KICP in the News
Chicago Ideas Week: "Space Exploration: What's After The Final Frontier?"
chicagoideas.com, May 23, 2017
Reach for the stars with some of the country's leading astronomers. Human beings have wondered about the universe for centuries, but it is only within the last 70 years that we've begun venturing into space. Should we continue that effort? How are experts working towards the next era of space exploration? From NASA to private enterprises to citizen scientists, find out humanity's next frontier of space exploration.
What Does the Universe Actually Look Like?
Humans can only see a small spectrum of wavelengths, but the universe contains much more than we can actually see. Angela Olinto, chair of the department of astronomy at the University of Chicago, is working to bridge that gap.
Homer J. Livingston Distinguished Service Professor; Department of Astronomy and Astrophysics, University of Chicago
Angela Olinto is the Homer J. Livingston Distinguished Service Professor and chair of the department of astronomy and astrophysics at the University of Chicago. Olinto received her B.S. from PUC, Rio de Janeiro, and her Ph.D. from MIT. She has made significant contributions to a number of topics in astrophysics and is the PI of the EUSO-SPB mission (Extreme Universe Space Observatory on a Super-Pressure Balloon) and a member of the Pierre Auger Observatory, both designed to discover the origin of the highest energy cosmic rays.
Astrophysics and Unlocking the Universe
When it comes to scientific discover on how the universe works, what we know is just as important as what we thought we knew. Rocky Kolb and Hakeem Oluseyi sit down to discuss the most compelling research in quantum physics going on today.
Dean of Physical Sciences, University of Chicago
Edward W. Kolb (known to most as Rocky) is the Arthur Holly Compton Distinguished Service Professor of Astronomy & Astrophysics and the Dean of the Physical Sciences at the University of Chicago, as well as a member of the Enrico Fermi Institute and the Kavli Institute for Cosmological Physics. In 1983, he was a founding head of the Theoretical Astrophysics Group and in 2004 the founding Director of the Particle Astrophysics Center at Fermi National Accelerator Laboratory in Batavia, Illinois.
Kolb is a Fellow of the American Academy of Arts and Sciences and a Fellow of the American Physical Society. He was the recipient of the 2003 Oersted Medal of the American Association of Physics Teachers for notable contributions to the teaching of physics, the 1993 Quantrell Prize for teaching excellence at the University of Chicago and the 2009 Excellence in Teaching Award from the Graham School of the University of Chicago. His book for the general public, "Blind Watchers of the Sky," received the 1996 Emme Award of the American Aeronautical Society.
The field of Rocky's research is the application of elementary-particle physics to the very early Universe. In addition to over 200 scientific papers, he is a co-author of "The Early Universe," the standard textbook on particle physics and cosmology.
KICP Members: Edward W. Kolb; Angela V. Olinto
Scientific projects: Pierre Auger Observatory (AUGER)
World's most sensitive dark matter detector releases first results
UChicago News, May 18, 2017
Scientists behind XENON1T, the largest dark matter experiment of its kind ever built, are encouraged by early results, describing them as the best so far in the search for dark matter.
Dark matter is one of the basic constituents of the universe, five times more abundant than ordinary matter. Several astronomical measurements have corroborated the existence of dark matter, leading to an international effort to observe it directly. Scientists are trying to detect dark matter particle interacting with ordinary matter through the use of extremely sensitive detectors. Such interactions are so feeble that they have escaped direct detection to date, forcing scientists to build detectors that are more and more sensitive and have extremely low levels of radioactivity.
On May 18, the XENON Collaboration released results from a first, 30-day run of XENON1T, showing the detector has a record low radioactivity level, many orders of magnitude below surrounding material on earth.
"The care that we put into every single detail of the new detector is finally paying back," said Luca Grandi, assistant professor in physics at the University of Chicago and member of the XENON Collaboration. "We have excellent discovery potential in the years to come because of the huge dimension of XENON1T and its incredibly low background. These early results already are allowing us to explore regions never explored before."
The XENON Collaboration consists of 135 researchers from the United States, Germany, Italy, Switzerland, Portugal, France, the Netherlands, Israel, Sweden and the United Arab Emirates, who hope to one day confirm dark matter's existence and shed light on its mysterious properties.
Located deep below a mountain in central Italy, XENON1T features a 3.2-ton xenon dual-phase time projection chamber. This central detector sits fully submersed in the middle of the water tank, in order to shield it from natural radioactivity in the cavern. A cryostat helps keep the xenon at a temperature of minus-95 degrees Celsius without freezing the surrounding water. The mountain above the laboratory further shields the detector, preventing it from being perturbed by cosmic rays.
But shielding from the outer world is not enough, since all materials on Earth contain tiny traces of natural radioactivity. Thus extreme care was taken to find, select and process the materials making up the detector to achieve the lowest possible radioactive content. This allowed XENON1T to achieve record "silence" necessary to detect the very weak output of dark matter.
A particle interaction in the one-ton central core of the time projection chamber leads to tiny flashes of light. Scientists record and study these flashes to infer the position and the energy of the interacting particle -- and whether it might be dark matter.
Despite the brief 30-day science run, the sensitivity of XENON1T has already overcome that of any other experiment in the field probing unexplored dark matter territory.
"For the moment we do not see anything unexpected, so we set new constraints on dark matter properties," Grandi said. "But XENON1T just started its exciting journey and since the end of the 30-day science run, we have been steadily accumulating new data."
UChicago central to international collaboration
Grandi's group is very active within XENON1T, and it is contributing to several aspects of the program. After its initial involvement in the preparation, assembly and early operations of the liquid xenon chamber, the group shifted its focus in the last several months to the development of the computing infrastructure and to data analysis.
"Despite its low background, XENON1T is producing a large amount of data that needs to be continuously processed," said Evan Shockley, a graduate student working with Grandi. "The raw data from the detector are directly transferred from Gran Sasso Laboratory to the University of Chicago, serving as the unique distribution point for the entire collaboration."
The framework, developed in collaboration with a group led by Robert Gardner, senior fellow at the Computation Institute, allows for the processing of data, both on local and remote resources belonging to the Open Science Grid. The involvement of UChicago's Research Computing Center including Director Birali Runesha allows members of the collaboration all around the world to access processed data for high-level analyses.
Grandi's group also has been heavily involved in the analysis that led to this first result. Christopher Tunnell, a fellow at the Kavli Institute for Cosmological Physics, is one of the two XENON1T analysis coordinators and corresponding author of the result. Recently, UChicago hosted about 25 researchers for a month to perform the analyses that led to the first results.
"It has been a large, concentrated effort and seeing XENON1T back on the front line makes me forget the never-ending days spent next to my colleagues to look at plots and distributions," Tunnell said. "There is no better thrill than leading the way in our knowledge of dark matter for the coming years."
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KICP Members: Luca Grandi; Christopher Tunnell
KICP Students: Katrina Miller; Evan Shockley; Nickolas Upole
Scientific projects: XENON1T
Prof. Angela Olinto participates in Arts Summit 2017
Washington Post, May 8, 2017
by Anne Midgette, Washington Post
The Kennedy Center Arts Summit is an annual spring convening designed to bring thought leaders from the arts and related fields together for conversation and connection. The 2017 edition of the Summit examined how arts and culture play a critical role in shaping society, especially through interdisciplinary connections.
The program serves as a reflection on current and past efforts as well as the launching pad for new collaborations and initiatives among participants.
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KICP Members: Angela V. Olinto
Michael Turner has been elected to American Philosophical Society
UChicago News, May 4, 2017
Three UChicago faculty members have been elected to the American Philosophical Society, the oldest learned society in the United States.
They are Lorraine Daston, visiting professor in the John U. Nef Committee on Social Thought; Neil H. Shubin, the Robert R. Bensley Distinguished Service Professor of Organismal Biology and Anatomy; and Michael S. Turner, the Bruce V. and Diana M. Rauner Distinguished Service Professor.
Michael S. Turner is a theoretical cosmologist who helped to pioneer the interdisciplinary field that combines particle astrophysics and cosmology. His research focuses on the earliest moments of creation, and he has made seminal contributions to theories surrounding dark matter, dark energy and inflation. A former chair of UChicago's Department of Astronomy & Astrophysics, Turner currently serves as director of the Kavli Institute for Cosmological Physics.
Turner chaired the National Research Council's Committee on the Physics of the Universe, which published the influential report, "Connecting Quarks with the Cosmos." He previously served as assistant director for mathematical and physical sciences at the National Science Foundation, the chief scientist of Argonne National Laboratory and the president of the American Physical Society.
Turner is a member of the National Academy of Sciences and the American Academy of Arts and Sciences. He has received numerous honors, including the 2010 Dannie Heineman Prize for pioneering cosmological physics research from the American Astronomical Society and the American Institute of Physics, and was selected by the University of Chicago to deliver the 2013 Ryerson Lecture.
