KICP in the News, 2017



 
Research reinforces role of supernovae in clocking the universe
UChicago News, January 4, 2017
Supernova G299 New research confirms the role Type Ia supernovae, like G299 pictured above, play in measuring universe expansion. <i>Courtesy of NASA</i>
Supernova G299
New research confirms the role Type Ia supernovae, like G299 pictured above, play in measuring universe expansion.
Courtesy of NASA
by Greg Borzo, UChicago News

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)
 
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
 
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
 
Abigail Vieregg has been awarded a Sloan Research Fellowship
The University of Chicago News Office, February 21, 2017
Abigail Vieregg has been awarded a Sloan Research Fellowship
The University of Chicago News Office

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
 
Kumiko Kotera: doing beautiful physics without giving up on family, art and the rest of the world
e-EPS, February 24, 2017
Angela V. Olinto, Homer J. Livingston Professor and Chair Department of Astronomy & Astrophysics
Angela V. Olinto,
Homer J. Livingston Professor and Chair Department of Astronomy & Astrophysics
by Lucia Di Ciaccio, e-EPS

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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Related Links:
KICP Members: Angela V. Olinto
 
New World-Leading Limit on Dark Matter Search from PICO Experiment
SNOLAB News, February 27, 2017
New World-Leading Limit on Dark Matter Search from PICO Experiment
SNOLAB News

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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Related Links:
KICP Members: Juan I. Collar
Scientific projects: COUPP/PICO
 
A recharged debate over the speed of the expansion of the universe could lead to new physics
AAAS, March 8, 2017
A recharged debate over the speed of the expansion of the universe could lead to new physics
by Joshua Sokol, AAAS

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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Related Links:
KICP Members: Wendy L. Freedman; Daniel Scolnic
 
NASA to launch telescope on super-pressure balloon in search for cosmic rays
UChicago News, April 6, 2017
Angela V. Olinto, the Homer J. Livingston Distinguished Service Professor at the University of Chicago and principal investigator the
Angela V. Olinto, the Homer J. Livingston Distinguished Service Professor at the University of Chicago and principal investigator the "Extreme Universe Space Observatory-Super Pressure Balloon" project.
by Greg Borzo, UChicago News

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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Related Links:
KICP Members: Stephan S. Meyer; Angela V. Olinto
KICP Students: Leo Allen; Mikhail Rezazadeh
 
Researchers Provide New Insight Into Dark Matter Halos
University of Pennsylvania, April 19, 2017
An image of a simulated galaxy cluster showing evidence for a boundary, or
An image of a simulated galaxy cluster showing evidence for a boundary, or "edge" from a 2015 paper in the Astrophysical Journal ("The Splashback Radius as a Physical Halo Boundary and the Growth of Halo Mass", The Astrophysical Journal, Volume 810, Issue 1, article id. 36, 16 pp., 2015) by Surhud More, Benedikt Diemer and Andrey Kravtsov.
University of Pennsylvania

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)
 
Virtual Earth-sized telescope aims to capture first image of a black hole
UChicago News, April 21, 2017
Illustration of the environment around the supermassive black hole Sagittarius A*, located some 26,000 light years away at the center the Milky Way.  <i>Illustration by NASA/CXC/M.Weiss</i>
Illustration of the environment around the supermassive black hole Sagittarius A*, located some 26,000 light years away at the center the Milky Way.

Illustration by NASA/CXC/M.Weiss
by Greg Borzo, UChicago News

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)
 
Prof. Angela Olinto hopes telescope will help unravel mysteries of cosmic rays
UChicago News, April 25, 2017
NASA's super-pressure balloon took flight at 10:50 a.m. local time April 25 (5:50 p.m. CST April 24) from Wanaka Airport in New Zealand. Scientists hope the balloon will stay afloat for up to 100 days, more than doubling the previous flight record of 46 days.
NASA's super-pressure balloon took flight at 10:50 a.m. local time April 25 (5:50 p.m. CST April 24) from Wanaka Airport in New Zealand. Scientists hope the balloon will stay afloat for up to 100 days, more than doubling the previous flight record of 46 days.
by Greg Borzo, UChicago News

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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Related Links:
KICP Members: Stephan S. Meyer; Angela V. Olinto
KICP Students: Leo Allen; Mikhail Rezazadeh
 
A Cosmic-Ray Hunter Takes to the Sky
Quanta Magazine, April 28, 2017
Angela Olinto in Wanaka, New Zealand, in March. <i>Alpine Images for Quanta Magazine</i>
Angela Olinto in Wanaka, New Zealand, in March.
Alpine Images for Quanta Magazine
by Natalie Wolchover, Quanta Magazine

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)
 
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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Michael Turner has been elected to American Philosophical Society
UChicago News, May 4, 2017
Michael Turner has been elected to American Philosophical Society
by Ryan Goodwin, UChicago News

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
 
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.

  • Shared Values and Social Goals in Cultural Disciplines
    Yo-Yo Ma, Condeleeza Rice, and other luminaries, including Nobel-winning neurobiologist Eric Kandel, astrophysicist Angela Olinto and entrepreneur Paul Stebbins, to discuss "Shared Values and Social Goals in Cultural Disciplines" - a panel that emphasized, over and over, the importance of risk-taking.
  • Finding the Art's Allies
    This panel, entitled "Finding the Art's Allies: Shared Values and Social Goals in Cultural Disciplines", is moderated by Damian Woetzel. Panelists include Condoleezza Rice, Yo-Yo Ma, Paul Stebbins, Angela Olinto, and Eric R. Kandel, followed by a performance by Hadi Eldebek, Sergio Assad, and Yo-Yo Ma. Afterwards, panelists Oliver Oullier, Jessica Goldman, and Afa Dworkin join the conversation.



