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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Related Links:
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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