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KICP Members: Michael S. Turner
Gary Steigman, Who Teased Out the Universe's Dark Secrets, Dies at 76
The New York Times, April 28, 2017
by Dennis Overbye, The New York Times
Gary Steigman, an astronomer whose pioneering studies of the Big Bang helped show that most of the matter in the universe was not made of atoms - a finding that led to the modern conception of a universe awash in dark matter being pushed into an infinite night by dark energy - died on April 9 in Columbus, Ohio. He was 76.
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A Cosmic-Ray Hunter Takes to the Sky
Quanta Magazine, April 28, 2017
Angela Olinto's new balloon experiment takes her one step closer to the unknown source of the most energetic particles in the universe.
In April 25, at 10:50 a.m. local time, a white helium balloon ascended from Wanaka, New Zealand, and lifted Angela Olinto's hopes into the stratosphere. The football stadium-size NASA balloon, now floating 20 miles above the Earth, carries a one-ton detector that Olinto helped design and see off the ground. Every moonless night for the next few months, it will peer out at the dark curve of the Earth, hunting for the fluorescent streaks of mystery particles called ''ultrahigh-energy cosmic rays'' crashing into the sky. The Extreme Universe Space Observatory Super Pressure Balloon (EUSO-SPB) experiment will be the first ever to record the ultraviolet light from these rare events by looking down at the atmosphere instead of up. The wider field of view will allow it to detect the streaks at a faster rate than previous, ground-based experiments, which Olinto hopes will be the key to finally figuring out the particles' origin.
Olinto, the leader of the seven-country EUSO-SPB experiment, is a professor of astrophysics at the University of Chicago. She grew up in Brazil and recalls that during her ''beach days in Rio'' she often wondered about nature. Over the 40 years since she was 16, Olinto said, she has remained captivated by the combined power of mathematics and experiments to explain the universe. ''Many people think of physics as hard; I find it so elegant, and so simple compared to literature, which is really amazing, but it's so varied that it's infinite,'' she said. ''We have four forces of nature, and everything can be done mathematically. Nobody's opinions matter, which I like very much!''
Olinto has spent the last 22 years theorizing about ultrahigh-energy cosmic rays. Composed of single protons or heavier atomic nuclei, they pack within quantum proportions as much energy as baseballs or bowling balls, and hurtle through space many millions of times more energetically than particles at the Large Hadron Collider, the world's most powerful accelerator. ''They're so energetic that theorists like me have a hard time coming up with something in nature that could reach those energies,'' Olinto said. ''If we didn't observe these cosmic rays, we wouldn't believe they actually would be produced.''
Olinto and her collaborators have proposed that ultrahigh-energy cosmic rays could be emitted by newly born, rapidly rotating neutron stars, called "pulsars.'' She calls these ''the little guys,'' since their main competitors are ''the big guys'': the supermassive black holes that churn at the centers of active galaxies. But no one knows which theory is right, or if it's something else entirely. Ultrahigh-energy cosmic rays pepper Earth so sparsely and haphazardly - their paths skewed by the galaxy's magnetic field - that they leave few clues about their origin. In recent years, a hazy ''hot spot'' of the particles coming from a region in the Northern sky seems to be showing up in data collected by the Telescope Array in Utah. But this potential clue has only compounded the puzzle: Somehow, the alleged hot spot doesn't spill over at all into the field of view of the much larger and more powerful Pierre Auger Observatory in Argentina.
To find out the origin of ultrahigh-energy cosmic rays, Olinto and her colleagues need enough data to produce a map of where in the sky the particles come from - a map that can be compared with the locations of known cosmological objects. ''In the cosmic ray world, the big dream is to point,'' she said during an interview at a January meeting of the American Physical Society in Washington, D.C.
She sees the current balloon flight as a necessary next step. If successful, it will serve as a proof of principle for future space-based ultrahigh-energy cosmic-ray experiments, such as her proposed satellite detector, Poemma (Probe of Extreme Multi-Messenger Astrophysics). While in New Zealand in late March preparing for the balloon launch, Olinto received the good news from NASA that Poemma had been selected for further study.
Olinto wants answers, and she has an ambitious timeline for getting them. An edited and condensed version of our conversations in Washington and on a phone call to New Zealand follows.
QUANTA MAGAZINE: What was your path to astrophysics and ultrahigh-energy cosmic rays?
ANGELA OLINTO: I was really interested in the basic workings of nature: Why three families of quarks? What is the unified theory of everything? But I realized how many easier questions we have in astrophysics: that you could actually take a lifetime and go answer them. Graduate school at MIT showed me the way to astrophysics - how it can be an amazing route to many questions, including how the universe looks, how it functions, and even particle physics questions. I didn't plan to study ultrahigh-energy cosmic rays; but every step it was, ''OK, it looks promising.''
QUANTA MAGAZINE: How long have you been trying to answer this particular question?
ANGELA OLINTO: In 1995, we had a study group at Fermilab for ultrahigh-energy cosmic rays, because the AGASA (Akeno Giant Air Shower Array) experiment was seeing these amazing events that were so energetic that the particles broke a predicted energy limit known as the ''GZK cutoff.'' I was studying magnetic fields at the time, and so Jim Cronin, who just passed away last year in August - he was a brilliant man, charismatic, full of energy, lovely man - he asked that I explain what we know about cosmic magnetic fields. At that time the answer was not very much, but I gave him what we did know. And because he invited me I got to learn what he was up to. And I thought, wow, this is pretty interesting.
QUANTA MAGAZINE: Later you helped plan and run Pierre Auger, an array of detectors spread across 3,000 square kilometers of Argentinian grassland. Did you actually go around and persuade farmers to let you put detectors on their land?
ANGELA OLINTO: Not me; it was the Argentinian team who did the amazing job of talking to everybody. The American team helped build a planetarium and a school in that area, so we did interact with them, but not directly on negotiations over land. In Argentina it was like this: You get a big fraction of folks who are very excited and part of it from the beginning. Gradually you got through the big landowners. But eventually we had a couple who were really not interested. So we had two regions in the middle of the array that were empty of the detectors for quite some time, and then we finally closed it.
Space is much easier in that sense; it's one instrument and no one owns the atmosphere. On the other hand, the nice thing about having all the farmers involved is that Malargue, the city in Argentina that has had the detectors deployed, has changed completely. The students are much more connected to the world and speak English. Some are coming to the U.S. for undergraduate and even graduate school eventually. It's been a major transformation for a small town where nobody went to college before. So that was pretty amazing. It took a huge outreach effort and a lot of time, but this was very important, because we needed them to let us in.
QUANTA MAGAZINE: Why is space the next step?
ANGELA OLINTO: To go the next step on the ground - to get 30,000 square kilometers instrumented - is something I tried to do, but it's really difficult. It's hard enough with 3,000; it was crazy to begin with, but we did it. To get to the next order of magnitude seems really difficult. On the other hand, going to space you can see 100 times more volume of air in the same minute. And then we can increase by orders of magnitude the ability to see ultrahigh-energy cosmic rays, see where they are coming from, how they are produced, what objects can reach these kinds of energies.
QUANTA MAGAZINE: What will we learn from EUSO-SPB?
ANGELA OLINTO: We will not have enough data to revolutionize our understanding at this point, but we will show how it can be done from space. The work we do with the balloon is really in preparation for something like Poemma, our proposed satellite experiment. We plan to have two telescopes free-flying and communicating with each other, and by recording cosmic-ray events with both of the them we should be able to also reproduce the direction and composition very precisely.
QUANTA MAGAZINE: Speaking of Poemma, do you still teach a class called Cosmology for Poets?
ANGELA OLINTO: We don't call it that anymore, but yes. What it entails is teaching nonscience majors what we know about the history of the universe: what we've learned and why we think it is the way it is, how we measure things and how our scientific understanding of the history of the universe is now pretty interesting. First, we have a story that works brilliantly, and second, we have all kinds of puzzles like dark matter and dark energy that are yet to be understood. So it gives the sense of the huge progress since I started looking at this. It's unbelievable; in my lifetime it's changed completely, and mostly due to amazing detections and observations.
One thing I try to do in this course is to mix in some art. I tell them to go to a museum and choose an object or art piece that tells you something about the universe - that connects to what we talked about in class. And here my goal is to just make them dream a bit free from all the boundaries of science. In science there's right and wrong, but in art there are no easy right and wrong answers. I want them to see if they can have a personal attachment to the story I told them. And I think art helps me do that.
QUANTA MAGAZINE: You’ve said that when you left Brazil for MIT at 21, you were suffering from a serious muscle disease called polymyositis, which also recurred in 2006. Did those experiences contribute to your drive to push the field forward?
ANGELA OLINTO: I think this helps me not get worked up about small stuff. There are always many reasons to give up when working on high-risk research. I see some colleagues who get worked up about things that I'm like, whatever, let's just keep going. And I think that attitude to minimize things that are not that big has to do with being close to death. Being that close, it's like, well, everything is positive. I'm very much a positive person and most of the time say, let's keep pushing. I think having a question that is not answered that is well posed is a very good incentive to keep moving.