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KICP Members: Angela V. Olinto
 
World's most sensitive dark matter detector releases first results
UChicago News, May 18, 2017
XENON1T installation in the underground hall of Laboratori Nazionali del Gran Sasso. The three story building on the right houses various auxiliary systems. The cryostat containing the LXeTPC is located inside the large water tank on the left. <i>Photo by Roberto Corrieri and Patrick De Perio</i>
XENON1T installation in the underground hall of Laboratori Nazionali del Gran Sasso. The three story building on the right houses various auxiliary systems. The cryostat containing the LXeTPC is located inside the large water tank on the left.
Photo by Roberto Corrieri and Patrick De Perio
UChicago News

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
 
Chicago Ideas Week: "Space Exploration: What's After The Final Frontier?"
chicagoideas.com, May 23, 2017
Chicago Ideas Week:
chicagoideas.com

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.
Angela Olinto
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.
Rocky Kolb
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.

Related Links:
KICP Members: Edward W. Kolb; Angela V. Olinto
Scientific projects: Pierre Auger Observatory (AUGER)
 
LIGO detects colliding black holes for third time
UChicago News, June 1, 2017
Reconstructions of the three confident and one candidate gravitational wave signals that LIGO has detected to date, including the most recent detection (GW170104). Believed to truly be millions of years long, only the portion of each signal that LIGO was sensitive to is shown here -- the final seconds leading up to the black hole merger.  <i>Courtesy of LSC/University of Chicago/Ben Farr</i>
Reconstructions of the three confident and one candidate gravitational wave signals that LIGO has detected to date, including the most recent detection (GW170104). Believed to truly be millions of years long, only the portion of each signal that LIGO was sensitive to is shown here -- the final seconds leading up to the black hole merger.

Courtesy of LSC/University of Chicago/Ben Farr
UChicago News

UChicago scientists: Results help unveil diversity of black holes in the universe

The Laser Interferometer Gravitational-Wave Observatory has made a third detection of gravitational waves, providing the latest confirmation that a new window in astronomy has opened. As was the case with the first two detections, the waves -- ripples in spacetime -- were generated when two black holes collided to form a larger black hole.

The latest findings by the LIGO observatory, described in a new paper accepted for publication in Physical Review Letters, builds upon the landmark discovery in 2015 of gravitational waves, which Albert Einstein predicted a century earlier in his theory of general relativity.

"The UChicago LIGO group has played an important role in this latest discovery, including helping to discern what emitted the gravitational waves, testing whether Einstein's theory of general relativity was correct, and exploring whether electromagnetic radiation -- such as visible light, radio, or X-rays -- were also emanated by the black hole collision," said Daniel Holz, associate professor in Physics and Astronomy & Astrophysics, and head of UChicago's LIGO group.

The new detection occurred during LIGO's current observing run, which began Nov. 30, 2016, and will continue through the summer. The newfound black hole formed by the merger has a mass about 49 times that of our sun. The discovery fills in a gap between the systems previously detected by LIGO, with masses of 62 and 21 times that of our sun for the first and second detections, respectively.

"We continue to learn more about this population of heavy stellar-mass black holes, with masses over 20 solar masses, that LIGO has discovered," said LIGO collaborator Ben Farr, a McCormick Fellow at UChicago's Enrico Fermi Institute. "LIGO is making the most direct and pristine observations of black holes that have ever been made, and we're taking large strides in our understanding of how and where these black holes are formed."

LIGO made the first direct observation of gravitational waves in September 2015 during its first observing run. The second detection was made in December 2015, and the third detection, called GW170104, was made on Jan. 4, 2017.

In all three cases, each of the twin detectors of LIGO observed gravitational waves from the tremendously energetic mergers of black hole pairs. The collisions produce more power than is radiated by all of the stars in all of the galaxies in the entire observable universe. The recent detection is the farthest one yet, with the black holes located about 3 billion light-years away. The black holes in the first and second detections were located 1.3 billion and 1.4 billion light-years away, respectively.

"It is truly remarkable that, 100 years after the formulation of general relativity, we are now directly observing some of the most interesting predictions of this theory," said LIGO collaborator Robert Wald, the Charles H. Swift Distinguished Service Professor in Physics at UChicago. "LIGO has opened an entirely new window on our ability to observe phenomena involving strong gravitational fields, and we can look forward to its providing us with many further observations of great astrophysical and cosmological significance in the coming years."

'Looks like Einstein was right'
The LIGO Scientific Collaboration is an international collaboration whose observations are carried out by twin detectors -- one in Hanford, Wash., and the other in Livingston, La. -- operated by California Institute of Technology and Massachusetts Institute of Technology with funding from the National Science Foundation.

The discoveries from LIGO are once again putting Albert Einstein's theories to the test. For example, the researchers looked for an effect called dispersion, in which light waves in a physical medium travel at different speeds depending on their wavelength -- the same way a prism creates a rainbow.

Einstein's general theory of relativity forbids dispersion from happening in gravitational waves as they propagate from their source to Earth, and LIGO's latest detection is consistent with this prediction.

"It looks like Einstein was right -- even for this new event, which is about two times farther away than our first detection," said Laura Cadonati, associate professor of physics at Georgia Institute of Technology and deputy spokesperson for the LIGO Scientific Collaboration. "We can see no deviation from the predictions of general relativity, and this greater distance helps us to make that statement with more confidence."

