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Mystery of the Universe's Gamma-Ray Glow Solved
February 5, 2015
The steady glow of high-energy gamma-ray light that spreads across the cosmos has puzzled astronomers for decades. One team of researchers thinks it has the best explanation yet for the source of this strange emission.
After observing the universe with NASA's Fermi Gamma-ray Space Telescope for six years, scientists with the mission say the majority of the gamma-ray glow they have seen can be explained by objects already known to science. If there are any as-yet unknown sources out there, their contribution to the glow would be very small, scientists say.
"We have a very plausible story. We're not 100 percent confident that this is the final answer, but it really constrains what other exotic possibilities could be out there," said Keith Bechtol, a postdoctoral researcher at the University of Chicago and a member of the Fermi collaboration who worked on the analysis.Learn more >>
One Hundred Years of General Relativity
March 6, 2015
Albert Einstein published his theory of general relativity 100 years ago. The theory has shaped the idea of black holes, pulsars, and modern cosmology. Science historian David Kaiser guides us through the history of Einstein's insight, and physicists Michael Turner and Alex Filippenko discuss where the theory might take us in the future.
Scientists find rare dwarf satellite galaxy candidates in Dark Energy Survey data
March 11, 2015
Scientists on two continents have independently discovered a set of celestial objects that seem to belong to the rare category of dwarf satellite galaxies orbiting our home galaxy, the Milky Way.
Dwarf galaxies are the smallest known galaxies, and they could hold the key to understanding dark matter and the process by which larger galaxies form.
A team of researchers with the Dark Energy Survey, headquartered at the U.S. Department of Energy's Fermi National Accelerator Laboratory, and an independent group from the University of Cambridge jointly announced their findings today. Both teams used data taken during the first year of the Dark Energy Survey, all of which is publicly available, to carry out their analysis.
"The large dark matter content of Milky Way satellite galaxies makes this a significant result for both astronomy and physics," said Alex Drlica-Wagner of Fermilab, one of the leaders of the Dark Energy Survey analysis.
Satellite galaxies are small celestial objects that orbit larger galaxies, such as our own Milky Way. Dwarf galaxies can be found with fewer than 100 stars and are remarkably faint and difficult to spot. (By contrast, the Milky Way, an average-sized galaxy, contains billions of stars.)
These newly discovered objects are a billion times dimmer than the Milky Way and a million times less massive. The closest of them is about 100,000 light-years away.
"The discovery of so many satellites in such a small area of the sky was completely unexpected," said Cambridge's Institute of Astronomy's Sergey Koposov, the Cambridge study's lead author. "I could not believe my eyes."
Scientists have previously found more than two dozen of these satellite galaxies around our Milky Way. About half of them were discovered in 2005 and 2006 by the Sloan Digital Sky Survey, the precursor to the Dark Energy Survey. After that initial explosion of discoveries, the rate fell to a trickle and dropped off entirely over the past five years.
The Dark Energy Survey is looking at a new portion of the southern hemisphere, covering a different area of sky than the Sloan Digital Sky Survey. The galaxies announced today were discovered in a search of only the first of the planned five years of Dark Energy Survey data, covering roughly one-third of the portion of sky that DES will study. Scientists expect that the full Dark Energy Survey will find up to 30 of these satellite galaxies within its area of study.
Atlas image obtained as part of the Two Micron All Sky Survey (2MASS), a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center/California Institute of Technology, funded by the National Aeronautics and Space Administration and the National Science Foundation.
While more analysis is required to confirm any of the observed celestial objects as satellite galaxies, researchers note their size, low surface brightness and significant distance from the center of the Milky Way as evidence that they are excellent candidates. Further tests are ongoing, and data collected during the second year of the Dark Energy Survey could yield more of these potential dwarf galaxies to study.
Newly discovered galaxies would also present scientists with more opportunities to search for signatures of dark matter. Dwarf satellite galaxies are dark matter-dominated, meaning they have much more mass in unseen matter than in stars. The nature of this dark matter remains unknown but might consist of particles that annihilate each other and release gamma rays. Because dwarf galaxies do not host other gamma ray sources, they make ideal laboratories to search for signs of dark matter annihilation. Scientists are confident that further study of these objects will lead to even more sensitive searches for dark matter.
In a separate result also announced today, the Large Area Telescope Collaboration for NASA's Fermi Gamma-Ray Telescope mission reported that they did not see any significant excess of gamma ray emission associated with the new Dark Energy Survey objects. This result demonstrates that new discoveries from optical telescopes can be quickly translated into tests of fundamental physics.
"We did not detect significant emission with the LAT, but the dwarf galaxies that DES has and will discover are extremely important targets for the dark matter search," said Peter Michelson, spokesperson for the LAT collaboration. "If not leading to an identification of particle dark matter, they will certainly be useful to constrain its properties."
The Dark Energy Survey is a five-year effort to photograph a large portion of the southern sky in unprecedented detail. Its primary instrument is the Dark Energy Camera, which - at 570 megapixels - is the most powerful digital camera in the world, able to see galaxies up to 8 billion light-years from Earth. Built and tested at Fermilab, the camera is now mounted on the 4-meter Victor M. Blanco telescope at the Cerro Tololo Inter-American Observatory in the Andes Mountains in Chile.
The survey's five-year mission is to discover clues about the nature of dark energy, the mysterious force that makes up about 70 percent of all matter and energy in the universe. Scientists believe that dark energy may be the key to understanding why the expansion of the universe is accelerating.
"The Dark Energy Camera is a perfect instrument for discovering small satellite galaxies," said Keith Bechtol of the Kavli Institute for Cosmological Physics at the University of Chicago, who helped lead the Dark Energy Survey analysis. "It has a very large field of view to quickly map the sky and great sensitivity, enabling us to look at very faint stars. These results show just how powerful the camera is and how significant the data it collects will be for many years to come."
The Dark Energy Survey is a collaboration of more than 300 scientists from 25 institutions in six countries.Learn more >>
John E. Carlstrom, Thomas M. Crawford and Lloyd Knox, "Particle physics and the cosmic microwave background"
March 13, 2015
Temperature and polarization variations across the microwave sky include the fingerprints of quantum fluctuations in the early universe. They may soon reveal physics at unprecedented energy scales.
The detection of the CMB and the consensus that the universe had a hot and dense early phase led to a fertile relationship between cosmology and particle physics. The hot early universe was a natural particle accelerator that could reach energies well beyond what laboratories on Earth will attain in the foreseeable future. Precise measurements of both the spectrum of the CMB and its tiny variations in brightness from one point to another on the sky reflect the influences of high-energy processes in the early cosmos.
For instance, the gravitational effects of neutrinos have been detected at high significance; such measurements imply that the sum of the neutrino masses is no more than a few tenths of an eV. The CMB data also show the influence of helium produced in the early universe and thus constrain the primordial helium fraction. Moreover, the data are nearly impossible to fit without dark energy and dark matter - two ingredients missing from the standard model of particle physics.Learn more >>
Horizon 2015 : Dancing in the Dark - The End of Physics?