QUANTA MAGAZINE: Between the ''big guys'' and the ''little guys'' - black holes versus pulsating neutron stars - what's your bet for which ones produce ultrahigh-energy cosmic rays?
ANGELA OLINTO: I think it's 50-50 at this point - both can do it and there's no showstopper on either side - but I root always for the underdog. It looks like ultrahigh-energy cosmic rays have a heavier composition, which helps the neutron star case, since we had heavy elements in our neutron star models from the beginning. However, it's possible that supermassive black holes do the job, too, and basically folks just imagine that the bigger the better, so the supermassive black holes are usually a little bit ahead. It could be somewhere in the middle: intermediate-mass black holes. Or ultrahigh-energy cosmic rays could be related to other interesting phenomena, like fast radio bursts, or something that we don't know anything about.
QUANTA MAGAZINE: When do you think we'll know for sure?
ANGELA OLINTO: You know how when you climb the mountain - I rarely look at where I'm going. I look at the next two steps. I know I'm going to the top but I don't look at the top, because it's difficult to do small steps when the road is really long. So I don't try to predict exactly. But I would imagine - we have a decadal survey process, so that takes quite some time, and then we have another decade - so let's say, in the 2030s we should know the answer.
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KICP Members: Angela V. Olinto
Scientific projects: Pierre Auger Observatory (AUGER)
Prof. Angela Olinto hopes telescope will help unravel mysteries of cosmic rays
UChicago News, April 25, 2017
UChicago-led NASA balloon mission launches, with goal of breaking flight record
NASA on April 24 launched a football-stadium-sized, super-pressure balloon on a mission that aims to set a record for flight duration while carrying a telescope that scientists at the University of Chicago and around the world will use to study cosmic rays.
Researchers from 16 nations hope the balloon, which lifted off from an airfield in Wanaka, New Zealand, will stay afloat for up to 100 days as it travels at 110,000 feet around the Southern Hemisphere. From its vantage point in near-space, the telescope is designed to detect ultra-high energy cosmic rays as they penetrate the Earth's atmosphere. An ultraviolet camera on the telescope will take 400,000 images a second as it looks back toward Earth to try and capture some of the particles.
"The mission is searching for the most energetic cosmic particles ever observed," said Angela V. Olinto, the Homer J. Livingston Distinguished Service Professor at the University of Chicago and principal investigator of the project, known as the Extreme Universe Space Observatory on a Super Pressure Balloon (EUSO-SPB). "The origin of these particles is a great mystery that we'd like to solve. Do they come from massive black holes at the center of galaxies? Tiny, fast-spinning stars? Or somewhere else?"
The next step for Olinto and her fellow scientists is a space mission, now being designed by NASA centers under her leadership, to observe a greater atmospheric area for detecting high-energy cosmic rays and neutrinos. These extremely rare particles hit the atmosphere at a rate of only one per square kilometer per century.
As the NASA balloon travels around the Earth in the coming months, it may be visible from the ground, particularly at sunrise and sunset, to those who live in the mid-latitudes of the Southern Hemisphere such as Australia, Argentina and South Africa.
The complex balloon launch depended on the right weather conditions on the surface of the Earth all the way up to 110,000 feet, where the balloon travels. The launch window for lift-off opened March 25, and it a full month until the 18.8-million-cubic-foot balloon could take flight. Scientists now hope the balloon, made of a polyethylene film stronger and more durable than the type used in sandwich bags, can break the previous flight record of 46 days, set in 2016.
At a relatively low cost, NASA's heavy-lift balloons have become critical launch vehicles for testing new technologies and science instruments to assure success for costlier, higher-risk spaceflight missions, said Debbie Fairbrother, chief of NASA's Balloon Program Office.
"For decades, balloons have provided access to the near-space environment to support scientific investigations, technology testing, education and workforce development," Fairbrother said. "We're thrilled to provide this high-altitude flight opportunity for EUSO-SPB as they work to validate their technologies while conducting some really mind-blowing science."
Balloons also are part of UChicago's storied history of cosmic ray research, which dates to 1928 when Nobel laureate Robert Millikan first coined the term in a research paper. Pierre Auger, the namesake of the cosmic ray observatory in Argentina, launched hot air balloon experiments in the 1940s from the former site of Stagg Field. UChicago scientists used balloons in the Arctic Circle to discover positrons (the anti-particles of electrons) in the 1960s.
The EUSO-SPB project includes two UChicago undergraduates, Leo Allen and Mikhail Rezazadeh, who built an infrared camera under the supervision of Olinto and Stephan Meyer, professor of astronomy and astrophysics, to observe the cloud coverage at night.
Sixteen countries were involved with the design of the telescope and construction involved the U.S., France, Italy, Germany, Poland, Mexico and Japan. The U.S. team, funded by NASA, is led by UChicago, with co-investigators at Colorado School of Mines, Marshall Space Flight Center, University of Alabama at Huntsville and Lehman College at the City University of New York.
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KICP Members: Stephan S. Meyer; Angela V. Olinto
KICP Students: Leo Allen; Mikhail Rezazadeh
Virtual Earth-sized telescope aims to capture first image of a black hole
UChicago News, April 21, 2017
UChicago-led South Pole Telescope part of international effort to study event horizon
A powerful network of telescopes around the Earth is attempting to create the first image of a black hole, an elusive gravitational sinkhole that Albert Einstein first predicted in 1915.
The UChicago-led South Pole Telescope is part of the Event Horizon Telescope, which combines eight observatories in six locations to create a virtual Earth-sized telescope so powerful it could spot a nickel on the surface of the moon. Scientists spent ten days in April gathering data on Sagittarius A*, a black hole at the center of the Milky Way, as well as a supermassive black hole about 1,500 times heavier at the center of galaxy M87.
Each radio-wave observatory collected so much data that it could not be transmitted electronically. Instead, it was downloaded onto more than 1,000 hard drives and flown to the project's data analysis centers at the MIT Haystack Observatory in Westford, Mass., and the Max Planck Institute for Radio Astronomy in Bonn, Germany.
Over the next year, supercomputers will correlate, combine and interpret the data using very long baseline interferometry, a procedure common in astronomy but never implemented on such an enormous scale. The goal is to produce an image of the event horizon, the boundary of a black hole where luminous gases burn at tens of millions of degrees and from which nothing escapes, not even light.
"It all came together for us: telescopes with higher resolutions, better experiments, more computer power, bright ideas, good weather conditions and so on," said John Carlstrom, the Subramanyan Chandrasekhar Distinguished Service Professor of Astronomy and Astrophysics at UChicago, who leads the South Pole Telescope collaboration. "I'm very confident that we'll come up with not only a good image, but a better understanding of black holes and gravity."
The telescopes in the network employ radio dishes that can detect very short wavelengths, even less than a millimeter -- the shorter the wavelength, the higher the resolution. Water, dust and clouds of gas can block radio waves, so the telescopes in Event Horizon were selected, in part, for being located in deserts, dry plateaus and mountaintops. Nevertheless, a storm or high winds could have ruined data collection.
Astronomers have taken aim at black holes before, but the big difference this time comes from incorporating the new Atacama Large Millimeter/submillimeter Array and the South Pole Telescope into the virtual network. Located high in the mountains of Chile, ALMA is the most complex astronomical observatory ever built, using 66 high-precision dish antennas with a total collecting area of more than 71,000 square feet. The South Pole Telescope provides the critical north-south resolving power to pick apart the details of Sagittarius A*.
"ALMA is the key to this experiment," Carlstrom said. "It gives us great sensitivity and at the incredibly short wavelength of 1.3 millimeters. But next year we'll repeat this experiment at 0.8 millimeters to get an even higher resolution.
"We'll always be pushing the limits," he added.
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KICP Members: John E. Carlstrom
Scientific projects: South Pole Telescope (SPT)
Researchers Provide New Insight Into Dark Matter Halos
University of Pennsylvania, April 19, 2017
Many scientists now believe that more than 80 percent of the matter of the universe is locked away in mysterious, as yet undetected, particles of dark matter, which affect everything from how objects move within a galaxy to how galaxies and galaxy clusters clump together in the first place.
This dark matter extends far beyond the reach of the furthest stars in the galaxy, forming what scientists call a dark matter halo. While stars within the galaxy all rotate in a neat, organized disk, these dark matter particles are like a swarm of bees, moving chaotically in random directions, which keeps them puffed up to balance the inward pull of gravity.
Bhuvnesh Jain, a physics professor in Penn's School of Arts & Sciences, and postdoc Eric Baxter are conducting research that could give new insights into the structure of these halos.
The researchers wanted to investigate whether these dark matter halos have an edge or boundary.