The LIGO team working with the Virgo Collaboration is continuing to search the latest LIGO data for signs of space-time ripples from the far reaches of the cosmos. They also are working on technical upgrades for LIGO's next run, scheduled to begin in late 2018, during which the detectors' sensitivity will be improved.

"With the detection of GW170104, we are taking another important step toward gravitational-wave astronomy," Holz said. "We now have three solid detections, and these provide our first hints about the diversity of black hole systems in the universe."

LIGO is funded by the National Science Foundation. More than 1,000 scientists from around the world participate in the effort through the LIGO Scientific Collaboration and Virgo Collaboration.

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KICP Members: Ben Farr; Daniel E. Holz; Robert M. Wald
 
Third Gravitational Wave Detection, From Black-Hole Merger 3 Billion Light Years Away
The New York Times, June 8, 2017
by Dennis Overbye, The New York Times

This is the third black-hole smashup that astronomers have detected since they started keeping watch on the cosmos back in September 2015, with LIGO, the Laser Interferometer Gravitational-Wave Observatory. All of them are more massive than the black holes that astronomers had previously identified as the remnants of dead stars.

...

As for the original stellar identities of these dark dancers, the consensus, said Daniel Holz of the University of Chicago, is that they were probably very massive and primitive stars at least 40 times heavier than the sun.

According to theoretical calculations, stars composed of primordial hydrogen and helium and lacking heavier elements like oxygen and carbon, which astronomers with their knack for nomenclature call "metals," can grow monstrously large. They could collapse directly into black holes when their brief violent lives were over without the benefit of a supernova explosion or other cosmic fireworks.

Dr. Holz said in an email: "It is indeed odd to think that some of the most dramatic stellar collapse do not result in massive stellar explosions outshining galaxies, but instead just involve a star winking out of existence. But that's what the theory says should happen."

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KICP Members: Daniel E. Holz
 
Hubble pushed beyond limits to spot clumps of new stars in distant galaxy
UChicago News, July 10, 2017
The magnified image at right shows how the galaxy would look to Hubble without distortions -- the disk galaxy containing clumps of star formation that each span about 200 to 300 light-years. <i>Image credit</i>: NASA, ESA, and T. Johnson (University of Michigan)
The magnified image at right shows how the galaxy would look to Hubble without distortions -- the disk galaxy containing clumps of star formation that each span about 200 to 300 light-years.
Image credit: NASA, ESA, and T. Johnson (University of Michigan)
UChicago News

When it comes to the distant universe, even the keen vision of NASA's Hubble Space Telescope can only go so far. Teasing out finer details requires clever thinking and a little help from a cosmic alignment with a gravitational lens.

By applying a new computational analysis to a galaxy magnified by a gravitational lens, astronomers have obtained images ten times sharper than what Hubble could achieve on its own. The results show an edge-on disk galaxy studded with brilliant patches of newly formed stars.

"When we saw the reconstructed image we said, 'Wow, it looks like fireworks are going off everywhere,'" said astronomer Jane Rigby of NASA's Goddard Space Flight Center in Greenbelt, Md.

The galaxy in question is so far away that we see it as it appeared 11 billion years ago, only 2.7 billion years after the big bang. It is one of more than 70 strongly lensed galaxies studied by the Hubble Space Telescope, following up targets selected by the Sloan Giant Arcs Survey, which discovered hundreds of strongly lensed galaxies by searching Sloan Digital Sky Survey imaging data covering one-fourth of the sky.

"Mining the Sloan Digital Sky Survey has given us the opportunity to peer inside a distant star-forming galaxy with a sharpness of vision never before allowed," said Michael Gladders, associate professor in Astronomy and Astrophysics at the University of Chicago. "Admittedly, it's a highly distorted view -- like looking at your reflection in the famous Chicago 'Bean' -- but with some work we can and have reconstructed a detailed image of the distant galaxy."
Galaxy cluster
The galaxy cluster shown here was discovered as part of the Sloan Giant Arcs Survey. It is located about 6 billion light-years from Earth and contains hundreds of galaxies

Researchers had been grappling with the gravity of a giant cluster of galaxies between the target galaxy and Earth that distorts the more distant galaxy's light, stretching it into an arc and also magnifying it almost 30 times. The team had to develop special computer code to remove the distortions caused by the gravitational lens, and reveal the distant galaxy as it would normally appear.

The resulting reconstructed image revealed two dozen clumps of newborn stars, each spanning about 200 to 300 light-years. This contradicted theories suggesting that star-forming regions in the distant, early universe were much larger: 3,000 light-years or more in size.

"There are star-forming knots as far down in size as we can see," said doctoral student Traci Johnson of the University of Michigan, lead author of two of the three papers describing the research.

Without the magnification boost of the gravitational lens, Johnson added, the disk galaxy would appear perfectly smooth and unremarkable to Hubble. This would give astronomers a very different picture of where stars are forming.

While Hubble highlighted new stars within the lensed galaxy, NASA's James Webb Space Telescope will uncover older, redder stars that formed even earlier in the galaxy's history. It will also peer through any obscuring dust within the galaxy.

"With the Webb Telescope, we'll be able to tell you what happened in this galaxy in the past, and what we missed with Hubble because of dust," said Rigby.

These findings appear in a paper published in The Astrophysical Journal Letters and two additional papers published in The Astrophysical Journal.

