissipate orbital energy, which causes their orbits to circularize. You can also "hear" a heartbeat star below, where I have converted the light curve detected by Kepler into sound and sped things up by a factor of 5 million.
I'm trying to better understand the evolution of heartbeat stars' orbits through a combination of theory and observations.
Like stars, gaseous planets such as Jupiter and Saturn are continually distorted by their own minute pulsations. With Saturn, we cannot see these pulsations directly, but we have learned to use its rings as a giant seismograph. The small gravitational variations caused by pulsations of Saturn exert small torques on orbiting ring particles, generating spiral waves within the rings. These ring disturbances were detected using NASA's Cassini satellite, which later plunged into Saturn in September 2017.
This movie shows an exaggerated example of a pulsation from Saturn propagating around the equator of the planet. The pulsation causes a spiral density wave in the rings that propagates at the same rate. The motion of these spiral patterns then tells us the frequency at which Saturn pulsates, and this can be used to measure properties of the interior of Saturn. My work suggests that Saturn's interior is more complex than previously believed, with an "outer core" composed of a mix of the icy/rocky core material and the gaseous material found in the outer envelope.
Stars in a later stage of evolution, called red giants, exhibit minute pulsations caused by continual "starquakes." Like terrestrial oscillations that occur after earthquakes, starquakes can be used to measure properties of the internal structures of stars because they result from sound waves that propagate through the stellar interior and carry information back to the surface. The movie illustrates a path that a wave would take on its journey between the core and surface of a star if it was able to travel unimpeded. By studying the theory of how waves travel through stars along with some observations of the phenomenon, I helped discover something new about red giants: magnetic fields disrupt the propagation of waves near the core of the star, causing the stellar pulsations to be suppressed. This suppression phenomenon has since been observed in thousands of red giants, suggesting strong internal magnetic fields are more common than we previously believed.
Sixty years ago next week, the hopes of Cold War America soared into the night sky as a rocket lofted skyward above Cape Canaveral, a soon-to-be-famous barrier island off the Florida coast.
The date was Jan. 31, 1958. NASA had yet to be formed, and the honor of this first flight belonged to the U.S. Army. The rocket's sole payload was a javelin-shaped satellite built by the Jet Propulsion Laboratory in Pasadena, California. Explorer 1, as it would soon come to be called, was America's first satellite.
"The launch of Explorer 1 marked the beginning of U.S. spaceflight, as well as the scientific exploration of space, which led to a series of bold missions that have opened humanity's eyes to new wonders of the solar system," said Michael Watkins, current director of JPL. "It was a watershed moment for the nation that also defined who we are at JPL."
In the mid-1950s, both the United States and the Soviet Union were proceeding toward the capability to put a spacecraft in orbit. Yet great uncertainty hung over the pursuit. As the Cold War between the two countries deepened, it had not yet been determined whether the sovereignty of a nation's borders extended upward into space. Accordingly, then-President Eisenhower sought to ensure that the first American satellites were not perceived to be military or national security assets.
Read the full story from JPL News.
In its search for exoplanets—planets outside of our solar system—NASA's Kepler telescope trails behind Earth, measuring the brightness of stars that may potentially host planets. The instrument identifies potential planets around other stars by looking for dips in the brightness of the stars that occur when planets cross in front of, or transit, them. Typically, computer programs flag the stars with these brightness dips, then astronomers look at each one and decide whether or not they truly could host a planet candidate.
Over the three years of the K2 mission, 287,309 stars have been observed, and tens of thousands more roll in every few months. So how do astronomers sift through all that data?
Enter the Exoplanet Explorers citizen scientist project, developed by UC Santa Cruz astronomer Ian Crossfield and Caltech staff scientist Jessie Christiansen. Exoplanet Explorers is hosted on Zooniverse, an online platform for crowdsourcing research.
"People anywhere can log on and learn what real signals from exoplanets look like, and then look through actual data collected from the Kepler telescope to vote on whether or not to classify a given signal as a transit, or just noise," says Christiansen. "We have each potential transit signal looked at by a minimum of 10 people, and each needs a minimum of 90 percent of 'yes' votes to be considered for further characterization."