March 30, 2015
Scientists genuinely don't know what most of our universe is made of. The atoms we're made from only make up four per cent. The rest is dark matter and dark energy (for 'dark', read 'don't know'). The Large Hadron Collider at CERN has been upgraded. When it's switched on in March 2015, its collisions will have twice the energy they did before. The hope is that scientists will discover the identity of dark matter in the debris.
The stakes are high - because if dark matter fails to show itself, it might mean that physics itself needs a rethink.Learn more >>
Mapping dark matter may help solve a cosmic mystery
April 15, 2015
Scientists have announced the creation of the largest map yet of the invisible material that helps make up the universe, what's known as dark matter.
Jeffrey Brown explores some of the very cosmic questions around this story.
JEFFREY BROWN: That's worth saying again: We can't see it, but we can apparently map it. What's called dark matter is, in fact, everywhere, and it's believed to play a crucial role in forming and holding together galaxies with its gravitational pull.
In findings announced Monday, researchers used a dark energy camera and a large telescope in Northern Chile to create this color-coded map, showing a small piece of the visible sky. Orange and red areas represent denser concentrations of dark matter. Blue areas are less dense.Learn more >>
Scientists Release Largest Map Yet Of Dark Matter In The Cosmos
April 15, 2015
Researchers from the Dark Energy Survey used data captured by the Dark Energy Camera, a 570-megapixel imaging device they say is one of the world's most powerful digital cameras, to put together the largest contiguous map of dark matter created. They presented their findings Monday at a meeting of the American Physical Society in Baltimore.
The scientists say the map covers only about 3 percent of the area of sky. They hope it will improve understanding of the role dark matter plays in the creation of galaxies - and to investigate dark energy.
"We measured the barely perceptible distortions in the shapes of about 2 million galaxies to construct these new maps," Vinu Vikram of Argonne National Laboratory, one of the lead scientists on the study, said in a statement Monday. "They are a testament not only to the sensitivity of the Dark Energy Camera, but also to the rigorous work by our lensing team to understand its sensitivity so well that we can get exacting results from it."
The Fermi National Accelerator Laboratory built and tested the camera, which is mounted on the 4-meter Victor M. Blanco telescope at the Cerro Tololo Inter-American Observatory in Chile. The National Center for Supercomputing Applications at the University of Illinois in Urbana-Champaign processed the data that went into the map.
Here's more from the statement:
"As scientists expand their search, they will be able to better test current cosmological theories by comparing the amounts of dark and visible matter.
"Those theories suggest that, since there is much more dark matter in the universe than visible matter, galaxies will form where large concentrations of dark matter (and hence stronger gravity) are present. So far, the DES analysis backs this up: The maps show large filaments of matter along which visible galaxies and galaxy clusters lie and cosmic voids where very few galaxies reside. Follow-up studies of some of the enormous filaments and voids, and the enormous volume of data, collected throughout the survey will reveal more about this interplay of mass and light."
"Our analysis so far is in line with what the current picture of the universe predicts," said Chihway Chang, another of the lead scientists who is with ETH Zurich. "Zooming into the maps, we have measured how dark matter envelops galaxies of different types and how together they evolve over cosmic time. We are eager to use the new data coming in to make much stricter tests of theoretical models."
The Dark Energy Survey is on the second year of a five-year study.Learn more >>
Virtual Telescope Expands to See Black Holes
April 21, 2015
University of Arizona News
Astronomers building an Earth-size virtual telescope capable of photographing the event horizon of the black hole at the center of our Milky Way have extended their instrument to the bottom of the Earth - the South Pole - thanks to recent efforts by a team led by Dan Marrone of the University of Arizona.
Marrone, an assistant professor in the UA's Department of Astronomy and Steward Observatory, and several colleagues flew to the National Science Foundation's Amundsen-Scott South Pole Station in December to bring the South Pole Telescope, or SPT, into the largest virtual telescope ever built - the Event Horizon Telescope, or EHT. By combining telescopes across the Earth, the EHT will take the first detailed pictures of black holes.
The EHT is an array of radio telescopes connected using a technique known as Very Long Baseline Interferometry, or VLBI. Larger telescopes can make sharper observations, and interferometry allows multiple telescopes to act like a single telescope as large as the separation - or "baseline" - between them.
"Now that we've done VLBI with the SPT, the Event Horizon Telescope really does span the whole Earth, from the Submillimeter Telescope on Mount Graham in Arizona, to California, Hawaii, Chile, Mexico, Spain and the South Pole," Marrone said. "The baselines to SPT give us two to three times more resolution than our past arrays, which is absolutely crucial to the goals of the EHT. To verify the existence of an event horizon, the 'edge' of a black hole, and more generally to test Einstein's theory of general relativity, we need a very detailed picture of a black hole. With the full EHT, we should be able to do this."
The prime EHT target is the Milky Way's black hole, known as Sagittarius A* (pronounced "A-star"). Even though it is 4 million times more massive than the sun, it is tiny to the eyes of astronomers. Because it is smaller than Mercury's orbit around the sun, yet almost 26,000 light-years away, studying its event horizon in detail is equivalent to standing in California and reading the date on a penny in New York.
With its unprecedented resolution, more than 1,000 times better than the Hubble Space Telescope, the EHT will see swirling gas on its final plunge over the event horizon, never to regain contact with the rest of the universe. If the theory of general relativity is correct, the black hole itself will be invisible because not even light can escape its immense gravity.
First postulated by Albert Einstein's general theory of relativity, the existence of black holes has since been supported by decades' worth of astronomical observations. Most if not all galaxies are now believed to harbor a supermassive black hole at their center, and smaller ones formed from dying stars should be scattered among their stars. The Milky Way is known to be home to about 25 smallish black holes ranging from five to 10 times the sun's mass. But never has it been possible to directly observe and image one of these cosmic oddities.
Weighing 280 tons and standing 75 feet tall, the SPT sits at an elevation of 9,300 feet on the polar plateau at Amundsen-Scott, which is located at the geographic South Pole. The University of Chicago built SPT with funding and logistical support from the NSF's Division of Polar Programs. The division manages the U.S. Antarctic Program, which coordinates all U.S. research on the southernmost continent.
The 10-meter SPT operates at millimeter wavelengths to make high-resolution images of cosmic microwave background radiation, the light left over from the Big Bang. Because of its location at the Earth's axis and at high elevation where the polar air is largely free of water vapor, it can conduct long-term observations to explore some of the biggest questions in cosmology, such as the nature of dark energy and the process of inflation that is believed to have stretched the universe exponentially in a tiny fraction of the first second after the Big Bang.
"We are thrilled that the SPT is part of the EHT," said John Carlstrom, who leads the SPT collaboration. "The science, which addresses fundamental questions of space and time, is as exciting to us as peering back to the beginning of the universe."