The Hubble Space Telescope, which is named after UChicago alumnus Edwin Hubble, is a project of international cooperation between NASA and the European Space Agency. NASA's Goddard Space Flight Center manages the telescope. The Space Telescope Science Institute in Baltimore, Md., conducts Hubble science operations. The institute is operated for NASA by the Association of Universities for Research in Astronomy in Washington, D.C.

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KICP Members: Michael D. Gladders
Scientific projects: Sloan Digital Sky Survey (SDSS)
 
Angela Olinto has been named the Albert A. Michelson Distinguished Service Professor
UChicago News, July 12, 2017
Angela V. Olinto, KICP senior member
Angela V. Olinto, KICP senior member
UChicago News

Angela V. Olinto has been named the Albert A. Michelson Distinguished Service Professor in Astronomy and Astrophysics and the College.

Olinto works on astroparticle physics and cosmology. She has made important contributions to the physics of quark stars, inflationary theory, cosmic magnetic fields and astroparticle physics. She currently leads NASA sub-orbital and space missions to discover the origins of the highest-energy cosmic rays and neutrinos.

Olinto is an elected fellow of the American Association for the Advancement of Science and the American Physical Society, and has received the Chaire d'Excellence Award of the French Agence Nationale de Recherche, the Quantrell Award for Excellence in Undergraduate Teaching, and the Faculty Award for Excellence in Graduate Teaching and Mentoring, among other awards. She serves as chair of the Department of Astronomy and Astrophysics at the University.

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KICP Members: Angela V. Olinto
 
KICP graduate students Carlos Blanco and Maya Fishbach awarded the NSF Graduate Research Fellowship
UChicago News, July 17, 2017
KICP graduate students Carlos Blanco and Maya Fishbach awarded the NSF Graduate Research Fellowship
UChicago News

Carlos Blanco, a PhD candidate in astro-particle physics, studies possible particle dark matter models and looks at gamma rays to determine if they are coming from dark matter. "Right now, our understanding of the universe is extremely small," explains Blanco. "Twenty-seven percent of the energy content of the universe is dark matter, and we don't understand the nature of dark matter at all." Blanco is also working on a Raspberry Pi-based educational platform that aims to teach children in Colombia the principles of coding and engineering and how to build water quality sensors.

Maya Fishbach, a PhD candidate in astronomy and astrophysics, studies where and how black holes form. As a member of LIGO, the Laser Interferometer Gravitational-Wave Observatory, Fishbach utilizes detections of merging black hole binaries, which emit fairly "loud" gravitational waves in the last few seconds of their evolution. "Black holes are not intuitively understood, which makes them very exciting to study," says Fishbach. "When black holes collide, they emit a lot of energy in the form of gravitational waves, and these waves carry information about their properties." Fishbach recently published a paper in Astrophysical Journal Letters.

The award offers recognition and financial support for outstanding graduate students in science, technology and engineering fields supported by the NSF.

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Related Links:
KICP Members: Daniel E. Holz; Daniel Hooper
KICP Students: Carlos Blanco; Maya Fishbach
 
Tiny scientists mobilized to study solar eclipse
Chicago Suntimes, July 26, 2017
Jason Henning (left), a post-doctoral fellow at the Kavli Institute for Cosmological Physics at the University of Chicago, talks about eclipses with children Tuesday at the Bright Horizons at Lakeview, a Chicago pre-school on Lincoln Avenue. <i>Credit:</i> Neil Steinberg/Sun-Times
Jason Henning (left), a post-doctoral fellow at the Kavli Institute for Cosmological Physics at the University of Chicago, talks about eclipses with children Tuesday at the Bright Horizons at Lakeview, a Chicago pre-school on Lincoln Avenue. Credit: Neil Steinberg/Sun-Times
by Neil Steinberg, Chicago Suntimes

Jason Henning is a post-doctorate fellow at the Kavli Institute for Cosmological Physics at the University of Chicago. He's been to the South Pole three times, working on the university's 10-meter telescope there.

On Tuesday morning, he found himself advancing science in a place it doesn't frequently go: sitting on a too small chair in a basement classroom with the lights dimmed.

"Who's ready for an eclipse?" he asked a group of 4- and 5-year-olds sitting around a table at Bright Horizons at Lakeview, a preschool.

The youngsters didn't exactly squeal "Yes!" in unison, but they at least cast their attention in his general direction. Henning proceeded, using a small model Earth, moon and, as a light source, a lamp with a dinosaur base.

"Does anybody know how you make night and day?" asked Henning. "Does anybody remember?"

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KICP Members: Jason Henning
KICP Students: Joshua Sobrin
Scientific projects: South Pole Telescope (SPT)
 
Dark Energy Survey reveals most precise measure of universe's structure
UChicago News, August 3, 2017
A map of dark matter covering about one -- thirtieth of the entire sky and spanning several billion light years -- red regions have more dark matter than average, blue regions less dark matter.  <i>Courtesy of Chihway Chang, the DES collaboration</i>
A map of dark matter covering about one -- thirtieth of the entire sky and spanning several billion light years -- red regions have more dark matter than average, blue regions less dark matter.
Courtesy of Chihway Chang, the DES collaboration
UChicago News

Result supports view that dark matter, dark energy make up most of cosmos

Imagine planting a single seed and, with great precision, being able to predict the exact height of the tree that grows from it. Now imagine traveling to the future and snapping photographic proof that you were right.

