Department in the News

Researchers advocate statistical approach to search for Earth-like planets
June 13, 2017
Assoc. Prof. Jacob Bean
UChicago News, by Steve Koppes
Proposal touts value of broader, less detailed studies of exoplanets

A team of astronomers at the University of Chicago and Grinnell College seeks to change the way scientists approach the search for Earth-like planets orbiting stars other than the sun. They favor taking a statistical comparative approach in seeking habitable planets and life beyond the solar system.

"The nature of proof should not be: 'Can we point at a planet and say, yes or no, that's the planet hosting alien life," said Jacob Bean, associate professor of astronomy and astrophysics at UChicago. "It's a statisical exercise. What can we say for an ensemble of planets about the frequency of the existence of habitable environments, or the frequency of the existence of life on those planets?"

The standard approach of researching exoplanets, or planets that orbit distant stars, has entailed studying small numbers of objects to determine if they have the right gases in the appropriate quantities and ratios to indicate the existence of life. But in a recent paper with co-authors Dorian Abbot and Eliza Kempton in the Astrophysical Journal Letters, Bean describes the need "to think about the techniques and approaches of astronomy in this game -- not as planetary scientists studying exoplanets."

"Nature has provided us with huge numbers of planetary systems," said Kempton, an assistant professor of physics at Grinnell College in Iowa. "If we survey a large number of planets with less detailed measurements, we can still get a statistical sense for how prevalent habitable environments are in our galaxy. This would give us a basis for future, more detailed surveys."

Kempton and Bean attest to the challenges of making detailed observations of a potentially Earth-like planet. Together they have previously studied the super-Earth known as GJ 1214b, an exoplanet with a mass greater than Earth's but less than gas giants such as Neptune and Uranus. GJ 1214b turned out to be quite cloudy, which prevented them from determining the composition of its atmosphere.

"A large statistical study will allow us to look at many planets," Kempton said. "If any single object proves to be particularly challenging to observe, like GJ 1214b, that won't be a major loss to the observing program on the whole."

Kepler observatory a game-changer
The inspiration for the paper stemmed from Bean's membership on the Science and Technology Definition Team that is assessing the potential for a new space telescope, NASA's proposed Large UV/Optical/Infrared Survey (LUVOIR).

One of LUVOIR's scientific priorities is the search for Earth-like planets. During one team meeting, Bean and his colleagues listed all the properties of a potentially habitable exoplanet that they need to measure and how they would go about obtaining the data. Given the current state of technology, Bean concluded that it's unlikely scientists will be able to confirm an individual exoplanet as suitable for life or whether life is actually there.

Nevertheless, astronomers have gathered an impressive haul of exoplanetary data from NASA's Kepler space observatory, which has operated since 2009.

"Kepler completely changed the game," Bean said. "Instead of talking about a few planets or a few tens of planets, all of a sudden we had a few thousand planet candidates. They were planet candidates because Kepler couldn't definitely prove that the signal it was seeing was due to planets."

The standard approach has been to take additional observations for each candidate to rule out possible false positive scenarios, or to detect the planet with a second technique.

"That's very slow going. One planet at a time, a lot of different observations," Bean noted. But an alternative is to make statistical calculations for the probability of false positives among these thousands of exoplanet candidates. That new approach led directly to a good understanding of the frequency of exoplanets of different sizes. For example, scientists now can say that the frequency of super-Earth-type planets is 15 percent, plus or minus 5 percent.

Role of spectroscopy
Spectroscopic studies play a key role in characterizing exoplanets. This involves determining the composition of a planetary atmosphere by measuring its spectra, the distinctive radiation that gases absorb at their own particular wavelengths. Bean and his co-authors suggest focusing on what can be learned from measuring the spectra of a large ensemble of terrestrial exoplanets.