In early April, just two weeks after the initial prototype of Exoplanet Explorers was set up on Zooniverse, it was featured in a three-day event on the ABC Australia television series Stargazing Live. In the first 48 hours after the project was introduced, Exoplanet Explorers received over 2 million classifications from more than 10,000 users. Included in that search was a brand-new dataset from the K2 mission—the reincarnation of the primary Kepler mission, ended three years ago. K2 has a whole new field of view and crop of stars around which to search for planets. No professional astronomer had yet looked through this dataset, called C12.
Back in California, Crossfield and Christiansen joined NASA astronomer Geert Barentsen, who was in Australia, in examining results as they came in. Using the depth of the transit curve and the periodicity with which it appears, they made estimates for how large the potential planet is and how close it orbits to its star. On the second night of the show, the researchers discussed the demographics of the planet candidates found so far—44 Jupiter-sized planets, 72 Neptune-sized, 44 Earth-sized, and 53 so-called Super Earth's, which are larger than Earth but smaller than Neptune.
"We wanted to find a new classification that would be exciting to announce on the final night, so we were originally combing through the planet candidates to find a planet in the habitable zone—the region around a star where liquid water could exist," says Christiansen. "But those can take a while to validate, to make sure that it really is a real planet and not a false alarm. So, we decided to look for a multi-planet system because it's very hard to get an accidental false signal of several planets."
After this decision, Barentsen left to get a cup of tea. By the time he returned, Christiansen had sorted the crowdsourced data to find a star with multiple transits and discovered a star with four planets orbiting it. Three of the four planets had 100 percent "yes" votes from over 10 people, and the remaining one had 92 percent "yes" votes. This is the first multi-planet system of exoplanets discovered entirely by crowdsourcing.
After the discovery was announced on Stargazing Live, Christiansen and her colleagues continued to study and characterize the system, dubbed K2-138. They statistically validated the set of planet signals as being "extremely likely," according to Christiansen, to be signals from true planets. They also found that the planets are orbiting in an interesting mathematical relationship called a resonance, in which each planet takes almost exactly 50 percent longer to orbit the star than the next planet further in. The researchers also found a fifth planet on the same chain of resonances, and hints of a sixth planet as well. A paper describing the system has been accepted for publication in The Astronomical Journal.
This is the only system with a chain of unbroken resonances in this configuration, and may provide clues to theorists looking to unlock the mysteries of planet formation and migration.
"The clockwork-like orbital architecture of this planetary system is keenly reminiscent of the Galilean satellites of Jupiter," says Konstantin Batygin, assistant professor of planetary science and Van Nuys Page Scholar, who was not involved with the study. "Orbital commensurabilities among planets are fundamentally fragile, so the present-day configuration of the K2-138 planets clearly points to a rather gentle and laminar formation environment of these distant worlds."
"Some current theories suggest that planets form by a chaotic scattering of rock and gas and other material in the early stages of the planetary system's life. However, these theories are unlikely to result in such a closely packed, orderly system as K2-138," says Christiansen. "What's exciting is that we found this unusual system with the help of the general public."
The paper is titled "The K2-138 system: A Near-Resonant Chain of Five Sub-Neptune Planets Discovered by Citizen Scientists." In addition to Christiansen, Crossfield, and Barentsen; other coauthors include Chris Lintott, Campbell Allen, Adam McMaster, Grant Miller, Martin Veldthuis of the University of Oxford; Thomas Barclay of NASA Goddard and the University of Maryland; Brooke Simmons of UC San Diego; Caltech postdoctoral scholar Erik Petigura; Joshua Schlieder of NASA Goddard; Courtney Dressing of UC Berkeley; Andrew Vanderburg of Harvard; Sarah Allen and Zach Wolfenbarger of the Adler Planetarium; Brian Cox of the University of Manchester; Julia Zemiro of the Australian Broadcasting Corporation; Caltech Professor of Astronomy Andrew Howard; John Livingston of the University of Tokyo; Evan Sinukoff of the Australian Broadcasting Corporation and the University of Hawai'i at Manoa; Timothy Catron of Arizona State University; Andrew Grey, Joshua Kusch, Ivan Terentev, and Martin Vales of Zooniverse as part of the University of Oxford; and Martti Kristiansen of the Technical University of Denmark. Funding was provided by the NASA Science Mission Directorate, Google, the Alfred P. Sloan Foundation, NASA, the National Science Foundation, the U.S. Department of Energy, the Japanese Monbukagakusho, the Max Planck Society, and the Higher Education Funding Council for England.