If you think of the seed as the early universe, and the tree as the universe the way it looks now, you have an idea of what the international Dark Energy Survey collaboration has just done. Scientists unveiled their most accurate measurement of the present large-scale structure of the universe at a meeting Aug. 3 at the University of Chicago-affiliated Fermi National Accelerator Laboratory. UChicago, Argonne and Fermilab scientists are members of international Dark Energy Survey collaboration.

These measurements of the amount and "clumpiness" (or distribution) of dark matter in the present-day cosmos were made with a precision that, for the first time, rivals that of inferences from the early universe by the European Space Agency's orbiting Planck observatory. The new Dark Energy Survey result (the tree, in the above metaphor) is close to "forecasts" made from the Planck measurements of the distant past (the seed), allowing scientists to understand more about the ways the universe has evolved over 14 billion years.

"This result is beyond exciting," said Fermilab's Scott Dodelson, a professor in the Department of Astronomy and Astrophysics at UChicago and one of the lead scientists on this result, which was announced at the American Physical Society Division of Particles and Fields meeting. "For the first time, we're able to see the current structure of the universe with the same clarity that we can see its infancy, and we can follow the threads from one to the other, confirming many predictions along the way."

Most notably, this result supports the theory that 26 percent of the universe is in the form of mysterious dark matter and that space is filled with an also-unseen dark energy, which makes up 70 percent and is causing the accelerating expansion of the universe.

Paradoxically, it is easier to measure the large-scale clumpiness of the universe in the distant past than it is to measure it today. In the first 400,000 years following the Big Bang, the universe was filled with a glowing gas, the light from which survives to this day. The Planck observatory's map of this cosmic microwave background radiation gives us a snapshot of the universe at that very early time. Since then, the gravity of dark matter has pulled mass together and made the universe clumpier over time. But dark energy has been fighting back, pushing matter apart. Using the Planck map as a start, cosmologists can calculate precisely how this battle plays out over 14 billion years.

"These first major cosmology results are a tribute to the many people who have worked on the project since it began 14 years ago," said Dark Energy Survey Director Josh Frieman, a scientist at Fermilab and a professor in the Department of Astronomy and Astrophysics at UChicago. "It was an exciting moment when we unveiled the results to ourselves just last month, after carrying out a 'blind' analysis to avoid being influenced by our prejudices."

The Dark Energy Survey is a collaboration of more than 400 scientists from 26 institutions in seven countries. Its primary instrument is the 570-megapixel Dark Energy Camera, one of the most powerful in existence, which is able to capture digital images of light from galaxies eight billion light years from Earth. The camera was built and tested at Fermilab, the lead laboratory on the Dark Energy Survey, and is mounted on the National Science Foundation's four-meter Blanco telescope, part of the Cerro Tololo Inter-American Observatory in Chile. The DES data are processed at the National Center for Supercomputing Applications at the University of Illinois at Urbana-Champaign.

Scientists are using the camera to map an eighth of the sky in unprecedented detail over five years. The fifth year of observation will begin this month. The new results draw only from data collected during the survey's first year, which covers one-thirtieth of the sky.

Scientists used two methods to measure dark matter. First, they created maps of galaxy positions as tracers, and second, they precisely measured the shapes of 26 million galaxies to directly map the patterns of dark matter over billions of light years, using a technique called gravitational lensing.

To make these ultra-precise measurements, the team developed new ways to detect the tiny lensing distortions of galaxy images - an effect not even visible to the eye, enabling revolutionary advances in understanding these cosmic signals. In the process, they created the largest guide to spotting dark matter in the cosmos ever drawn. The new dark matter map is ten times the size of the one that the Dark Energy Survey released in 2015 and will eventually be three times larger than it is now.

"The Dark Energy Survey has already delivered some remarkable discoveries and measurements, and they have barely scratched the surface of their data," said Fermilab Director Nigel Lockyer. "Today's world-leading results point forward to the great strides DES will make toward understanding dark energy in the coming years."

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Related Links:
KICP Members: Chihway Chang; Scott Dodelson; Joshua A. Frieman
Scientific projects: Dark Energy Survey (DES)
 
Dark Energy Survey reveals most accurate measurement of dark matter structure in the universe
Fermilab News, August 3, 2017
Composite picture of stars over the Cerro Tololo Inter-American Observatory in Chile.  <i>Photo: Reidar Hahn/Fermilab</i>
Composite picture of stars over the Cerro Tololo Inter-American Observatory in Chile.
Photo: Reidar Hahn/Fermilab
Fermilab News

Imagine planting a single seed and, with great precision, being able to predict the exact height of the tree that grows from it. Now imagine traveling to the future and snapping photographic proof that you were right.

If you think of the seed as the early universe, and the tree as the universe the way it looks now, you have an idea of what the Dark Energy Survey (DES) collaboration has just done. In a presentation today at the American Physical Society Division of Particles and Fields meeting at the U.S. Department of Energy's (DOE) Fermi National Accelerator Laboratory, DES scientists will unveil the most accurate measurement ever made of the present large-scale structure of the universe.

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Related Links:
KICP Members: Scott Dodelson; Joshua A. Frieman
Scientific projects: Dark Energy Survey (DES)
 
World's smallest neutrino detector observes elusive interactions of particles
UChicago News, August 4, 2017
Prof. Juan Collar led a team of UChicago physicists who built a lightweight, portable neutrino detector to observe the elusive interactions of the ghostly particles.
Prof. Juan Collar led a team of UChicago physicists who built a lightweight, portable neutrino detector to observe the elusive interactions of the ghostly particles.
by Steve Koppes, UChicago News

UChicago physicists play leading role in confirming theory predicted four decades ago

In 1974, a Fermilab physicist predicted a new way for ghostly particles called neutrinos to interact with matter. More than four decades later, a UChicago-led team of physicists built the world's smallest neutrino detector to observe the elusive interaction for the first time.