"People have generally imagined a pretty smooth transition from the matter bound to the galaxy to the matter between galaxies, which is also gravitationally attracted to the galaxies and clusters," Jain said. "But theoretically, using computer simulations a few years ago, researchers at the University of Chicago showed that for galaxy clusters a sharp boundary is expected, providing a distinct transition that we should be able to see through a careful analysis of the data."
Using a galaxy survey called the Sloan Digital Sky Survey, or SDSS, Baxter and Jain looked at the distribution of galaxies around clusters. They formed a team of experts at the University of Chicago and other institutions around the world to examine thousands of galaxy clusters. Using statistical tools to do a joint analysis of several million galaxies around them, they found a drop at the edge of the cluster. Baxter and collaborator Chihway Chang at the University of Chicago led a paper reporting the findings, accepted for publication in the Astrophysical Journal.
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KICP Members: Chihway Chang; Andrey V. Kravtsov; Surhud More
KICP Students: Eric J. Baxter; Benedikt Diemer
Scientific projects: SDSS Supernova Survey (SDSS SS); Sloan Digital Sky Survey (SDSS)
NASA to launch telescope on super-pressure balloon in search for cosmic rays
UChicago News, April 6, 2017
Prof. Angela Olinto leads project to collect data at near-space altitudes
The National Aeronautics and Space Administration is preparing to use a super-pressure balloon to launch into near space a pioneering telescope designed to detect ultra-high-energy cosmic rays as they interact with the Earth's atmosphere.
"We're searching for the most energetic cosmic particles that we’ve ever observed," said Angela V. Olinto, the Homer J. Livingston Distinguished Service Professor at the University of Chicago and principal investigator of the project, known as the Extreme Universe Space Observatory-Super Pressure Balloon. "The origin of these particles is a great mystery that we'd like to solve. Do they come from massive black holes at the center of galaxies? Tiny, fast-spinning stars? Or somewhere else?"
The extremely rare particles hit the atmosphere at a rate of only one per square kilometer per century. To assure that it will capture some of the particles, the telescope's camera takes 400,000 images a second as it casts a wide view back toward the Earth.
Preparations are complete in Wanaka, New Zealand for the balloon's launch, which will happen as soon as scientists and engineers have the right weather conditions. Researchers hope the balloon will stay afloat for up to 100 days, thereby setting a record for an ultra-long duration flight.
NASA describes the super-pressure balloon as the "most persnickety" of all the flight and launch vehicles it operates. Launching the balloon depends on just the right weather conditions on the surface of the Earth all the way up to 110,000 feet, where the balloon travels.
The project will set the stage for a space mission currently being planned. "That would enlarge even more the volume of the atmosphere that we can observe at one time," said Olinto, who serves as chair of UChicago's Department of Astronomy and Astrophysics. "We need to observe a significantly large number of these cosmic messengers to discover what are their sources and how they interact at their energetic extremes."
When an ultra-high-energy cosmic ray reaches the Earth's atmosphere, it induces a series of interactions that stimulates a large cosmic ray shower. The new telescope, which detects at night, will capture the ultra-violet fluorescence produced by the interaction of these particle showers with the nitrogen molecules in the air.
"High-energy cosmic rays have never been observed this way from space," said Lawrence Wiencke, professor of physics at the Colorado School of Mines and co-leader of the project. "This mission to a sub-orbital altitude is a pioneering opportunity for us. Our international collaboration is very excited about this launch and about the new data that will be collected along the way."
The project lends itself to participation by graduate and undergraduate students, Olinto said. Leo Allen and Mikhail Rezazadeh, two UChicago undergraduates, built an infrared camera under the supervision of UChicago Prof. Stephan Meyer and Olinto to observe the cloud coverage at night under EUSO-SPB.
Sixteen countries were involved with the design of the telescope. The U.S. team, funded by NASA, is led by UChicago, Colorado School of Mines, Marshall Space Flight Center, University of Alabama at Huntsville and Lehman College at the City University of New York.
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KICP Members: Stephan S. Meyer; Angela V. Olinto
KICP Students: Leo Allen; Mikhail Rezazadeh
A recharged debate over the speed of the expansion of the universe could lead to new physics
AAAS, March 8, 2017
It was the early 1990s, and the Carnegie Observatories in Pasadena, California, had emptied out for the Christmas holiday. Wendy Freedman was toiling alone in the library on an immense and thorny problem: the expansion rate of the universe.
Carnegie was hallowed ground for this sort of work. It was here, in 1929, that Edwin Hubble first clocked faraway galaxies flying away from the Milky Way, bobbing in the outward current of expanding space. The speed of that flow came to be called the Hubble constant.
Freedman's quiet work was soon interrupted when fellow Carnegie astronomer Allan Sandage stormed in. Sandage, Hubble's designated scientific heir, had spent decades refining the Hubble constant, and had consistently defended a slow rate of expansion. Freedman was the latest challenger to publish a faster rate, and Sandage had seen the heretical study.
"He was so angry," recalls Freedman, now at the University of Chicago in Illinois, "that you sort of become aware that you're the only two people in the building. I took a step back, and that was when I realized, oh boy, this was not the friendliest of fields."
The acrimony has diminished, but not by much. Sandage died in 2010, and by then most astronomers had converged on a Hubble constant in a narrow range. But in a twist Sandage himself might savor, new techniques suggest that the Hubble constant is 8% lower than a leading number. For nearly a century, astronomers have calculated it by meticulously measuring distances in the nearby universe and moving ever farther out. But lately, astrophysicists have measured the constant from the outside in, based on maps of the cosmic microwave background (CMB), the dappled afterglow of the big bang that is a backdrop to the rest of the visible universe. By making assumptions about how the push and pull of energy and matter in the universe have changed the rate of cosmic expansion since the microwave background was formed, the astrophysicists can take their map and adjust the Hubble constant to the present-day, local universe. The numbers should match. But they don't.
It could be that one approach has it wrong. The two sides are searching for flaws in their own methods and each other's alike, and senior figures like Freedman are racing to publish their own measures. "We don't know which way this is going to land," Freedman says.
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KICP Members: Wendy L. Freedman; Daniel Scolnic
New World-Leading Limit on Dark Matter Search from PICO Experiment
SNOLAB News, February 27, 2017
The PICO Collaboration is excited to announce that the PICO-60 dark matter bubble chamber experiment has produced a new dark matter limit after analysis of data from the most recent run. This new result is a factor of 17 improvement in the limit for spin-dependent WIMP-proton cross-section over the already world-leading limits from PICO-2L run-2 and PICO-60 CF3I run-1 in 2016.
The PICO-60 experiment is currently the world's largest bubble chamber in operation; it is filled with 52 kg of C3F8 (octafluoropropane) and is taking data in the ladder lab area of SNOLAB. The detector uses the target fluid in a superheated state such that a dark matter particle interaction with a fluorine nucleus causes the fluid to boil and creates a tell tale bubble in the chamber.
The PICO experiment uses digital cameras to see the bubbles and acoustic pickups to improve the ability to distinguish between dark matter particles and other sources when analysing the data.
The superheated detector technology has been at the forefront of spin-dependent (SD) searches, using various refrigerant targets including CF3I, C4F10 and C2ClF5, and two primary types of detectors: bubble chambers and droplet detectors. PICO is the leading experiment in the direct detection of dark matter for spin-dependent couplings and is developing a much larger version of the experiment with up to 500 kg of active mass.
The PICO Collaboration would like to acknowledge the support of the National Sciences and Engineering Research Council of Canada (NSERC) and the Canada Foundation for Innovation (CFI) for funding.
This work was also supported by the U.S. Department of Energy Office of Science and the US National Science Foundation under Grants PHY-1242637, PHY-0919526, PHY-1205987 and PHY-1506377, and in part by the Kavli Institute for Cosmological Physics at the University of Chicago through grant PHY-1125897, and an endowment from the Kavli Foundation and its founder Fred Kavli.
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KICP Members: Juan I. Collar
Scientific projects: COUPP/PICO
Kumiko Kotera: doing beautiful physics without giving up on family, art and the rest of the world
e-EPS, February 24, 2017
Kumiko Kotera is a young researcher in Astrophysics, at the Institut d'Astrophysique de Paris, (IAP) of the French Centre National de la Recherche Scientifique (CNRS). She builds theoretical models to probe the most violent phenomena in the Universe, by deciphering their so-called "astroparticle" messengers (cosmic rays, neutrinos and photons). Today, she is one of the leaders of the international project GRAND (Giant Radio Array for Neutrino Detection), that aims at detecting very-high energy cosmic neutrinos. In 2016, she received a prestigious award: the CNRS bronze medal for her important achievements.
Lucia Di Ciaccio: Do you have any female 'physicist cult figure' or 'role model'?
Kumiko Kotera: Angela Olinto, professor at the University of Chicago, is undoubtedly my mentor. She struggled to build her brilliant career at a time when female physicists were far more isolated than today and opened the path for all of us. She showed me how one can be strong, respected, and do beautiful physics without ever giving up on kindness, family, art, and the rest of the world.