Spectroscopy may, for example, help exoplanetary researchers verify a phenomenon called the silicate weathering feedback, which acts as a planetary thermostat. Through silicate weathering, the amount of atmospheric carbon dioxide varies according to geologic processes. Volcanoes emit carbon dioxide into the atmosphere, but rain and chemical reactions that occur in rocks and sediments also remove the gas from the atmosphere.

Rising temperatures would put more water vapor into the atmosphere, which then rains out, increasing the amount of dissolved carbon dioxide that chemically interacts with the rocks. This loss of carbon dioxide from the atmosphere has a cooling effect. But as a planet begins to cool, rock weathering slows and the amount of carbon dioxide gradually builds from its volcanic sources, which causes rising temperatures.

Global-scale observations suggest that Earth has experienced silicate-weathering feedback. But attempts to verify that the process is operating today on the scale of individual river basins has proven difficult.

"The results are very noisy. There's no clear signal," Abbot said. "It would be great to have another independent confirmation from exoplanets."

All three co-authors are interested in fleshing out the details of experiments they proposed in their paper. Abbot plans to calculate how much carbon dioxide would be necessary to keep a planet habitable at a range of stellar radiation intensities while changing various planetary parameters. He also will assess how well a future instrument would be able to measure the gas.

"Then we will put this together to see how many planets we would need to observe to detect the trend indicating a silicate-weathering feedback," Abbot explained.

Bean and Kempton, meanwhile, are interested in detailing what a statistical census of biologically significant gases such as oxygen, carbon dioxide and ozone could reveal about planetary habitability.

"I'd like to get a better understanding of how some of the next-generation telescopes will be able to distinguish statistical trends that indicate habitable -- or inhabited -- planets," Kempton said.

Citation: "A statistical comparative planetology approach to the hunt for habitable exoplanets and life beyond the solar system," by Jacob L. Bean, Dorian S. Abbot and Eliza M.-R. Kempton, Astrophysical Journal Letters. Doi: 10.3847/2041-8213/aa738a/.

Funding: David and Lucile Packard Foundation, National Aeronautics and Space Administration, Research Corporation for Science Advancement, and Grinnell College's Harris Faculty Fellowship.

Related:
Department members: Jacob L. Bean

Parker Solar Probe: Humanity's First Visit to a Star
June 5, 2017
NASA
NASA has renamed the Solar Probe Plus spacecraft -- humanity's first mission to a star, which will launch in 2018 -- as the Parker Solar Probe in honor of astrophysicist Eugene Parker. The announcement was made at a ceremony at the University of Chicago, where Parker serves as the S. Chandrasekhar Distinguished Service Professor Emeritus, Department of Astronomy and Astrophysics.

Launch Window: July 31 - Aug. 19, 2018
NASA's historic Parker Solar Probe mission will revolutionize our understanding of the sun, where changing conditions can propagate out into the solar system, affecting Earth and other worlds. Parker Solar Probe will travel through the sun's atmosphere, closer to the surface than any spacecraft before it, facing brutal heat and radiation conditions - and ultimately providing humanity with the closest-ever observations of a star.

Journey to the Sun
In order to unlock the mysteries of the sun's atmosphere, Parker Solar Probe will use Venus' gravity during seven flybys over nearly seven years to gradually bring its orbit closer to the sun. The spacecraft will fly through the sun's atmosphere as close as 3.9 million miles to our star's surface, well within the orbit of Mercury and more than seven times closer than any spacecraft has come before. (Earth's average distance to the sun is 93 million miles.)

Flying into the outermost part of the sun's atmosphere, known as the corona, for the first time, Parker Solar Probe will employ a combination of in situ measurements and imaging to revolutionize our understanding of the corona and expand our knowledge of the origin and evolution of the solar wind. It will also make critical contributions to our ability to forecast changes in Earth's space environment that affect life and technology on Earth.

Extreme Exploration
At closest approach, Parker Solar Probe hurtles around the sun at approximately 430,000 mph (700,000 kph). That's fast enough to get from Philadelphia to Washington, D.C., in one second.