To incorporate the SPT into the EHT, Marrone's team constructed a special, single-pixel camera that can sense the microwaves hitting the telescope. The Academia Sinica Institute for Astronomy and Astrophysics in Taiwan provided the atomic clock needed to precisely track the arrival time of the light. Comparing recordings made at telescopes all over the world allows the astronomers to synthesize the immense telescope. The Smithsonian Astrophysical Observatory and Haystack Observatory of the Massachusetts Institute of Technology provided equipment to record the microwaves at incredibly high speeds, generating nearly 200 terabytes per day.
"To extend the EHT to the South Pole required improving our data capture systems to record data much more quickly than ever before," said Laura Vertatschitsch of the Smithsonian Astrophysical Observatory. A new "digital back end," developed by Vertatschitsch and colleagues, can process data four times faster than its predecessor, which doubles the sensitivity of each telescope.
For their preliminary observations, Marrone's team trained its instrument on two known black holes, Sagittarius A* in our galaxy, and another, located 10 million light-years away in a galaxy named Centaurus A. For this experiment, the SPT and the Atacama Pathfinder Experiment, or APEX, telescope in Chile observed together, despite being nearly 5,000 miles apart. These data constitute the highest- resolution observations ever made of Centaurus A (though the information from a single pair of telescopes cannot easily be converted to a picture).
"VLBI is very technically challenging, and a whole system of components had to work perfectly at both SPT and APEX for us to detect our targets," said Junhan Kim, a doctoral student at the UA who helped build and install the SPT EHT receiver. "Now that we know how to incorporate SPT, I cannot wait to see what we can learn from a telescope 10,000 miles across."
The next step will be to include the SPT in the annual EHT experiments that combine telescopes all over the world. Several new telescopes are prepared to join the EHT in the next year, meaning that the next experiment will be the largest both geographically and with regard to the number of telescopes involved. The expansion of the array is supported by the National Science Foundation Division of Astronomical Sciences through its new Mid-Scale Innovations Program, or MSIP.
Shep Doeleman, who leads the EHT and the MSIP award, noted that "the supermassive black hole at the Milky Way's center is always visible from the South Pole, so adding that station to the EHT is a major leap toward bringing an event horizon into focus."
This work was funded through NSF grants AST-1207752 to Marrone; AST-1207704 to Doeleman at MIT's Haystack Observatory; and AST-1207730 to Carlstrom at the University of Chicago.
An international research collaboration led by the University of Chicago manages the SPT. The NSF-funded Physics Frontier Center of the Kavli Institute for Cosmological Physics, the Kavli Foundation, and the Gordon and Betty Moore Foundation provide partial support.
The APEX telescope, located in Chile's Atacama Desert, is a collaboration of the European Southern Observatory, the Max Planck Institute for Radioastronomy and the Onsala Space Observatory in Sweden.Learn more >>
Earth-sized telescope expands to the South Pole to see black holes in detail
April 21, 2015
The University of Chicago News Office
Astronomers building an Earth-sized virtual telescope capable of photographing the event horizon of the black hole at the center of our Milky Way have extended their instrument to include the University of Chicago-built South Pole Telescope.
The South Pole Telescope, situated at the National Science Foundation's Amendsen-Scott South Pole Station, now is part of the largest virtual telescope ever built - the Event Horizon Telescope. By combining telescopes across the Earth, the Event Horizon Telescope will take the first detailed pictures of black holes.
"We are thrilled that the South Pole Telescope is part of the EHT. The science, which addresses fundamental questions of space and time, is as exciting to us as peering back to the beginning of the universe," said UChicago Prof. John Carlstrom, who leads the SPT collaboration.
The Event Horizon Telescope is an array of radio telescopes connected using a technique known as Very Long Baseline Interferometry. Larger telescopes can make sharper observations, and interferometry allows multiple telescopes to act like a single telescope as large as the separation, or "baseline," between them.
Now that the technique has been extended to the South Pole Telescope, the Event Horizon Telescope spans the entire Earth, from the Submillimeter Telescope on Mount Graham in Arizona, to California, Hawaii, Chile, Mexico, Spain and the South Pole.Learn more >>
Live Session with Michael Turner
May 1, 2015
World Science U Master Class with Michael Turner
Tue Mar, 10 2015 2PM - 3PM (CDT)
Michael Turner, theoretical cosmologist and Director of the Kavli Institute for Cosmological Physics at the University of Chicago, leads a free Master Class focusing on dark energy. The class is part of World Science U's Master Class offering - giving you the opportunity to learn directly from the world's greatest thinkers. Professor Turner hosted a live online session on March 10th, 2015 to answer your questions and delve deeper into the material.Learn more >>
UChicago celebrates the promise of Chicago youth
May 25, 2015
The University of Chicago News Office
Though Daweed Abdiel always has been intellectually curious and a good student, college wasn't always on his radar. Most of his older family members had started college but never finished. In his first two years of high school, "I wasn't thinking about college too much," he said. "I was a good student, but I had no direction."
That changed after Abdiel joined the Upward Bound program offered through the Office of Special Programs-College Prep. Staff members who lead the program encouraged him to apply to colleges. "This program helped me determine I wanted a small liberal arts college." With Upward Bound showing the way, he got what he wanted. In August, Abdiel will attend Denison University with the support of two prestigious awards: a Gates-Millennium Scholarship and a Posse Scholarship.
"We have young people who develop a real sense of confidence and self-awareness about who they are and their ability to meet challenges and be successful," said Dovetta McKee, director of the Office of Special Programs-College Prep. "It changes their mindset about the leadership role they can play in their communities, and makes them models for young people who follow behind them," she said.
Abdiel was one of about 60 Chicago high school seniors honored at the 2015 Student Recognition Night, sponsored by the Office of Civic Engagement. The seniors took part in one of two programs: Upward Bound or the Collegiate Scholars Program, which prepares talented Chicago Public Schools students to succeed in the nation's top colleges and universities.
In addition, University students who have served with the Neighborhood Schools Program received recognition for their work in local public schools and community programs. All three efforts are part of UChicago Promise, the University's multi-pronged effort to increase college access and success for Chicago youth.
Increasing college access and success starts young. The Neighborhood Schools Program connects 375 UChicago students with 3,000 students in the surrounding neighborhoods. Many are still grade-schoolers, and tutoring can make a real impact on their future prospects.
"We leaned on NSP quite a lot and they came through," said Ed Kajor in a video shown at the event. Kajor, a learning behavior specialist at Burke Elementary in Washington Park, credits tutoring from volunteers like Amanda Weisler, a third-year sociology major, for boosting the school's scores on standardized tests.
"Our program is one of a few that is truly receptive to local school needs, said Shaz Rasul, director of community programs in the Office of Civic Engagement. "If a principal tells us she needs help with third grade, we will find tutors for the third grade who can be available during the school day. This is important because schools are often judged by what happens in the classroom, not enrichment time after school."