Neutrinos are a challenge to study because their interactions with matter are so rare. Particularly elusive has been what's known as coherent elastic neutrino-nucleus scattering, which occurs when a neutrino bumps off the nucleus of an atom.

The international COHERENT Collaboration, which includes physicists at UChicago, detected the scattering process by using a detector that's small and lightweight enough for a researcher to carry. Their findings, which confirm the theory of Fermilab's Daniel Freedman, were reported Aug. 3 in the journal Science.

"Why did it take 43 years to observe this interaction?" asked co-author Juan Collar, UChicago professor in physics. "What takes place is very subtle." Freedman did not see much of a chance for experimental confirmation, writing at the time: "Our suggestion may be an act of hubris, because the inevitable constraints of interaction rate, resolution and background pose grave experimental difficulties."

When a neutrino bumps into the nucleus of an atom, it creates a tiny, barely measurable recoil. Making a detector out of heavy elements such as iodine, cesium or xenon dramatically increases the probability for this new mode of neutrino interaction, compared to other processes. But there's a trade-off, since the tiny nuclear recoils that result become more difficult to detect as the nucleus grows heavier.

"Imagine your neutrinos are ping-pong balls striking a bowling ball. They are going to impart only a tiny extra momentum to this bowling ball," Collar said.

To detect that bit of tiny recoil, Collar and colleagues figured out that a cesium iodide crystal doped with sodium was the perfect material. The discovery led the scientists to jettison the heavy, gigantic detectors common in neutrino research for one similar in size to a toaster.

No gigantic lab
The 4-inch-by-13-inch detector used to produce the Science results weighs only 32 pounds (14.5 kilograms). In comparison, the world's most famous neutrino observatories are equipped with thousands of tons of detector material.

"You don't have to build a gigantic laboratory around it," said UChicago doctoral student Bjorn Scholz, whose thesis will contain the result reported in the Science paper. "We can now think about building other small detectors that can then be used, for example to monitor the neutrino flux in nuclear power plants. You just put a nice little detector on the outside, and you can measure it in situ."

Neutrino physicists, meanwhile, are interested in using the technology to better understand the properties of the mysterious particle.

"Neutrinos are one of the most mysterious particles," Collar said. "We ignore many things about them. We know they have mass, but we don't know exactly how much."

Through measuring coherent elastic neutrino-nucleus scattering, physicists hope to answer such questions. The COHERENT Collaboration's Science paper, for example, imposes limits on new types of neutrino-quark interactions that have been proposed.

The results also have implications in the search for Weakly Interacting Massive Particles. WIMPs are candidate particles for dark matter, which is invisible material of unknown composition that accounts for 85 percent of the mass of the universe.

"What we have observed with neutrinos is the same process expected to be at play in all the WIMP detectors we have been building," Collar said.

Neutrino alley
The COHERENT Collaboration, which involves 90 scientists at 18 institutions, has been conducting its search for coherent neutrino scattering at the Spallation Neutron Source at Oak Ridge National Laboratory in Tennessee. The researchers installed their detectors in a basement corridor that became known as "neutrino alley." This corridor is heavily shielded by iron and concrete from the highly radioactive neutron beam target area, only 20 meters (less than 25 yards) away.

This neutrino alley solved a major problem for neutrino detection: It screens out almost all neutrons generated by the Spallation Neutron Source, but neutrinos can still reach the detectors. This allows researchers to more clearly see neutrino interactions in their data. Elsewhere they would be easily drowned out by the more prominent neutron detections.

The Spallation Neutron Source generates the most intense pulsed neutron beams in the world for scientific research and industrial development. In the process of generating neutrons, the SNS also produces neutrinos, though in smaller quantities.

"You could use a more sophisticated type of neutrino detector, but not the right kind of neutrino source, and you wouldn't see this process," Collar said. "It was the marriage of ideal source and ideal detector that made the experiment work."

Two of Collar's former graduate students are co-authors of the Science paper: Phillip Barbeau, AB'01, SB'01, PhD'09, now an assistant professor of physics at Duke University; and Nicole Fields, PhD'15, now a health physicist with the U.S. Nuclear Regulatory Commission in Chicago.

The development of a compact neutrino detector brings to fruition an idea that UChicago alumnus Leo Stodolsky, SM'58, PhD'64, proposed in 1984. Stodolsky and Andrzej Drukier, both of the Max Planck Institute for Physics and Astrophysics in Germany, noted that a coherent detector would be relatively small and compact, unlike the more common neutrino detectors containing thousands of gallons of water or liquid scintillator. In their work, they predicted the arrival of future neutrino technologies made possible by the miniaturization of the detectors.

Scholz, the UChicago graduate student, saluted the scientists who have worked for decades to create the technology that culminated in the detection of coherent neutrino scattering.

"I cannot fathom how they must feel now that it's finally been detected, and they've achieved one of their life goals," Scholz said. "I've come in at the end of the race. We definitely have to give credit to all the tremendous work that people have done before us."