At closest approach to the sun, the front of Parker Solar Probe's solar shield faces temperatures approaching 2,500 F (1,377 C). The spacecraft's payload will be near room temperature.

On the final three orbits, Parker Solar Probe flies to within 3.7 million miles of the sun's surface - more than seven times closer than the current record-holder for a close solar pass, the Helios 2 spacecraft, which came within 27 million miles in 1976 and more than 10 times closer than Mercury, which is about 42 million miles from the sun.

Parker Solar Probe will perform its scientific investigations in a hazardous region of intense heat and solar radiation. The spacecraft will fly close enough to the sun to watch the solar wind speed up from subsonic to supersonic, and it will fly though the birthplace of the highest-energy solar particles.

To perform these unprecedented investigations, the spacecraft and instruments will be protected from the sun's heat by a 4.5-inch-thick (11.43 cm) carbon-composite shield, which will need to withstand temperatures outside the spacecraft that reach nearly 2,500 F (1,377 C).

The Science of the Sun
The primary science goals for the mission are to trace how energy and heat move through the solar corona and to explore what accelerates the solar wind as well as solar energetic particles. Scientists have sought these answers for more than 60 years, but the investigation requires sending a probe right through the 2,500 degrees Fahrenheit heat of the corona. Today, this is finally possible with cutting-edge thermal engineering advances that can protect the mission on its dangerous journey. Parker Solar Probe will carry four instrument suites designed to study magnetic fields, plasma and energetic particles, and image the solar wind.

Teaming for Success
Parker Solar Probe is part of NASA's Living With a Star program to explore aspects of the sun-Earth system that directly affect life and society. The Living With a Star flight program is managed by the agency's Goddard Space Flight Center in Greenbelt, Maryland, for NASA's Science Mission Directorate in Washington. The Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland, manages the mission for NASA. APL is designing and building the spacecraft and will also operate it.

Why do we study the sun and the solar wind?
  • The sun is the only star we can study up close. By studying this star we live with, we learn more about stars throughout the universe.
  • The sun is a source of light and heat for life on Earth. The more we know about it, the more we can understand how life on Earth developed.
  • The sun also affects Earth in less familiar ways. It is the source of the solar wind; a flow of ionized gases from the sun that streams past Earth at speeds of more than 500 km per second (a million miles per hour).
  • Disturbances in the solar wind shake Earth's magnetic field and pump energy into the radiation belts, part of a set of changes in near-Earth space known as space weather.
  • Space weather can change the orbits of satellites, shorten their lifetimes, or interfere with onboard electronics. The more we learn about what causes space weather -- and how to predict it -- the more we can protect the satellites we depend on.
  • The solar wind also fills up much of the solar system, dominating the space environment far past Earth. As we send spacecraft and astronauts further and further from home, we must understand this space environment just as early seafarers needed to understand the ocean.


Related:
Department members: Eugene N. Parker

NASA Sending Probe to 'Touch' the Sun -- Here's Why
June 2, 2017
Click on the image to enlarge
National Geographic, by Rachel Hartigan Shea
Today, NASA announced that for the first time in its history, a spacecraft is being formally named after a living person -- previously known as Solar Probe Plus, the Parker Solar Probe was renamed for Eugene Parker, the astrophysicist who discovered solar wind in 1958.

Related:
Department members: Eugene N. Parker

LIGO detects colliding black holes for third time
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.

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.

Related:
Department members: Daniel E. Holz
Scientific projects: Laser Interferometer Gravitational-wave Observatory

Parker Solar Probe honors Prof. Eugene Parker for his solar wind discovery
May 31, 2017
Click on the image to enlarge
UChicago News, by Steve Koppes
NASA has named the first mission to fly a spacecraft directly into the sun's atmosphere in honor of Prof. Eugene Parker, a pioneering physicist at the University of Chicago. The Parker Solar Probe will launch next summer on a mission to fly within 4 million miles of the sun's surface to study the star with unprecedented precision.