University students benefit, too. Real-world experience has led more than one NSP volunteer into a career in education, from Sara Stoelinga, who was honored at the event with the Don York Faculty Initiative Award, to keynote speaker Geoffrey Aladro AB'06, who is currently Miami-Dade's Teacher of the Year.
When Aladro discovered his long-held dream of corporate work wasn't all he thought it would be, he changed gears and chose teaching because of his NSP experiences. "I haven't really worked since I became a teacher," he told the crowd, "because I love my work."
Fourth-year Jonathan Fifer, who volunteered with NSP throughout his College career, intends to follow in their footsteps. His next goal will be to earn a master's degree from Teachers College, Columbia University, where he'll study early childhood education. "I've always been interested in the little kids," he said. "Even when they're crying or being bad, you can see their thought process. I can't be mad at them."
While teaching high school students about the college application process gets them started on their higher education journey, the Upward Bound and Collegiate Scholars programs also support young people's intellectual growth. Ivelise Colon, a Collegiate Scholar, has chosen Whittier College's alternative liberal arts program, where she will design her own major, incorporating elements of psychology, sociology and early childhood education. "I want to do my own thing," she said.
"The hallmark of Collegiate Scholars is the interaction with faculty. We are one of very few institutions in the country where there is intentional engagement between University faculty and public school students from across the city," said Abel Ochoa, interim director of the Collegiate Scholars Program. "It really elevates a student's frame of thinking to be taught by a professor who has written a textbook, done concrete research, or is considered a world-renowned expert in his field."
Like Colon, Abdiel has seen his intellectual interests shift over time, from physics to chemistry with a generous side helping of economics and African-American Studies. He credits his Upward Bound mentors for exposing him to the Kavli Institute of Cosmological Physics and for staying the course with him as his interests evolved. "They won't tell you what to do, but they'll ask you questions," he said. "They'll help you find your passions."Learn more >>
Students in arts and sciences influence, benefit each other
May 29, 2015
The University of Chicago News Office
This year, in a new partnership with the School of the Art Institute of Chicago, the Arts, Science & Culture Initiative awarded grants to five teams composed of nine UChicago and three SAIC graduate students.
The goal of providing these collaborative grants is "to test the idea that different domains of knowing and knowledge -- arts, science and culture -- can enrich and influence each discipline's particular questions, tools, methodologies and specific curiosities," said Julie Marie Lemon, the program's director and curator.
The collaborative efforts between the students of arts, science and culture resulted in creative projects that were presented in early May.
One of the projects was "The Fabric of the Universe," created by Isaac Facio, a master of fine arts candidate in fiber and material studies at SAIC, and Benedikt Diemer, a UChicago PhD candidate in astrophysics. This project used computer simulations of dark matter and translated them into a more tangible form using three-dimensional textiles, resulting in a novel way of visualizing the structure of the universe.
Diemer said that the project has offered a new perspective for his research in astrophysics.
"Our project has caused me to look at my data in 3-D where I previously only made 2-D visualizations. This has definitely improved my understanding of the dark matter structures in my simulations," he said.
As a testament to the novel insights offered by this project, "'The Fabric of the Universe' was awarded a grant from the renowned TextielLab, part of the TextielMuseum, in Tilburg, the Netherlands, to produce the fabric," said Lemon, the program director.
And each year, Lemon noted, "the collaborations and the projects have become more and more sophisticated, and more students become interested in the initiative."Learn more >>
Honoring graduate teachers and mentors: Prof. Angela Olinto
June 1, 2015
The University of Chicago News Office
The 2015 Faculty Award for Excellence in Graduate Teaching and Mentoring
Angela V. Olinto
Homer J. Livingston Professor, Astronomy & Astrophysics
When Angela Olinto entered graduate school in physics at the Massachusetts Institute of Technology in 1982, there were two women and 60 men in her class. But over her 21 years at the University of Chicago, Olinto has welcomed 10 women and five men as graduate students into her research group, which specializes in particle astrophysics and cosmology.
"It's thrilling to look back and realize I've had about 70 percent women in my group, which is not something I planned," Olinto says. "It's been a colorful and brilliant group, lots of different nationalities and personalities, lots of different points of view. I've always learned as much from them as I taught them."
Olinto's students now have dispersed across the country and around the world. But many of them came together via email to nominate Olinto for the Faculty Award for Excellence in Graduate Teaching and Mentoring. Coordinating the effort was Olinto's current graduate student, Ke Fang, who graduates this summer.
"Independent of actually receiving the award, just the nomination itself was a great honor to me," Olinto says.Learn more >>
Prof. Daniel Holz receives Quantrell Award
June 1, 2015
The University of Chicago News Office
The Llewellyn John and Harriet Manchester Quantrell Awards are believed to be the nation's oldest prize for undergraduate teaching. Presented annually, the awards reflect the College's commitment to honoring inspiring teachers. UChicago faculty often count the Quantrell among their most treasured honors.
"Ernest Quantrell, who first established the Quantrell Awards in 1937, wanted to honor faculty members who were great scholar-teachers and who inspired our students to become more enlightened thinkers and more effective citizens of their communities and of our nation," says John W. Boyer, dean of the College. "As teachers and as scholars and as citizens of the University at large, this year's Quantrell winners exemplify the very best about the College and the University."
Daniel Holz, Associate Professor, Physics
Soon after Daniel Holz learned of his Quantrell Award, he looked up the list of previous recipients.
"I was actually a graduate student here at UChicago, and I've had some of the previous recipients as professors. They're truly outstanding," says Holz, PhD'98, an associate professor in physics. "It's really an honor to be on the same list."Learn more >>
2015 Gruber Prize in Cosmology: John E. Carlstrom
June 9, 2015
The Gruber Foundation
The 2015 Gruber Prize in Cosmology honors theorist Jeremiah P. Ostriker for his lifetime of achievements and the experimentalists John E. Carlstrom and Lyman A. Page, Jr., for their pioneering observations of the cosmic microwave background (CMB), the relic radiation from the infancy of the universe's existence. Individually and collectively the works of these three scientists has helped to establish and advance the standard cosmological model: a universe that arose out of an inconceivably dense state of matter and energy, and has been expanding and cooling ever since, eventually coalescing into today's familiar skyscape of planets, stars, and galaxies.
During a five-decade career at Princeton University, Jeremiah Ostriker has made significant contributions to the studies of galaxy formation, the interstellar medium, and the intergalactic medium. He has also repeatedly challenged assumptions about how the universe works and proposed radical alternative interpretations. In 1972 he and Princeton colleague P. James E. Peebles created computer simulations that indicated either Newton's law of gravitation is wrong or some sort of invisible mass must be present to stabilize rotating spiral galaxies such as our own Milky Way. A year later, in collaboration with a postdoctoral fellow, Ostriker and Peebles surveyed existing data from a wide array of observations of individual galaxies and clusters of galaxies and concluded, in the opening sentence of a now-classic paper: "There are reasons, increasing in number and quality, to believe that the mass of ordinary galaxies may have been underestimated by a factor of 10 or more."