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KICP Members: Angela V. Olinto
Abigail Vieregg has been awarded a Sloan Research Fellowship
The University of Chicago News Office, February 21, 2017
Five UChicago faculty members have earned 2017 Sloan Research Fellowships: Bryan Dickinson, assistant professor of chemistry; Suriyanarayanan Vaikuntanathan, assistant professor of chemistry; Joseph Vavra, associate professor of economics at the University of Chicago Booth School of Business; Abigail Vieregg, assistant professor of physics; and Alessandra Voena, associate professor of economics.
Abigail Vieregg is interested in answering questions about the nature of the universe at its highest energies through experimental work in particle astrophysics and cosmology. In particle astrophysics, she focuses on searching for the highest energy neutrinos that come from the most energetic sources in the universe. In cosmology, Vieregg works with a suite of telescopes at the South Pole to help determine what happened during the first moments after the Big Bang by measuring the polarization of the cosmic microwave background.
Vieregg was a NASA Earth and Space Sciences Graduate Fellow at UCLA and a National Science Foundation Office of Polar Programs Postdoctoral Fellow at the Harvard-Smithsonian Center for Astrophysics.
Vieregg joined the UChicago faculty in 2014.
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KICP Members: Abigail G. Vieregg
Scientific projects: BICEP2/The Keck Array/BICEP3
Cosmos Controversy: The Universe Is Expanding, but How Fast?
The New York Times, February 21, 2017
by Dennis Overbye, The New York Times
A small discrepancy in the value of a long-sought number has fostered a debate about just how well we know the cosmos.
There is a crisis brewing in the cosmos, or perhaps in the community of cosmologists. The universe seems to be expanding too fast, some astronomers say. Recent measurements of the distances and velocities of faraway galaxies don't agree with a hard-won "standard model" of the cosmos that has prevailed for the past two decades. The latest result shows a 9 percent discrepancy in the value of a long-sought number called the Hubble constant, which describes how fast the universe is expanding. But in a measure of how precise cosmologists think their science has become, this small mismatch has fostered a debate about just how well we know the cosmos. "If it is real, we will learn new physics," said Wendy Freedman of the University of Chicago, who has spent most of her career charting the size and growth of the universe.
Michael S. Turner of the University of Chicago said, "If the discrepancy is real, this could be a disruption of the current highly successful standard model of cosmology and just what the younger generation wants - a chance for big discoveries, new insights and breakthroughs."
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KICP Members: Wendy L. Freedman; Daniel Scolnic; Michael S. Turner
Galactic X-rays could point to dark matter proof
BBC News, February 2, 2017
by Edwin Cartlidge, BBC News
KICP Senior Member Dan Hooper discusses a recent claim of the detection of the 3.5 keV X-ray line in our Galaxy with the BBC.
"The new paper claims a modest detection," said Dr Hooper, "but it doesn't sway me very strongly at this point."
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KICP Members: Daniel Hooper
Research reinforces role of supernovae in clocking the universe
UChicago News, January 4, 2017
How much light does a supernova shed on the history of universe?
New research by cosmologists at the University of Chicago and Wayne State University confirms the accuracy of Type Ia supernovae in measuring the pace at which the universe expands. The findings support a widely held theory that the expansion of the universe is accelerating and such acceleration is attributable to a mysterious force known as dark energy. The findings counter recent headlines that Type Ia supernova cannot be relied upon to measure the expansion of the universe.
Using light from an exploding star as bright as entire galaxies to determine cosmic distances led to the 2011 Nobel Prize in physics. The method relies on the assumption that, like lightbulbs of a known wattage, all Type Ia supernovae are thought to have nearly the same maximum brightness when they explode. Such consistency allows them to be used as beacons to measure the heavens. The weaker the light, the farther away the star. But the method has been challenged in recent years because of findings the light given off by Type Ia supernovae appears more inconsistent than expected.
"The data that we examined are indeed holding up against these claims of the demise of Type Ia supernovae as a tool for measuring the universe," said Daniel Scolnic, a postdoctoral scholar at UChicago's Kavli Institute for Cosmological Physics and co-author of the new research published in Monthly Notices of the Royal Astronomical Society. "We should not be persuaded by these other claims just because they got a lot of attention, though it is important to continue to question and strengthen our fundamental assumptions."
One of the latest criticisms of Type Ia supernovae for measurement concluded the brightness of these supernovae seems to be in two different subclasses, which could lead to problems when trying to measure distances. In the new research led by David Cinabro, a professor at Wayne State, Scolnic, Rick Kessler, a senior researcher at the Kavli Institute, and others, they did not find evidence of two subclasses of Type Ia supernovae in data examined from the Sloan Digital Sky Survey Supernovae Search and Supernova Legacy Survey. The recent papers challenging the effectiveness of Type Ia supernovae for measurement used different data sets.
A secondary criticism has focused on the way Type Ia supernovae are analyzed. When scientists found that distant Type Ia supernovae were fainter than expected, they concluded the universe is expanding at an accelerating rate. That acceleration is explained through dark energy, which scientists estimate makes up 70 percent of the universe. The enigmatic force pulls matter apart, keeping gravity from slowing down the expansion of the universe.
Yet a substance that makes up 70 percent of the universe but remains unknown is frustrating to a number of cosmologists. The result was a reevaluation of the mathematical tools used to analyze supernovae that gained attention in 2015 by arguing that Type Ia supernovae don't even show dark energy exists in the first place.
Scolnic and colleague Adam Riess, who won the 2011 Nobel Prices for the discovery of the accelerating universe, wrote an article for Scientific American Oct. 26, 2016, refuting the claims. They showed that even if the mathematical tools to analyze Type Ia supernovae are used "incorrectly," there is still a 99.7 percent chance the universe is accelerating.
The new findings are reassuring for researchers who use Type Ia supernovae to gain an increasingly precise understanding of dark energy, said Joshua A. Frieman, senior staff member at the Fermi National Accelerator Laboratory who was not involved in the research.
"The impact of this work will be to strengthen our confidence in using Type Ia supernovae as cosmological probes," he said.
Citation: "Search for Type Ia Supernova NUV-Optical Subclasses," by David Cinabro and Jake Miller (Wayne State University); and Daniel Scolnic and Ashley Li (Kavli Institute for Cosmological Physics at the University of Chicago); and Richard Kessler (Kavli Institute for Cosmological Physics at University of Chicago and the Department of Astronomy and Astrophysics at the University of Chicago). Monthly Notices of the Royal Astronomical Society, November 2016. DOI: 10.1093/mnras/stw3109"
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KICP Members: Joshua A. Frieman; Richard Kessler; Daniel Scolnic
Scientific projects: SDSS Supernova Survey (SDSS SS); Sloan Digital Sky Survey (SDSS)
Have Astronomers Decided Dark Energy Doesn't Exist?
Scientific American, October 26, 2016
No, they haven't, although plenty of recent headlines have suggested otherwise.
This week, a number of media outlets have put out headlines like "The universe is expanding at an accelerating rate, or is it?" and "The Universe Is Expanding But Not At An Accelerating Rate New Research Debunks Nobel Prize Theory." This excitement is due to a paper just published in Nature's Scientific Reports called "Marginal evidence for cosmic acceleration from Type Ia supernovae," by Nielsen, Guffanti and Sarkar.
Once you read the article, however, it's safe to say there is no need to revise our present understanding of the universe. All the paper does is slightly reduce our certainty in what we know - and then only by discarding most of the cosmological data on which our understanding is based. It also ignores important details in the data it does consider. And even if you leave aside these issues, the headlines are wrong anyway. The study concluded that we're now only 99.7 percent sure that the universe is accelerating, which is hardly the same as "it's not accelerating."
The initial discovery that the universe is expanding at an accelerating rate was made by two teams of astronomers in 1998 using Type Ia Supernovae as cosmic measuring tools. Supernovae -- exploding stars -- are some of the most powerful blasts in the entire cosmos, roughly equivalent to a billion-billion-billion atomic bombs exploding at once. Type Ia's are a special kind of supernova in that, unlike other supernovae, they all explode with just about the same luminosity every time likely due to a critical mass limit. This similarity means that the differences in their observed brightness are almost entirely based on how far away they are. This makes them ideal for measuring cosmic distances. Furthermore, these objects are relatively common, and they are so bright that we can see them billions of light years away. This shows us how the universe appeared billions of years ago, which we can compare to how it looks today.
These supernovae are often called "standard candles" for their consistency, but they're more accurately "standardizable candles," because in practice, their precision and accuracy can be improved still further by accounting for small differences in their explosions by observing how long the explosion takes to unfold and how the color of the supernovae are reddened by dust between them and us. Finding a way to do these corrections robustly was what led to the discovery of the accelerating universe.