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Related Links:
KICP Members: Juan I. Collar
KICP Students: Bjorn Scholz
Scientific projects: Coherent Germanium Neutrino Technology (CoGeNT)
 
Ever-Elusive Neutrinos Spotted Bouncing Off Nuclei for the First Time
Scientific American, August 4, 2017
SNS's Beamline 13, which carries neutrons from the SNS collider to experimental stations. The same process that produces the neutrons also spits out neutrinos, which enter the COHERENT detector in the SNS basement.  <i>Credit: Jean Lachat University of Chicago.</i>
SNS's Beamline 13, which carries neutrons from the SNS collider to experimental stations. The same process that produces the neutrons also spits out neutrinos, which enter the COHERENT detector in the SNS basement.
Credit: Jean Lachat University of Chicago.
by Jesse Dunietz, Scientific American

A new technology for detecting neutrinos represents a "monumental" advance for science.

Juan Collar, a professor in physics at the University of Chicago, with a prototype of the world's smallest neutrino detector used to observe for the first time an elusive interaction known as coherent elastic neutrino nucleus scattering.

Neutrinos are famously antisocial. Of all the characters in the particle physics cast, they are the most reluctant to interact with other particles. Among the hundred trillion neutrinos that pass through you every second, only about one per week actually grazes a particle in your body.

That rarity has made life miserable for physicists, who resort to building huge underground detector tanks for a chance at catching the odd neutrino. But in a study published today in Science, researchers working at Oak Ridge National Laboratory (ORNL) detected never-before-seen neutrino interactions using a detector the size of a fire extinguisher. Their feat paves the way for new supernova research, dark matter searches and even nuclear nonproliferation monitoring.

Under previous approaches, a neutrino reveals itself by stumbling across a proton or neutron amidst the vast emptiness surrounding atomic nuclei, producing a flash of light or a single-atom chemical change. But neutrinos deign to communicate with other particles only via the "weak" force -- the fundamental force that causes radioactive materials to decay. Because the weak force operates only at subatomic distances, the odds of a tiny neutrino bouncing off of an individual neutron or proton are miniscule. Physicists must compensate by offering thousands of tons of atoms for passing neutrinos to strike.

The new experimental collaboration, known as COHERENT, instead looks for a phenomenon called CEvNS (pronounced "sevens"), or coherent elastic neutrino-nucleus scattering. CEvNS relies on the quantum mechanical equivalence between particles and waves, comparable to ocean waves. The high-energy neutrinos sought by most experiments are like short, choppy ocean waves. When such narrow waves pass under floating debris, they can pick out one leaf or twig at a time to toss around. Similarly, a high-energy neutrino typically picks out individual protons and neutrons with which to interact. But just as a long, slow wave would pick up the whole patch of debris at once, a low-energy neutrino sees the entire atomic nucleus as one "coherent" whole. This dramatically improves the odds of an interaction. As the number of neutrons in the nucleus is increased, the effective target size for the neutrino to hit grows in lockstep not just with that number, but with its square.

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Related Links:
KICP Members: Juan I. Collar
Scientific projects: Coherent Germanium Neutrino Technology (CoGeNT)
 
New sky survey shows that dark energy may one day tear us apart
New Scientist, August 7, 2017
Measurements reveal a mismatch. <i>Image credit: Reidar Hahn, Fermilab</i>
Measurements reveal a mismatch.
Image credit: Reidar Hahn, Fermilab
by Shannon Hall, New Scientist

The fate of the universe just became a little less certain. That's due to a disagreement between a map of the early universe and a new map of today's universe. If the mismatch stands the test of future measurements, we might have to rewrite physics. But that is a pretty big if.

The new results, which are part of the ongoing Dark Energy Survey (DES), charted the distribution of matter across 26 million galaxies in a large swathe of the southern sky.

"This is one of the most powerful pictures of the universe today that we've ever had," says Daniel Scolnic at the University of Chicago, who is a part of the 400-person DES collaboration but wasn't involved in this work.

It is so powerful because knowing the distribution, or clumpiness, of galaxies helps us better understand the cosmic game of tug of war as dark energy - a mysterious force that causes the universe to accelerate - pulls each galaxy apart, and dark matter - a theoretical but still unseen form of matter - pushes each galaxy together.

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KICP Members: Daniel Scolnic
Scientific projects: Dark Energy Survey (DES)
 
Eclipse reflects sun's historic power
UChicago News, August 16, 2017
Michael Turner, KICP director
Michael Turner, KICP director
UChicago News

Eclipses have fascinated people since the earliest days of recorded history.

These rare astronomical events have helped explain the world around us -- from ancient Mesopotamia, where they were believed to foretell the deaths of kings, all the way to the 20th century, when they helped prove Einstein's theory of general relativity.

Such interest hasn't dimmed. People across the United States will have an opportunity on Aug. 21 to witness the first total solar eclipse from coast to coast in 99 years. UChicago faculty and students are among the hordes of enthusiasts traveling across the country toward the area of "totality," the 70-mile-wide stripe stretching from Oregon to South Carolina in which the moon will fully block the sun.

Ahead of this historic event, UChicago News asked scholars in fields ranging from theoretical cosmology to Islamic studies to discuss eclipses and their power.


The eclipse that proved Einstein was right
Michael Turner, Bruce V. & Diana M. Rauner Distinguished Service Professor in Physics

"Astronomers have learned a lot from eclipses, including one in 1919 that proved Einstein was right.

At the time, only a handful of people were aware of general relativity; Sir Arthur Eddington was one of them. He led an eclipse expedition into the Atlantic to find out whether gravity would bend starlight, as predicted by general relativity. What you want to do is look at stars very close to the sun, and see whether the light coming toward us is bent by the sun's gravity. With the moon blocking the sun, you can get that measurement, and it was exactly what Einstein predicted. The scientific community was agog. It instantly put general relativity on the map, and made Einstein a rockstar.