In 1995, Ostriker and another Princeton colleague, Paul J. Steinhardt, argued that the total amount of matter in the universe, dark or otherwise, is at odds with some key theoretical implications of the Big Bang interpretation of the universe. Ostriker and Steinhardt invoked yet another mysterious missing component that they said should be permeating the universe.
Today we call the missing components that Ostriker proposed in the 1970s and 1990s dark matter and dark energy, respectively -- abstract ideas that have been borne out by innumerable observations. In fact, while other theorists were making arguments similar to that of Ostriker and Steinhardt in the mid-1990s, what distinguishes their paper is the suggestion that this component should contribute about 70 percent to the total mass and energy of the universe --a figure validated by many later observations, including those made by the instruments overseen by Carlstrom and Page.
While both Page and Carlstrom have worked extensively in the study of the CMB, they lead two projects in particular. Carlstrom, who has been at the University of Chicago since 1995, is the principal investigator on the South Pole Telescope, which was constructed at the U. S. science station at the Pole in late 2006 and early 2007. Page, who has been at Princeton since 1990, serves in the same capacity for the Atacama Cosmology Telescope, which was constructed on Cerro Toco in the mountainous Atacama Desert in Chile in 2007.
Those instruments, both still active, probe the CMB, the relic radiation dating to the infancy of the cosmos. When the universe was 380,000 years old it had cooled enough for hydrogen atoms and photons to decouple and go their separate ways. That "flashbulb" moment has survived as a sort of snapshot -- a "baby picture" of the universe-- though over the past 13.7 billion years the expansion of space has stretched the light from the image all the way into the microwave end of the electromagnetic spectrum. Look closely enough and finely enough at the CMB, though, and you should be able to see extraordinarily subtle shadings in temperature: the DNA for the galaxies, clusters of galaxies, and super-clusters of galaxies that populate the universe as we know it.
Among the many contributions to cosmology that the South Pole Telescope and the Atacama Cosmology Telescope have made are: the discovery of hundreds of clusters of galaxies going back to when the universe was about one-third its present age, providing a history of the growth of the large-scale structure of the universe; independent verification that the universe consists of approximately 25 percent dark matter, 70 percent dark energy, and 5 percent atoms; and strong evidence that the structure in the CMB is a remnant of quantum fluctuations. This latter data is in excellent agreement with the model of inflation, a theoretical primordial hyper-expansion of space that would have determined the distribution of all that energy and matter.
What is dark matter? What is dark energy? How to explain a quantum universe? In honoring Carlstrom, Ostriker, and Page, the 2015 Gruber Cosmology Prize recognizes science doing what science does best: answering fundamental questions while opening new frontiers for observers and theorists alike and raising new fundamental questions to puzzle us.Learn more >>
John Carlstrom to receive Gruber Cosmology Prize for experimental explorations of universe
June 11, 2015
The University of Chicago News
The 2015 Gruber Foundation Cosmology Prize has honored the University of Chicago's John E. Carlstrom, alumnus Jeremiah P. Ostriker, PhD'64, and Princeton University's Lyman Page for their individual and collective contributions to the study of the universe on the largest scales.
The 2015 prize is divided into two parts: half to a distinguished theorist, and the other half to two exceptional experimentalists. The theorist is Ostriker, a professor emeritus at Princeton University, now teaching at Columbia University. Ostriker, whose graduate school mentor was UChicago Nobel laureate Subrahmanyan Chandrasekhar, is being honored for his groundbreaking body of work over a five-decade career.
Carlstrom, the S. Chandrasekhar Distinguished Service Professor in Astronomy & Astrophysics, and Page, the Henry De Wolf Smyth Professor of Physics, have each overseen ground-based experiments that have provided a wealth of information about the origins and evolution of the universe. Carlstrom has worked extensively to study the cosmic microwave background, the relic radiation from the infancy of the universe, using the South Pole Telescope and other instruments.
"Together, the theoretical and experimental work of these three scientists has contributed to, clarified and advanced today's standard cosmological model," the Gruber Foundation wrote in announcing this year's prize.
Ostriker will receive half of the $500,000 award, while Carlstrom and Page will divide the other half. All three also will receive a gold medal Aug. 3 at the XXIX General Assembly of the International Astronomical Union in Honolulu, Hawaii.
Previous recipients of the Gruber Prize include Wendy Freedman, the University Professor in Astronomy & Astrophysics, who received the 2009 prize "for the definitive measurement of the rate of expansion of the universe, Hubble's Constant." One of the foremost awards in the field of cosmology, the prize honors "a leading cosmologist, astronomer, astrophysicist or scientific philosopher for theoretical, analytical, conceptual or observational discoveries leading to fundamental advances in our understanding of the universe," according to the Gruber Foundation.
Stephan Meyer, professor in astronomy & astrophysics, received a share of the prize in 2006 as a member of the Cosmic Background Explorer Team "for studies confirming that our universe was born in a hot Big Bang." He repeated the feat in 2012 as a member of the Wilkinson Microwave Anistropy Probe, which was honored for "exquisite measurements of anisotropies in the relic radiation from the Big Bang - the Cosmic Microwave Background."Learn more >>
MIRA and marathons
June 18, 2015
For three Argonne employees it's all about speed - both in and out of the lab.
Katrin Heitmann, a joint staff member in the High Energy Physics and Math and Computer Sciences Divisions; Salman Habib, senior physicist in the High Energy Physics and Math and Computer Sciences Divisions and Steve Rangel, lab appointee and Ph.D. student at Northwestern University have run the largest cosmological simulation on MIRA - one of the world's fastest supercomputers. Their aim was to create high-resolution simulations what would allow scientists to connect numerous surveys of the universe that measure the distribution of galaxies.
"Dealing with data is a big challenge in and of itself. What a large computer like MIRA enables is a lot of statistics." - Katrin Heitmann, Staff Member HEP and MCS
MIRA is capable of 10 quadrillion calculations per second. Located at the Argonne Leadership Computing Facility, it can do in one day what it would take the average personal computer 20 years to complete.
MIRA is also what brought Heitmann and Habib to Argonne from Los Alamos National Laboratory in Los Alamos, New Mexico.
Rangel joined the team soon after their move to Argonne. He said he first became interested in data science and data analysis when he was pursuing his master's degree. Later, his interest evolved into a passion for high performance computing.
"It was sort of a natural fit to come here and work with Salman and Katrin's group." - Steve Rangel, Ph.D. student at Northwestern University
The team has now begun to analyze the simulations, measuring galaxy distribution from a theory standpoint and comparing that data to observations of the universe. The team worked together to transform data from the MIRA simulation into an image that closely resembles the actual universe. Argonne joint staff member Nan Li and University of Chicago Professor Mike Gladders constructed the final visualization.
But besides performing the world's biggest simulation on MIRA, the team will put their own speed to the test later this year when they run the Bank of America Chicago Marathon.