The recent paper that has generated headlines used a catalog of Type Ia supernovae collected by the community (including us) which has been analyzed numerous times before. But the authors used a different method of implementing the corrections - and we believe this undercuts the accuracy of their results. They assume that the mean properties of supernovae from each of the samples used to measure the expansion history are the same, even though they have been shown to be different and past analyses have accounted for these differences. However, even ignoring these differences, the authors still find that there is roughly a 99.7 percent chance that the universe is accelerating - very different from what the headlines suggest.
Furthermore, the overwhelming confidence astronomers have that the universe is expanding faster now than it was billions of years ago is based on much more than just supernova measurements. These include tiny fluctuations in the pattern of relic heat after the Big Bang (i.e., the cosmic microwave background) and the modern day imprint of those fluctuations in the distribution of galaxies around us (called baryon acoustic oscillations). The present study also ignores the presence of a substantial amount of matter in the Universe, confirmed numerous times and ways since the 1970's, further reducing the study confidence. These other data show the universe to be accelerating independently from supernovae. If we combine the other observations with the supernova data, we go from 99.99 percent sure to 99.99999 percent sure. That's pretty sure!
We now know that dark energy, which is what we believe causes the expansion of the universe to accelerate, makes up 70 percent of the universe, with matter constituting the rest. The nature of dark energy is still one of the largest mysteries of all of astrophysics. But there has been no active debate about whether dark energy exists and none about whether the universe is accelerating since this picture was cemented a decade ago.
There are now many new large surveys, both on the ground and in space, whose top priority over the next two decades is to figure out exactly what this dark energy could be. For now, we have to continue to improve our measurements and question our assumptions. While this recent paper does not disprove any theories, it is still good for everyone to pause for a second and remember how big the questions are that we are asking, how we reached the conclusions we have to date and how seriously we need to test each building block of our understanding.
Dan Scolnic and Adam G. Riess
Dan Scolnic is a Hubble and KICP Fellow at The Kavli Institute For Cosmological Physics at The University of Chicago. He works on multiple surveys, including The Dark Energy Survey, Pan-STARRS, Foundation and WFIRST, to use Type Ia Supernovae to measure dark energy. Adam G. Riess is an astrophysicist at Johns Hopkins University and the Space Telescope Science Institute. His research on distant supernovae revealed that the expansion of the universe is accelerating, a discovery for which he shared the 2011 Nobel Prize in Physics.
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KICP Members: Daniel Scolnic
KICP member Daniel Holz discusses Gravitational Waves on PBS' The Good Stuff
The Good Stuff, October 13, 2016
In 2015 scientists working at the Laser Interferometer Gravitational-Wave observatory, or LIGO, detected gravitational waves for the first time. But how did they do it? What is a gravitational wave? And why is confirming something that Albert Einstein predicted a hundred years ago one of the greatest scientific achievements of the past century?
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KICP Members: Ben Farr; Daniel E. Holz
KICP Students: Hsin-Yu Chen; Zoheyr Doctor
Physics Confronts Its Heart of Darkness
Scientific American, September 1, 2016
Cracks are showing in the dominant explanation for dark matter. Is there anything more plausible to replace it?
Physics has missed a long-scheduled appointment with its future - again. The latest, most sensitive searches for the particles thought to make up dark matter - the invisible stuff that may comprise 85 percent of the mass in the cosmos - have found nothing. Called WIMPs (weakly interacting massive particles), these subatomic shrinking violets may simply be better at hiding than physicists thought when they first predicted them more than 30 years ago. Alternatively, they may not exist, which would mean that something is woefully amiss in the underpinnings of how we try to make sense of the universe. Many scientists still hold out hope that upgraded versions of the experiments looking for WIMPs will find them but others are taking a second look at conceptions of dark matter long deemed unlikely.
Whatever dark matter is, it is not accounted for in the Standard Model of particle physics, a thoroughly-tested "theory of almost everything" forged in the 1970s that explains all known particles and all known forces other than gravity. Find the identity of dark matter and you illuminate a new path forward to a deeper understanding of the universe - at least, that is what physicists hope.
WIMPs would get their gravitational heft from being somewhere between one and a thousand times the mass of a proton. Their sole remaining connection to our familiar world would be through the weak nuclear force, which is stronger than gravity but only active across tiny distances on the scale of atomic nuclei. If they exist, WIMPs should surround us like an invisible fog, their chances of interacting with ordinary matter so remote that one could pass through light-years of elemental lead unscathed.
Undaunted, experimentalists have spent decades devising and operating enough cleverly named WIMP detectors to overflow your average can of alphabet soup. (CDEX, CDMS, CoGeNT, COUPP and CRESST are just the most notable examples that start with the letter C.) The delicate work of detecting any weak, rare and fleeting interactions of WIMPs with atoms requires isolation and solitude, confining most detectors to caverns, abandoned mines and other outlier subterranean spaces.
One of the latest null results in the search for WIMPs came from the Large Underground Xenon (LUX) experiment, a third of a ton of liquid xenon held at a frosty -100 degrees Celsius inside a giant water-filled tank buried one and a half kilometers beneath the Black Hills of South Dakota. There, shielded from most sources of contaminating noise, researchers have spent more than a year's worth of time looking for flashes of light emanating from WIMPs striking xenon nuclei. On July 21 they announced they had seen none.
The next disappointment came on August 5 from the most powerful particle accelerator ever built: CERN's Large Hadron Collider (LHC) near Geneva, Switzerland. In 2012 after it found the Higgs boson - the Standard Modelâ€™s long-predicted final particle that imbues others with mass - many theorists believed the next blockbuster result from the LHC would be a discovery of how the Higgs (or other hypothesized particles very much like it) helps produce the WIMPs thought to suffuse the cosmos. Since spring 2015 the LHC has been pursuing these ideas by smashing protons together at unprecedentedly high energies at rates of up to a billion per second, pushing into new frontiers of particle physics. Early on, two independent teams had spied a telltale anomaly in the subatomic wreckage, an excess of energy from proton collisions that hinted at new physics perhaps produced by WIMPs (or, to be fair, many additional exotic possibilities). Instead, as the LHC smashed more protons and collected more data, the anomaly fizzled out, indicating it had been a statistical fluke.
Taken together, these two null results are a double-edged sword for dark matter. On one hand, their new constraints on the plausible masses and interactions of WIMPs are priming plans for next-generation detectors that could offer better chances of success. On the other, they have ruled out some of the simplest and most cherished WIMP models, raising fresh fears that the long-postulated particles might be a multidecadal detour in the search for dark matter.
Edward "Rocky" Kolb, a cosmologist now at the University of Chicago who in the 1970s helped lay the foundations for the generations of WIMP hunts to come, declared the 2010s "the decade of the WIMP" but now admits the search has not gone as planned. "We are now more in the dark about dark matter than we were five years ago," he says. So far, Kolb says, most theorists have responded by "letting a thousand WIMPs bloom," creating ever-more baroque and exotic theories to explain how WIMPs have managed to dodge all our detectors.
There is, of course, another possibility - that WIMPs are not the solution to dark matter we should be looking for. "WIMPs emerged as a simple, elegant, compelling explanation for a complex phenomenon," Kolb says. "And for every complex phenomenon there is a simple, elegant, compelling explanation that is wrong."
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KICP Members: Edward W. Kolb
James W. Cronin, Nobel laureate and pioneering physicist, 1931-2016
UChicago News, August 27, 2016
Scholar remembered for groundbreaking research on particle physics and cosmic rays
James W. Cronin, a pioneering scientist who shared the Nobel Prize in physics in 1980 for his groundbreaking work on the laws governing matter and antimatter and their role in the universe, died Aug. 25 in Saint Paul, Minn. He was 84.
Cronin, SM'53, PhD'55, spent much of his career at the University of Chicago, first as a student and then a professor. A University Professor Emeritus of Physics and Astronomy & Astrophysics, he was remembered this week as a mentor, collaborator and visionary.
"He inspired us all to reach further into the unknown with deep intuition, solid scientific backing and poetic vision," said Angela Olinto, the Homer J. Livingston Distinguished Service Professor in Astronomy and Astrophysics. "He accepted his many recognitions and accolades with so much humility that he encouraged many generations to follow his vision."
Edward "Rocky" Kolb, dean of the Physical Sciences Division and the Arthur Holly Compton Distinguished Service Professor in Astronomy and Astrophysics, described Cronin as â€śa person of real honesty and integrity who was a mentor and friend to so many people."
"Just like in basketball, there are good players in science, but the greatest players are the ones who make the people around them better. Jim was that great player," Kolb said.
Cronin's research that resulted in the Nobel Prize came in 1964 while he was working with Val Fitch at the Brookhaven National Laboratory. The two scientists, who were Princeton University professors at the time, observed the first example of nature's preference for matter over antimatter. Without the phenomenon, which physicists refer to as charge-parity violation, no matter would exist in the universe.