Astronomers have successfully met a major milestone after capturing the very first science data from W. M. Keck Observatory's newest instrument, the Caltech-built Near-Infrared Echelette Spectrometer (NIRES).
The Keck Observatory-Caltech NIRES team recently completed the instrument's first set of commissioning observations and achieved "first light" with a spectral image of the planetary nebula NGC 7027.
"The power of NIRES is that it can cover a whole spectral range simultaneously with one observation," said Keith Matthews, the instrument's principal investigator and chief instrument scientist at Caltech.
Matthews developed the instrument with the help of Tom Soifer, the Harold Brown Professor of Physics, Emeritus, at Caltech and member of the Keck Observatory Board of Directors; Jason Melbourne, a former postdoctoral scholar at Caltech; and Dae-Sik Moon of the University of Toronto, who is also associated with Dunlap Institute and started working on NIRES when he was a Millikan postdoctoral fellow at Caltech about a decade ago.
Because NIRES will be on the telescope at all times, its specialty will be capturing Targets of Opportunity (ToO)—astronomical objects that unexpectedly erupt. This capability is now more important than ever, especially with the recent discovery announced October 16, 2017, of gravitational waves caused by the collision of two neutron stars. For the first time in history, astronomers around the world detected both light and gravitational waves from a cosmic event, triggering a new era in astronomy.
"NIRES will be very useful in this new field of 'multi-messenger' astronomy," said Soifer. "NIRES does not have to be taken off of the telescope, so it can respond very quickly to transient phenomena. Astronomers can easily turn NIRES to the event and literally use it within a moment's notice."
Read the full story from W. M. Keck Observatory at http://www.keckobservatory.org/recent/entry/NIRES.
Millions of years ago, a pair of extremely dense stars, called neutron stars, collided in a violent smash-up that shook space and time. On August 17, 2017, both gravitational waves—ripples in space and time—and light waves emitted during that neutron star merger finally reached Earth. The gravitational waves came first and were detected by the twin detectors of the National Science Foundation (NSF)-funded Laser Interferometry Gravitational-wave Observatory (LIGO), aided by the European Virgo observatory. The light waves were observed seconds, days, and months later by dozens of telescopes on the ground and in space.
Now, scientists from Caltech and several other institutions are reporting that light with radio wavelengths continues to brighten more than 100 days after the August 17 event. These radio observations indicate that a jet, launched from the two neutron stars as they collided, is slamming into surrounding material and creating a slower-moving, billowy cocoon.
"We think the jet is dumping its energy into the cocoon," says Gregg Hallinan, an assistant professor of astronomy at Caltech. "At first, people thought the material from the collision was coming out in a jet like a firehose, but we are finding that that the flow of material is slower and wider, expanding outward like a bubble."
The findings, made with the Karl G. Jansky Very Large Array in New Mexico, the Australia Telescope Compact Array, and the Giant Metrewave Radio Telescope in India, are reported in a new paper in the December 20 online issue of the journal Nature. The lead author is Kunal Mooley (PhD '15), formerly of the University of Oxford and now a Jansky Fellow at Caltech.
The new data argue against a popular theory describing the aftermath of the neutron star merger—a theory that proposes the event created a fast-moving and beam-like jet thought to be associated with extreme blasts of energy called gamma-ray bursts, and in particular with short gamma-ray bursts, or sGRBs. Scientists think that sGRBs, which pop up every few weeks in our skies, arise from the merger of a pair of neutron stars or the merger of a neutron star with a black hole (an event that has yet to be detected by LIGO). An sGRB is seen when the jet points exactly in the direction of Earth.