The team ran together for the first time in this year's Bank of America Shamrock Shuffle, held March 29 in downtown Chicago. Rangel then suggested they run a marathon.
"At first I said, 'No way!'" Heitmann said. "Then, I got to thinking about it and thought it would be kind of cool if our group did it together. But I said we should at least do it for something more meaningful than just suffering for 26 miles."
With that idea in mind, Heitmann said she searched for charities listed on the Chicago Marathon website for which people can run. There, she found Chicago HOPES for Kids.
HOPES began in 2006 as an initiative of the Chicago Public Schools Department of Education Support for Students in Temporary Living Situations, or STLS. The organization collaborates with schools and shelters to establish after-school tutoring programs and provides students with additional support outside the classroom despite the challenges of homelessness, according to their website.
Heitmann and Habib will be running the marathon as part of the organization's team Hustle for Hopes. The money raised is used to purchase educational materials for the students.
"I like to support something local, that I can actually go see the students and meet with these people," Heitmann said.
Rangel will be running with the Chicago Area Runners Association (CARA) Road Scholars - a mentorship-based running program for at-risk Chicago area high school students. Mentors train students to successfully complete a half-marathon. The program also uses running to teach at-risk youth lessons in commitment, dedication and discipline, according to the CARA website. Funds raised by the marathon participants will be used to provide teens in the program with running shoes, transportation to training sites and cover race entry fees.
"I was lucky enough to start running when I was a kid," Rangel said. "For me, it really hits home."
The 26.2-mile marathon is scheduled to be held October 11 in downtown Chicago.Learn more >>
Chicago blues and the science in sound
June 19, 2015
The University of Chicago News Office
'Science and Sound' Preview Video
Everyone knows about visualizing data, but few have heard of sonifying data. Nevertheless, sound has great potential for organizing, interpreting and sharing scientific knowledge. Sound can also be a powerful tool to learn more about culture and the natural world.
Citing microbial bebop, Chicago blues, cosmic sound and a string quartet inspired by DNA's double helix, panelists at a program called "Science and Sound" on June 3 made a strong case for exploring and exploiting sound as a tool in scientific endeavors.
The occasion was the 11th in a series of joint speaker events for faculty at the University of Chicago as well as scientists, researchers and engineers at Argonne National Laboratory and Fermi National Accelerator Laboratory. It was held at Buddy Guy's Legends, the "cathedral" of Chicago blues and the "perfect place to discuss how sound serves science, pervades our lives and influences our emotions," said Donald Levy, vice president for Research and for National Laboratories at the University of Chicago.
Panelist Peter Larsen, assistant computational biologist at Argonne, explained how an algorithm he calls microbial bebop generates data into music by normalizing the data to a dynamic range of integer values and mapping those values to notes and chords. "I doubt that I'll ever come up with a composition that will change my understanding of microbial ecology, but the very exercise of doing this has already accomplished that," he said. "My job is to think of interesting ways to analyze big data... and microbial bebop has helped me find and understand better approaches to understanding data."
Another panelist, however, decided not to transcribe data directly into music, realizing that such an approach would not create an effective, cohesive composition. In composing "Helix Spirals" for string quartet, Grammy-winning composer Augusta Read Thomas, University Professor of Composition, approached the project metaphorically. She found inspiration in science and showed how well music can present an abstract and intellectual expression of nature.
"Helix Spirals" celebrates the Meselson-Stahl DNA replication experiment of 1958. The first movement, Thomas explained, portrays loci, that is, specific but "flickering" locations of genes or DNA sequences on a chromosome. The second movement portrays DNA replication with different instruments representing different strands. And the third conveys the beauty, richness and force of life.
"Nature is a great teacher of transformation, connections and, for me, music composition," said Thomas, who is now working on a piece about protein folding.
Indeed, music and sound is a "metaphor for the regularity of nature and even the movement of the heavens," said moderator Sidney Nagel, the Stein-Freiler Distinguished Service Professor in Physics.
Listening to learn
Instead of using science to generate or inspire music, panelist Michael Dietler, professor in anthropology, works the other way around. He listens to music to better understand cultures. "Music is a socially patterned, cultural phenomenon, and the blues has a lot to teach us about Chicago's African American culture," he said. Noting that many students spend four years on campus without exploring what Chicago has to offer, Dietler created a course on the history of the blues, which he called an enormously influential form of music.
"It's one thing to listen to the blues and quite another to understand how it evolved, impacts people, influences culture and continues to develop today," Dietler said. The difference is akin, he added, to the difference between enjoying the sound of French and actually understanding what is being said, idiomatically, historically and culturally.
Meanwhile, one of the best ways to learn about the universe is to listen to it. "Just like you can learn a lot about an instrument by studying the frequency of the sound it makes, you can learn a lot about the content of the universe by studying the Cosmic Microwave Background," said Bradford Benson, associate scientist and Wilson fellow at Fermilab and assistant professor in astronomy and astrophysics at the University of Chicago.
Cosmic Microwave Background is radiation left over from the Big Bang. "As we map the sky, we can detect sound waves from the early history of the universe, more than 13 billion years ago," Benson said. "When we measure the Cosmic Microwave Background's power spectrum - analogous to what you might do with a stereo amplifier - we find a remarkable harmonic structure," Benson said.
Overall, the panelists agreed that sound and science go well together, whether it is to listen to the cosmos - and each other - or to utilize sound as a tool to understand data and present knowledge, directly or indirectly. For instance, although microbial bebop is not an effective way to share data, it is a great way to engage students in science, Larsen has found. But the day may come when sonified data and audible pie charts are as commonplace as visual maps.
"We have to learn how to create and interpret charts, Venn diagrams, and other visual presentations of data," Dietler said. "Likewise, we could learn how to utilize sound and music more in science. We're used to conducting many things visually, but there's no reason why we couldn't handle more things audibly."
"Some of what we learn is communicated through sound, but there's a big potential to tap sound in new ways to achieve much more," Nagel concluded.Learn more >>
The Fabric of the Universe
July 15, 2015
Benedikt Diemer (Ph.D candidate, Astronomy & Astrophysics, UChicago); Isaac Facio (MFA candidate, Fiber & Material Studies, SAIC)
Faculty Advisors: Andrey Kravtsov (Astronomy & Astrophysics, UChicago); Helen Maria Nugent (Designed Objects (AIADO), SAIC)
The Fabric of the Universe is an investigation into a novel way of visualizing the structure of the universe: using 3-dimensional textiles. Isaac Facio and Benedikt Diemer will transform the shapes formed by the dark matter in large computer simulations into fabric using digital textile manufacturing technologies. The properties of the fabric, such as its opacity, will represent the properties of dark matter structures, such as their density. Ultimately, the textile will take shape in a large-scale sculpture of the dark matter filaments and nodes in the universe, known as the "cosmic web".