Cronin and Fitch studied the short-lived subatomic particles that appeared after the collision of accelerated protons and the nucleus of an atom. They observed indirect charge-parity violation, which is the unbalanced mixing of neutral subatomic kaon particles with their charged antiparticles. Called the Fitch-Cronin effect, the finding showed that some physical laws are violated when the direction of time is reversed. It also lent support for the big bang theory of the universe's origin.
Cronin later in his career shifted his focus, becoming co-leader of the Pierre Auger Project. The $50 million international collaboration of 250 scientists across 16 nations focused on the mysterious sources of rare but extremely powerful cosmic rays that periodically bombard Earth. The project led to the creation of the Auger Observatory, which consists of a vast array of cosmic-ray detectors in Argentina.
"It was 25 years ago since Jim and I first conceived the idea of what became the Auger Collaboration. It was definitely a great partnership as we drummed up financial and scientific support for the collaboration," said Alan Watson, emeritus professor of physics at the University of Leeds and a fellow of the Royal Society.
The collaboration has made definitive measurements on the energy spectrum of cosmic rays, on the patterns of their arrival directions, and on their mass compositions. It also has conducted particle physics research, measuring phenomena that far exceed the energies of the Large Hadron Collider.
"It's been an outstanding success, and it's still going strong," Watson said.
Drawing inspiration from Fermi
Cronin was born on Sept. 29, 1931, in Chicago, while his father was a graduate student in classical languages and literatures at the University of Chicago. The younger Cronin received a bachelor's from Southern Methodist University in 1951 before returning to the University of Chicago as a National Science Foundation Fellow to earn his master's and doctoral degrees.
Cronin met his first wife, Annette Martin, while both were students at the University. She died in 2005, and Cronin married Carol McDonald (nee Champlin) in late 2006.
Cronin began his scientific career at Brookhaven before becoming a member of the physics faculty at Princeton in 1958. In 1971, he joined the University of Chicago, where he was appointed the University Professor of Physics. He became University Professor Emeritus of Physics and Astronomy & Astrophysics in 1997.
Cronin shared a birthdate with Prof. Enrico Fermi, who earned the Nobel Prize in Physics in 1938. Cronin, who knew Fermi from his graduate school days at UChicago, organized a symposium in 2001 to mark the 100th anniversary of Fermi's birth, and was editor of the resulting book, Fermi Remembered. It included contributions from seven Nobel Prize recipients and many other scientists who studied under or worked with Fermi at UChicago.
"What's significant about Fermi is if you look through his career, he never just did the same thing. He kept moving on to new scientific challenges," Cronin once said of Fermi. The same statement also could be applied to Cronin and his research shift from high-energy physics to ultra-high-energy cosmic rays.
Cronin's honors include the University of Chicago Alumni Medal (2013), election as a foreign member of the Royal Society of London (2007), Distinguished Graduate Award of SMU's Dedman College (2004), Legion dâ€™honneur of France (2001), National Medal of Science (1999), University of Chicago's Quantrell Award for Excellence in Undergraduate Teaching (1994), Laureate of Lincoln Academy of Illinois (1981), Ernest Lawrence Memorial Award for outstanding contributions in the field of atomic energy (1977), John Price Wetherill Medal of the Franklin Institute (1975) and the Research Corporation Award (1968).
In 1990 Cronin delivered the Ryerson Lecture, which provides an opportunity each year for a distinguished faculty member to address the UChicago community on significant aspects of his or her research.
He was a member of the National Academy of Sciences, American Academy of Arts and Sciences, American Physical Society, American Philosophical Society, Accademia Nazionale dei Lincei of Italy, Mexican Academy of Sciences and the Russian Academy of Sciences. Cronin also had received honorary doctorates from l'Universite Pierre et Marie Curie, University of Leeds, Universite de Franche Conte, Novo Gorica Polytechnique of Slovenia, University of Nebraska, the University of Santiago de Compostela, the Colorado School of Mines, and the Karlsruhe Institute of Technology.. Cronin served as international chair of the College de France in 1999-2000.
Cronin is survived by his wife, Carol; daughter, Emily Grothe; son, Daniel Cronin; and six grandchildren: James, Cathryn, Caroline, Meredith, Alex and Marlo. A daughter, Cathryn Cranston, died in 2011.
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KICP Members: James W. Cronin; Edward W. Kolb; Angela V. Olinto
Scientific projects: Pierre Auger Observatory (AUGER)
Allusionist 41: Getting Toasty
theallusionist.org, August 22, 2016
When you choose to spend the winter in Antarctica, you'll be prepared for it to be cold. You know that nobody will be leaving or arriving until springtime. And you're braced for months of darkness. But a few weeks after the last sunset, you might find you can't even string a sentence together. And even if you can, that sentence may only make sense in Antarctica.
To explain why are Antarctica veteran Allison 'Sandwich' Barden, endocrinologist Tom Baranski, and astrophysicists Amy Lowitz and Christine Moran, reporting from the South Pole in the depths of winter.
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Scientific projects: South Pole Telescope (SPT)
The Particle That Wasn't
The New York Times, August 8, 2016
A great "might have been" for the universe, or at least for the people who study it, disappeared Friday.
Last December, two teams of physicists working at CERN's Large Hadron Collider reported that they might have seen traces of what could be a new fundamental constituent of nature, an elementary particle that is not part of the Standard Model that has ruled particle physics for the last half-century.
A bump on a graph signaling excess pairs of gamma rays was most likely a statistical fluke, they said. But physicists have been holding their breath ever since.
If real, the new particle would have opened a crack between the known and the unknown, affording a glimpse of quantum secrets undreamed of even by Einstein. Answers to questions like why there is matter but not antimatter in the universe, or the identity of the mysterious dark matter that provides the gravitational glue in the cosmos. In the few months after the announcement, 500 papers were written trying to interpret the meaning of the putative particle.
On Friday, physicists from the same two CERN teams reported that under the onslaught of more data, the possibility of a particle had melted away.
"We don't see anything," said Tiziano Camporesi of CERN, the European Organization for Nuclear Research and a spokesman for one of the detector teams known as C.M.S., on the eve of the announcement. "In fact, there is even a small deficit exactly at that point."
His statement was echoed by a member of the competing team, known as Atlas. James Beacham, of Ohio State University, said, "As it stands now, the bumplet has gone into a flatline."
The new results were presented in Chicago at the International Conference of High Energy Physics, ICHEP for short, by Bruno Lenzi of CERN for the Atlas team, and Chiara Rovelli for their competitors named for their own detector called C.M.S., short for Compact Muon Solenoid.
The presentations were part of an outpouring of dozens of papers from the two teams on the results so far this year from the collider, all of them in general agreement with the Standard Model.
The main news is that the collider, which had a rocky start, exploding back in 2008, is now running "swimmingly" in CERN's words, producing up to a billion proton-proton collisions a second.
"We're just at the beginning of the journey," said Fabiola Gianotti, CERNâ€™s director-general, in a statement.
Michael Turner, a cosmologist at the University of Chicago, said, "Energy is the great tool of discovery, so going from 8 TeV to 13 TeV is a really big deal. Keep your fingers crossed."
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KICP Members: Michael S. Turner
Angela Olinto received distinguished service professorship
UChicago News, July 21, 2016
Faculty members recognized with named, distinguished service professorships
Ten faculty members have received named professorships or have been named distinguished service professors. Luc Anselin, John R. Birge, John List and Angela Olinto received distinguished service professorships; and Ethan Bueno de Mesquita, Michael Franklin, Christopher Kennedy, Jason Merchant, Haresh Sapra and Nir Uriel received named professorships.
Angela Olinto has been named the Homer J. Livingston Distinguished Service Professor in Astronomy & Astrophysics and the College.
Olinto has made important contributions to the physics of quark stars, inflationary theory, cosmic magnetic fields and particle astrophysics. Her research interests span theoretical astrophysics, particle and nuclear astrophysics, and cosmology. She has focused much of her recent work on understanding the origins of the highest-energy cosmic rays and neutrinos.
Olinto is an elected fellow of the American Association for the Advancement of Science for her distinguished contributions to the field of astrophysics, particularly exotic states of matter and extremely high-energy cosmic ray studies at the Pierre Auger Observatory in Argentina. She now leads the International collaboration of the Extreme Universe Space Observatory mission that will fly in a NASA super pressure balloon in 2017 and will be first to observe tracks of ultra-energy particles from above.
She also is a fellow of the American Physical Society and has received the Chaire dâ€™Excellence Award of the French Agence Nationale de Recherche. Olinto has received the Llewellyn John and Harriet Manchester Quantrell Award for Excellence in Undergraduate Teaching, as well as the Faculty Award for Excellence in Graduate Teaching and Mentoring.
Olinto joined the UChicago faculty in 1996.