On August 17, NASA's Fermi Gamma-ray Space Telescope and the European INTErnational Gamma-Ray Astrophysics Laboratory (INTEGRAL) missions detected gamma rays just seconds after the neutron stars merged. The gamma rays were much weaker than what is expected for sGRBS, so the researchers reasoned that a fast and narrowly focused jet was produced but must have been pointed slightly askew from the direction of Earth, or off-axis.
The radio emission—originally detected 16 days after the August 17 event and still measurable and increasing in strength as of December 2—tells a different story. If the jet had been fast and beam-like, the radio light would have weakened with time as the jet lost energy. The fact that the brightness of the radio light is increasing instead suggests the presence of a cocoon that is choking the jet. The reason for this is complex, but it has to do with the fact that the slower-moving, wider-angle material of the cocoon gives off more radio light than the faster-moving, sharply focused jet material.
"It's like the jet was fogged out," says Mooley. "The jet may be off-axis, but it is not a simple pointed beam or as fast as some people thought. It may be blocked off by material thrown off during the merger, giving rise to a cocoon and emitting light in many different directions."
This means that the August 17 event was not a typical sGRB as originally proposed.
"Standard sGRBs are 10,000 times brighter than we saw for this event," says Hallinan. "Many people thought this was because the gamma-ray emission was off-axis and thus much weaker. But it turns out that the gamma rays are coming from the cocoon rather than the jet. It is possible that the jet managed to eventually break out through the cocoon, but we haven't seen any evidence for this yet. It is more likely that it got trapped and snuffed out by the cocoon."
The possibility that a cocoon was involved in the August 17 event was originally proposed in a study led by Caltech's Mansi Kasliwal (MS '07, PhD '11), assistant professor of astronomy, and colleagues. She and her team from the NSF-funded Global Relay of Observatories Watching Transients Happen (GROWTH) project observed the event at multiple wavelengths using many different telescopes.
"The cocoon model explains puzzling features we have observed in the neutron star merger," says Kasliwal. "It fits observations across the electromagnetic spectrum, from the early blue light we witnessed to the radio waves and X-rays that turned on later. The cocoon model had predicted that the radio emission would continue to increase in brightness, and that's exactly what we see."
The researchers say that future observations with LIGO, Virgo, and other telescopes will help further clarify the origins and mechanisms of these extreme events. The observatories should be able to detect additional neutron star mergers—and perhaps eventually, mergers of neutron stars and black holes.
Work at Caltech on this study, titled "A mildly relativistic wide-angle outflow in the neutron star merger GW170817," was funded by the NSF, the Sloan Research Foundation, and Research Corporation for Science Advancement. Other Caltech authors are Kishalay De, a graduate student, and Shri Kulkarni, George Ellery Hale Professor of Astronomy and Planetary Science.
If you could fly aboard NASA's Dawn spacecraft, the surface of dwarf planet Ceres would generally look quite dark, but with notable exceptions. These exceptions are the hundreds of bright areas that stand out in images Dawn has returned. Now, scientists have a better sense of how these reflective areas formed and changed over time -- processes indicative of an active, evolving world.
"The mysterious bright spots on Ceres, which have captivated both the Dawn science team and the public, reveal evidence of Ceres' past subsurface ocean, and indicate that, far from being a dead world, Ceres is surprisingly active. Geological processes created these bright areas and may still be changing the face of Ceres today," said Carol Raymond, deputy principal investigator of the Dawn mission, based at NASA's Jet Propulsion Laboratory in Pasadena, California. Raymond and colleagues presented the latest results about the bright areas at the American Geophysical Union meeting in New Orleans on Tuesday, Dec. 12. Their findings were also published in the journal Icarus in a new study led by Nathan Stein, a doctoral researcher at Caltech.
Caltech is proceeding to decommission the Caltech Submillimeter Observatory (CSO) on Hawaii Island's Maunakea. CSO began operations in 1987 and ceased scientific observations in September 2015.
The next steps are an environmental assessment (EA) and a conservation district use application (CDUA). A "public scoping period," open until January 15, 2018, is the first opportunity the community will have to comment on removal and site restoration. There will be additional opportunities, including formal comment periods, once the drafts of the EA and CDUA are released.
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