Funded by the Graduate Division, School of the Art Institute of Chicago (SAIC).Learn more >>
August 3, 2015
A year and half ago, physicists working with one of the world's odder scientific instruments scored a bittersweet breakthrough. The massive IceCube particle detector - a 3D array of 5160 light sensors buried kilometers deep in ice at the South Pole - spotted ghostly subatomic particles called neutrinos from beyond our galaxy (Science, 22 November 2013, p. 920). Researchers had previously detected lower energy neutrinos gushing from the sun and raining down from particle interactions in the atmosphere. But - except for a burp from a nearby supernova explosion in 1987 - neutrinos from the far reaches of the cosmos had eluded capture.
The discovery is Nobel-caliber stuff, some physicists say, but it also sounded a cautionary note. IceCube saw only about a dozen cosmic neutrinos per year. At that meager rate, the $279 million detector might never spot enough of them to work as advertised: as a neutrino telescope that could open up a whole new view of the heavens.
But as the data continue to come in, researchers are optimistic. After all, the fact that cosmic neutrinos have been spotted means that a big enough detector should be able to harvest enough of them to study the sky, says Francis Halzen, a theoretical physicist at the University of Wisconsin, Madison, and the driving force behind IceCube. "We see the flux, and now we have to figure out what it takes to do astronomy with it," he says. Halzen and his team are pushing to expand IceCube, which already fills a volume of a cubic kilometer. Meanwhile, other researchers have developed approaches that they say could be cheaper and more efficient.
More important, cosmic neutrinos are already telling a story, especially when combined with other particles from space: highly energetic photons called gamma rays, and ultrahigh-energy cosmic rays - protons and heavier atomic nuclei that reach energies a million times higher than humans have achieved with particle accelerators. Physicists have long wondered where in the universe the most energetic neutrinos, gamma rays, and cosmic rays are born. Now, in a tantalizing convergence, all three questions appear to share the same answer, says Olga Botner, a physicist and IceCube team member from Uppsala University in Sweden. "We believe that the engines that generate the cosmic rays also generate the gamma rays and neutrinos," she says.
If so, physicists have only one mystery to solve. The convergence also suggests the solution won't require exotic new particle physics: The conventional astrophysics of stars and galaxies should suffice.
AS TRACERS of the heavens, neutrinos offer many advantages over other particles from space. Electrically charged cosmic rays swirl in galactic magnetic fields; gamma rays tangle with radiation lingering from the big bang - the cosmic microwave background (CMB). Uncharged neutrinos, by contrast, zoom straight from their sources through almost everything the universe throws at them. "Neutrinos are the ultimate high-energy messenger," says Abigail Vieregg, a physicist at the University of Chicago in Illinois. "They're perfect - if you can see them."Learn more >>
Turner on Physics Nobel: Research Showing Neutrinos Have Mass Awarded Nobel Prize
October 8, 2015
Here and Now
October 6, 2015 at the Swedish Academy of Sciences in Stockholm, Sweden. Takaaki Kajita of Japan and Canada's Arthur B. McDonald won the Nobel Physics Prize for work on neutrinos. (Jonathan Nackstrand/AFP/Getty Images)
Looks like John Updike's poem about neutrinos being mass-less objects, "Cosmic Gall," might need an update.
Takaaki Kajita of Japan and Arthur McDonald of Canada have been awarded the Nobel Prize in Physics for their discovery that the subatomic particles called neutrinos do have mass. Scientists have called this a historic and major discovery.
Michael Turner, director of the Kavli Institute for Cosmological Physics at the University of Chicago, tells Here & Now's Jeremy Hobson how this discovery has changed scientists' understanding of the universe.
"The universe has so many neutrinos that they contribute as much to the mass budget of the universe as do the stars we see in the sky," Turner said.
He says the neutrino, which he affectionately calls a "lightweight," may be able to tell us about the origins of matter.
"The atoms that you and I are made out of, we believe that neutrinos in the early universe had a role in creating the ordinary matter that we're made out of," Turner said.
Correction: After our interview aired, Professor Turner sent us this correction: "It is now four Nobels for the neutrino: 1988 for the discovery of the muon neutrino; 1995 for the discovery of the neutrino itself; 2002 for solar and supernova neutrinos; and 2015 for neutrino mass. What a particle!"
Guest: Michael Turner, director of the Kavli Institute for Cosmological Physics at the University of Chicago.Learn more >>
Eckhardt Research Center to begin new phase of ambitious science
October 29, 2015
The University of Chicago News Office
The appetite for discovery at the new William Eckhardt Research Center was articulated by the University of Chicago’s very first Nobel laureate, astrophysicist Albert A. Michelson. "If a poet could at the same time be a physicist, he might convey to others the pleasure, the satisfaction, almost the reverence, which the subject inspires," Michelson wrote in his 1903 book Light Waves and Their Uses.
The Eckhardt Research Center enables precision science of many kinds, encompassing engineering in the quantum realm as well as studies of distant planets and cosmic evolution. In this sense too it carries on the spirit of Michelson, whose studies of light influenced microscopy as well as astronomy.
On Oct. 29 the UChicago community is celebrating the dedication of the Eckhardt Research Center, named for Chicago futures trader and alumnus William Eckhardt, SM'70, in recognition of his generous philanthropy to the sciences at the University of Chicago. The center is home to the Institute for Molecular Engineering and several sections of the Physical Sciences Division, including the Department of Astronomy and Astrophysics and the Kavli Institute for Cosmological Physics.
"We are excited that the William Eckhardt Research Center provides a sophisticated and beautiful home to support our distinctive programs in molecular engineering and astrophysics," said Provost Eric Isaacs. "IME has been successful in building a new model for molecular-level research with broad impact, and this facility will allow for even more ambitious work. Equally significant, this building befits the Department of Astronomy and Astrophysics long tradition of scientific eminence, and its continuing importance in that field of study."
The construction project was a collaboration of HOK, an architecture firm that specializes in the design of science and technology buildings, and Jamie Carpenter, an artist, sculptor, and architect known for his innovative work with light and glass.
The structure will be equipped with high-performance laboratories that will allow researchers to translate quantum information science into new technologies, develop instruments that can detect planets orbiting distant stars, and much more.
"We will find Earth-like planets and maybe signs of life from these planets," says Angela Olinto, the Homer J. Livingston Professor and chair of Astronomy and Astrophysics. "We will explore the most extreme events of the universe and try to explain what causes these events. We will study the first stars in the first galaxies ever assembled in the universe. We will also probe the most fundamental forces of the universe in the first tiny fraction of a second after the Big Bang."
Sharing the Eckhardt Center holds particular potential for new collaborations and interactions among scholars in the Institute for Molecular Engineering and the Physical Sciences.
"We will really span activities from the tiniest to the most gigantic," said Dean Matthew Tirrell, the founding Pritzker Director of IME and Argonne National Laboratory's deputy director for science. "Molecular engineering can contribute to astronomy and astrophysics via fabrication of new detectors and other instrumentation."
Fostering partnerships and interactions
One of the unique aspects of the Eckhardt Research Center is the Pritzker Nanofabrication Facility. Located in the first basement of the center, the innovative facility will allow for fabricating new features and devices at the nanoscale level, supporting IME's goal to solve societal issues with molecular-sized tools and solutions.