We're still learning things from eclipses. One thing people will study during this event is the corona of the sun, which is the glowing aura of gases that surrounds the sun. There are still things we don't understand about it -- such as exactly why it actually burns hundreds of times hotter than the surface of the sun itself.

A few years from now, NASA will launch a probe named after UChicago's own Eugene Parker that will explore the sun's corona -- closer than any probe has ever come to the sun."


The royal omen
John Wee, Assistant Professor of Assyriology

"Neo-Assyrian politics were swayed by the movements of sun, moon and planets. The courts of Kings Esarhaddon (681 - 669 B.C.) and Assurbanipal (668 - c. 627 B.C.), in particular, were full of scholars who competed for the king's favor by issuing advice based on astronomical predictions.

To ancient Mesopotamians, eclipses portended misfortune, and their dramatic manifestations constituted omens of enough significance to affect the entire land or the king himself. Even a partial eclipse could be as interesting -- if not more so -- than a full eclipse. Depending on the quadrant of the sun or moon obscured, misfortune was directed toward lands in the north, south, east or west. Because the moon was sometimes compared to a 'crown,' lunar eclipses especially foretold the deaths of kings.

"An eclipse was almost always a royal omen; in particular, a lunar eclipse foretold the death of a king."

But there were ways of averting the misfortune. Certain prayers and incantations implored the gods to mitigate the omen. A so-called substitute king ritual furnished an escape for the king whose death had been foretold by eclipse: The real king leaves the court and is addressed as 'the farmer,' while a prisoner is dressed up and put on the throne for a short time before he's executed -- thereby fulfilling the prophecy.

So, bad for the prisoner, but eclipses are very useful for us historians. A famous solar eclipse, dated by modern methods to 15 June 763 B.C., provides a fixed point on which to anchor the chronology of Mesopotamian history in the first millennium B.C."


Eclipse dragons
Persis Berlekamp, Associate Professor of Art History

"Astrology informed a great deal of medieval Islamic art. It references the solar calendar, which in any preindustrial society, is extremely important -- it tells you when to plant, when to go to war, when to lay foundations for buildings. Any court had its astrological advisors, who had their own fans and enemies.

One motif you see in both the art and architecture of the 12th and 13th centuries, particularly from Anatolia to Iraq, is called an eclipse dragon. It appears as a stylized knotted dragon, and it's a reconciliation of ancient Near Eastern belief and what the astronomers of the day knew about the science of eclipses.

According to ancient mythology, an eclipse happened when a giant celestial dragon swallowed the sun and the moon. But the medieval astronomers knew it happened when the sun and moon and the earth all lined up. So they reconciled these ideas by creating this invisible, theoretical entity, the 'eclipse dragon,' moving around in the sky. When its head and tail correspond to the 'nodes' where the courses of the heavenly bodies cross when eclipses happen, that's when the dragon swallows the moon and sun.

They're associated with chaos, occlusion, uncertainty. It's an idea that really resonated in the 12th and 13th centuries because that was a very tumultuous period for this area. The Mongols were moving across Central Asia toward Baghdad, and each time they advanced, they pushed waves of refugees further west. It was a violent time with a lot of social upheaval.

So it's exactly at this time that these dragons appeared on all sorts of objects, and also on civic architecture, like bridges and city walls. They were expected to help protect against the sudden onset of darkness that they represent. The most famous example is the 'Talisman Gate' of medieval Baghdad. The prince is holding back the forces of chaos and darkness, shown as eclipse dragons.

It's very different from how we think about mythology and science today. In our world, it is necessary and important that educated people uphold the boundary between them. But this is an example from another era when intelligent, educated people answered to both simultaneously. If we can get our heads around that, it really expands our understanding of the range of ways art has mattered in the long, varied, history of human experience."


Ordinary end-of-days
Alireza Doostdar, Assistant Professor of Islamic Studies and the Anthropology of Religion

"In the Islamic tradition, a solar eclipse is both ordinary and extraordinary. It is extraordinary in the sense that it disrupts our everyday expectation of night and day and their regularity; in this sense, it is another sign of God's power. It is ordinary in the sense that it is part of a divine plan and has no significance beyond its attestation of divine omnipotence.

There is a famous story about a solar eclipse that occurred right after the death of the prophet Muhammad's child Ibrahim. Some in the Muslim community took this to be an omen or a sign that the sun was grieving. But Muhammad insisted that an eclipse was merely a sign of God, and people should take the opportunity to pray. To this day, many Muslims pray the 'salat al-kusuf' (solar eclipse prayer) or 'salat al-ayat' (prayer of signs) when a solar eclipse occurs in their vicinity.

While eclipses are ordinary in the sense I have described, Islamic descriptions of the end times and Judgment Day often include phenomena that resemble a lunar or solar eclipse (or both at the same time). For example, Chapter 75 of the Qur'an reads, in part: 'So when vision is dazzled, and the moon darkens, and the sun and the moon are joined, man will say on that Day, 'Where is the escape?' No! There is no refuge. To your Lord, that Day, is the place of permanence.'

With these end-times accounts in mind, we can see a solar eclipse as yet another kind of sign: A reminder that the end of our world may have something to do with the death of our sun, and that ultimately, even something as seemingly permanent as the sun will one day cease to be."

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KICP Members: Michael S. Turner