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KICP Members: Angela V. Olinto
Angela Olinto: the 114th Congress Hearing - Astronomy, Astrophysics, and Astrobiology
Committee on Science, Space and Technology, 114th Congress, July 12, 2016
Joint Space Subcommittee and Research and Technology Subcommittee Hearing - Astronomy, Astrophysics, and Astrobiology
Tuesday, July 12, 2016 - 10:00am
- Space Subcommittee Chairman Brian Babin (R-Texas)
- Research and Technology Subcommittee Chairwoman Barbara Comstock (R-Va.)
- Chairman Lamar Smith (R-Texas)
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KICP Members: Angela V. Olinto
Simulations foresee hordes of colliding black holes in observatory's future
UChicago News, June 28, 2016
New calculations predict that the Laser Interferometer Gravitational wave Observatory (LIGO) will detect approximately 1,000 mergers of massive black holes annually once it achieves full sensitivity early next decade.
The prediction, published online June 22 in the journal Nature, is based on computer simulations of more than a billion evolving binary stars. The simulations are based on state-of-the-art modeling of the physics involved, informed by the most recent astronomical and astrophysical observations.
"The main thing we find is that what LIGO detected makes sense," said Daniel Holz, associate professor in physics and astronomy at the University of Chicago and a co-author of the Nature paper. The simulations predict the formation of black-hole binary stars in a range of masses that includes the two already observed. As more LIGO data become available, Holz and his colleagues will be able to test their results more rigorously.
The paper's lead author, Krzysztof Belczynski of Warsaw University in Poland, said he hopes the results will surprise him, that they will expose flaws in the work. Their calculations show, for example, that once LIGO reaches full sensitivity, it will detect only one pair of colliding neutron stars for every 1,000 detections of the far more massive black-hole collisions.
"Actually, I would love to be proven wrong on this issue. Then we will learn a lot," Belczynski said.
Forming big black holes
The new Nature paper, which includes co-authors Tomasz Bulik of Warsaw University and Richard O'Shaughnessy of the Rochester Institute of Technology, describes the most likely black-hole formation scenario that generated the first LIGO gravitational-wave detection in September 2015. That detection confirmed a major prediction of Albert Einstein's 1915 general theory of relativity.
The paper is the most recent in a series of publications, topping a decade of analyses where Holz, Belczynski and their associates theorize that the universe has produced many black-hole binaries in the mass range that are close enough to Earth for LIGO to detect.
"Here we simulate binary stars, how they evolve, turn into black holes and eventually get close enough to crash into each other and make gravitational waves that we would observe," Holz said.
The simulations show that the formation and evolution of a typical system of binary stars results in a merger of similar masses, and after similarly elapsed times, to the event that LIGO detected last September. These black hole mergers have masses ranging from 20 to 80 times more than the sun.
LIGO will begin recording more gravitational-wave-generating events as the system becomes more sensitive and operates for longer periods of time. LIGO will go through successive upgrades over the coming years, and is expected to reach its design sensitivity by 2020. By then, the Nature study predicts that LIGO might be detecting more than 100 black hole collisions annually.
LIGO has detected big black holes and big collisions, with a combined mass greater than 30 times that of the sun. These can only be formed out of big stars.
"To make those you need to have low metallicity stars, which just means that these stars have to be relatively pristine," Holz said. The Big Bang produced mainly hydrogen and helium, which eventually collapsed into stars.
As these stars burned they forged heavier elements, which astronomers call "metals." Those stars with fewer metals lose less mass as they burn, resulting in the formation of more massive black holes when they die. That most likely happened approximately two billion years after the Big Bang, before the young universe had time to form significant quantities of heavy metals. Most of those black holes would have merged relatively quickly after their formation.
LIGO would be unable to detect the ones that merged early and quickly. But if the binaries were formed in large enough numbers, a small fraction would survive for longer periods and would end up merging 11 billion years after the Big Bang (2.8 billion years ago), recently enough for LIGO to detect.
"That's in fact what we think happened," Holz said. Statistically speaking, "it's the most likely scenario." He added, however, that the universe continues to produce binary stars in local, still pristine pockets of low metallicity that resemble conditions of the early universe.
"In those pockets you can make these big stars, make the binaries, and then they'll merge right away and we would detect those as well."
Belczynski, Holz and collaborators have based their simulations on what they regard as the best models available. They assume "isolated formation," which involves two stars forming in a binary, evolving in tandem into black holes, and eventually merging with a burst of gravitational wave emission. A competing model is "dynamical formation," which focuses on regions of the galaxy that contain a high density of independently evolving stars. Eventually, many of them will find each other and form binaries.
"There are dynamical processes by which those black holes get closer and closer and eventually merge," Holz said. Identifying which black holes merged under which scenario is difficult. One potential method would entail examining the black holes' relative spins. Binary stars that evolved dynamically are expected to have randomly aligned spins; detecting a preference for aligned spins would be clear evidence in favor of the isolated evolutionary model.
LIGO is not yet able to precisely measure black hole spin alignment, "but we're starting to get there," Holz said. "This study represents the first steps in the birth of the entirely new field of gravitational wave astronomy. We have been waiting for a century, and the future has finally arrived."
Citation: "The first gravitational-wave source from the isolated evolution of two stars in the 40-100 solar mass range," by Krzysztof Belczynski, Daniel E. Holz, Tomasz Bulik, and Richard Oâ€™Shaughnessy," Nature, Vol. 534, pp. 512-515, June 23, 2016, doi:10.1038/nature18322.
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KICP Members: Daniel E. Holz
Gravitational waves detected from second pair of colliding black holes
UChicago News, June 16, 2016
At 9:38:53 CST on Dec. 25, 2015, scientists observed gravitational waves - ripples in the fabric of spacetime - for the second time.
The gravitational waves were detected by both of the twin Laser Interferometer Gravitational-Wave Observatory detectors, located in Livingston, La., and Hanford, Wash. University of Chicago scientists led by Daniel Holz, assistant professor in physics and astronomy, are members of the LIGO collaboration.
The LIGO observatories are funded by the National Science Foundation, and were conceived, built and are operated by the California Institute of Technology and the Massachusetts Institute of Technology. The discovery, accepted for publication in the journal Physical Review Letters, was made by the LIGO Scientific Collaboration and the Virgo Collaboration using data from the two LIGO detectors.
The LIGO detectors operated for approximately four months late last year, yielding about 50 days of data. An analysis of the first 16 days of data yielded the event that the LIGO Collaboration announced in February 2016.
Black holes events
"Now weâ€™ve analyzed the rest of the data, and we have another event thatâ€™s particularly interesting," Holz said. "It's not quite as loud as the first one, but it's quite beautiful in its own way. The event is composed of smaller black holes, and at least one is spinning. This marks the official turning point from 'detector' to 'observatory.'"
Gravitational waves carry information about their origins and about the nature of gravity that cannot otherwise be obtained, and physicists have concluded that these gravitational waves were produced during the final moments of the merger of two black holes - 14 and 8 times the mass of the sun - to produce a single, more massive spinning black hole that is 21 times the mass of the sun.
"It is very significant that these black holes were much less massive than those observed in the first detection," said Gabriela Gonzalez, LIGO Scientific Collaboration spokesperson and professor of physics and astronomy at Louisiana State University. "Because of their lighter masses compared to the first detection, they spent more time - about one second - in the sensitive band of the detectors. It is a promising start to mapping the populations of black holes in our universe."
During the merger, which occurred approximately 1.4 billion years ago, a quantity of energy roughly equivalent to the mass of the sun was converted into gravitational waves. The detected signal comes from the last 27 orbits of the black holes before their merger. Based on the arrival time of the signals - with the Livingston detector measuring the waves 1.1 milliseconds before the Hanford detector - the position of the source in the sky can be roughly determined.
The first detection of gravitational waves, announced on Feb. 11, 2016, was a milestone in physics and astronomy: It confirmed a major prediction of Albert Einstein's 1915 general theory of relativity, and marked the beginning of the new field of gravitational wave astronomy.
Both discoveries were made possible by the enhanced capabilities of Advanced LIGO, a major upgrade that increases the sensitivity of the instruments compared to the first-generation LIGO detectors, enabling a large increase in the volume of the universe probed.
'With the advent of Advanced LIGO, we anticipated researchers would eventually succeed at detecting unexpected phenomena, but these two detections thus far have surpassed our expectations,' said NSF Director France A. Cordova. "NSF's 40-year investment in this foundational research is already yielding new information about the nature of the dark universe."
Advanced LIGO's next data-taking run will begin this fall. By then, further improvements in detector sensitivity are expected to allow LIGO to reach as much as 1.5 to 2 times more of the volume of the universe. The Virgo detector is expected to join in the latter half of the coming observing run.
LIGO research is carried out by the LIGO Scientific Collaboration, a group of more than 1,000 scientists from universities around the United States and in 14 other countries. More than 90 universities and research institutes in the LSC develop detector technology and analyze data; approximately 250 students are strong contributing members of the collaboration. Virgo research is carried out by the Virgo Collaboration, consisting of more than 250 physicists and engineers belonging to 19 different European research groups.
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KICP Members: Daniel E. Holz