The nanofabrication lab "provides a unique research and development environment for the academic and industrial scientist interested in pursuing state-of-the-art micro- and nanoscale fabrication," says Andrew Cleland, the John A. MacLean Sr. Professor for Molecular Engineering Innovation and Enterprise, who will lead the facility. "We anticipate drawing researchers from the Chicago area, the Midwest, and nationally, both to use this facility and to establish collaborations with IME and UChicago researchers."
The breadth of scholarship at the Eckhardt Research Center is a good match for the Kavli Institute, which explores the profound connections between physics at the smallest and largest of scales - from quarks to the cosmos - with a focus on dark matter, dark energy, and how the universe began. The Kavli Institute will collaborate with IME researchers to create detectors for instruments that will make the most precise measurements of the cosmic microwave background - the microwave echo of the Big Bang.
"To recruit top faculty and top students requires the facilities to allow them to do the best science they can do," says Rocky Kolb, dean of the Physical Sciences Division and the Arthur Holly Compton Distinguished Service Professor of Astronomy and Astrophysics. "With the Eckhardt Research Center, we will have the facilities and the infrastructure that will allow our faculty and students to explore the cosmos - in ways they have never been able to before."
Exploring new fields and pushing boundaries
The center will create the first dedicated home for IME since it was created in 2011 in partnership with Argonne. Having all IME researchers in the same location, with diverse backgrounds ranging from chemical engineering to engineering physics to biomedical engineering, will be beneficial for future partnerships within IME itself, Tirrell said.
The idea of pushing research frontiers that cross disciplinary boundaries has permeated the Department of Astronomy and Astrophysics, the Kavli Institute, and the Institute of Molecular Engineering for years.
"We have, in astronomy, a reputation of being an innovative department that does new things," says Kolb. "We were the first department to do astrophysics. Particle cosmology really was developed here. It's part of our nature to explore new fields and transcend boundaries."
- Story includes material that first appeared on the Institute for Molecular Engineering website.Learn more >>
New ultra-sensitive instrument aims to detect hints of elusive dark matter particles
November 11, 2015
The University of Chicago News Office
There is five times more dark matter in the universe than "normal" matter - the atoms and molecules that make up the familiar world. Yet, it is still unknown what this dominant dark component actually is. On Nov. 11 an international collaboration of scientists inaugurated the new XENON1T instrument designed to search for dark matter with unprecedented sensitivity at the Gran Sasso Underground Laboratory in Italy.
Dark matter is one of the basic ingredients of the universe, and searches to detect it in laboratory-based experiments have been conducted for decades. However, until today dark matter has been observed only indirectly, via its gravitational interactions that govern the dynamics of the cosmos at all length-scales. It is expected that dark matter is made of a new, stable elementary particle that has escaped detection so far.
"We expect that several tens of thousands of dark matter particles per second are passing through the area of a thumbnail," said Luca Grandi, a UChicago assistant professor in physics and a member of the Kavli Institute for Cosmological Physics. "The fact that we did not detect them yet tells us that their probability to interact with the atoms of our detector is very small, and that we need more sensitive instruments to find the rare signature of this particle."
Grandi is a member of the XENON Collaboration, which consists of 21 research groups from the United States, Germany, Italy, Switzerland, Portugal, France, the Netherlands, Israel, Sweden and the United Arab Emirates. The collaboration's inauguration event took place Nov. 11 at the Laboratori Nazionali del Gran Sasso, one of the largest underground laboratories in the world.
"We need to put our experiment deep underground, using about 1,400 meters of solid rock to shield it from cosmic rays," said Grandi, who participated in the inauguration along with guests from funding agencies as well as journalists and colleagues. About 80 visitors joined the ceremony at the laboratory's experimental site, which measures 110 meters long, 15 meters wide and 15 meters high.
There, the new instrument is installed inside a 10-meter-diameter water shield to protect it from radioactive background radiation that originates from the environment. During introductory presentations, Elena Aprile, Columbia University professor and founder of the XENON project, illustrated the evolution of the program. It began with a 3 kilogram detector 15 years ago. The present-day instrument has a total mass of 3,500 kilograms.
Fighting against radioactivity
XENON1T employs the ultra-pure noble gas xenon as dark matter detection material, cooled down to -95 degrees Celsius to make it liquid.
"In order to see the rare interactions of a dark matter particle in your detector, you need to build an instrument with a large mass and an extremely low radioactive background," said Grandi.
"Otherwise you will have no chance to find the right events within the background signals."
For this reason, the XENON scientists have carefully selected all materials used in the construction of the detector, ensuring that their intrinsic contamination with radioactive isotopes meet the low-background experiment’s requirement.
"One has to realize that objects without any radioactivity do not exist," Grandi explained. "Minute traces of impurities are present in everything, from simple things like metal slabs to the walls of the laboratory to the human body. We are trying to reduce and control these radioactive contaminants as much as possible."
The XENON scientists measure tiny flashes of light and charge to reconstruct the position of the particle interaction within their detector, as well as the deposited energy and whether it might be induced by a dark matter particle or not. The light is observed by 248 sensitive photosensors, capable of detecting even single photons. A vacuum-insulated double-wall cryostat, resembling a gigantic version of a thermos flask, contains the cryogenic xenon and the dark matter detector.
The xenon gas is cooled and purified from impurities in the three-story XENON building, an installation with a transparent glass facade next to the water shield, which allows visitors to view the scientists inside. A gigantic stainless-steel sphere equipped with pipes and valves is installed on the ground floor.
"It can accommodate 7.6 tons of xenon in liquid and gaseous form," said Aprile. "This is more than two times the capacity we need for XENON1T, as we want to be prepared to swiftly increase the sensitivity of the experiment with a larger mass detector in the near future."
Aiming for a dark matter detection
Once fully operational, XENON1T will be the most sensitive dark matter experiment in the world. Grandi's group has been deeply involved in the preparation and assembly of the xenon Time Projection Chamber, the core of the detector. His group is also in charge for the development of the U.S. computing center for XENON1T data analysis via the UChicago Research Computing Center, directed by Birali Runesha, in close cooperation with Robert Gardner and his team at the Computation Institute.
In addition to Columbia's Aprile, leading the other six U.S. institutions are Ethan Brown, Rensselaer Polytechnic Institute; Petr Chaguine, Rice University; Rafael Lang, Purdue University; Kaixuan Ni, University of California, San Diego; and Hanguo Wang, University of California, Los Angeles.
XEON1T's first results are expected in early 2016. The collaboration expects the instrument to achieve most of its objectives within two years of data collection. The researchers then will move their project into a new phase.
"Of course we want to detect the dark matter particle," Grandi said, "but even if we have only found some hints after two years, we are in an excellent position to move on as we are already now preparing the next step of the project, which will be the far more sensitive XENONnT."Learn more >>