Parker, the S. Chandrasekhar Distinguished Service Professor Emeritus in Physics, is best known for developing the concept of solar wind -- the stream of electrically charged particles emitted by the sun. He was honored May 31 at a public celebration on campus that included colleagues and students from UChicago and leaders from NASA and the Johns Hopkins University Applied Physics Laboratory.

"This marks the first time a NASA spacecraft has been named for a living individual, and I am very excited to be personally involved," said Thomas Zurbuchen, associate administrator for NASA's Science Mission Directorate in Washington, D.C. Zurbuchen also presented Parker with NASA's distinguished public service medal, one of its highest honors. "Gene Parker has been an inspiration to an entire generation of scientists, including me. Having his name on humanity's first mission to a star is a fitting legacy."
Prof. Eugene Parker discusses his scientific research on the sun, including his discovery of the solar wind.
The Parker Solar Probe is scheduled to launch during a 20-day window that opens July 31, 2018. During the course of 24 orbits, the spacecraft will fly by Venus seven times to gravitationally reduce its distance from the sun. Three of the spacecraft's orbits will bring it within 3.9 million miles of the sun's surface -- approximately seven times closer than any other probe. The solar probe, which the Applied Physics Laboratory is building, will endure a solar intensity more than 500 times greater than that of an Earth-orbiting spacecraft.

"The solar probe is going to a region of space that has never been explored before. It's very exciting that we'll finally get a look," said Parker, who was on the UChicago faculty from 1955 to 1995. "One would like to have some more detailed measurements of what's going on in the solar wind. I'm sure that there will be some surprises. There always are."

The rare honor Parker is receiving, in having a space mission named after him, continues a tradition of leadership in astronomy and physics at UChicago. It includes the Hubble Space Telescope, named after UChicago alumnus Edwin Hubble; the Chandra X-ray Observatory named after Nobel laureate Subrahmanyan Chandrasekhar, a UChicago professor who worked with Parker; the Fermi Gamma-Ray Telescope, which honors Enrico Fermi, a Nobel laureate and UChicago professor; and the Compton Gamma Ray Observatory named after Nobel laureate Arthur Holly Compton, a UChicago professor.

"The naming of the solar probe is a fitting honor for Gene Parker. His pioneering work has become a cornerstone in the field of astrophysics and exemplifies the University of Chicago's commitment to rigorous inquiry and a challenging of conventional wisdom that produces new and exciting discovers across the sciences," said Edward "Rocky" Kolb, dean of the Division of the Physical Sciences at UChicago and the Arthur Holly Compton Distinguished Service Professor in the Astronomy and Astrophysics.

"Gene Parker has been an inspiration to an entire generation of scientists, including me. Having his name on humanity's first mission to a star is a fitting legacy."
- Thomas Zurbuchen, associate administrator for NASA’s Science Mission Directorate

'Nothing mysterious about it'
Parker explains that although he first predicted the solar wind in 1957, "it wasn't so much a prediction as a recognition that it was there."

Parker's early work laid the groundwork for his landmark discovery. He was a research associate beginning in 1953 at the University of Utah under Walter Elsasser, who pioneered the dynamo theory of the origin of Earth's magnetic field. In 1955, John Simpson, a veteran of the Manhattan Project, recruited Parker to UChicago to study cosmic rays.

At that time scientists knew, based on the work of Peter Biermann and Cuno Hoffmeister, that the gaseous tails of comets, which always point away from the sun, are swept away by some form of solar particle emission. Scientists thought of these solar emission particles as being shot from the sun - much like cannon balls from cannons. Parker, however, came to see the process as a flow of gas that is subject to the simple laws of hydrodynamics, becoming what he called the solar wind.

The first paper that Parker submitted to the Astrophysical Journal proposing the solar wind was panned by two eminent reviewers. Parker pointed out to Chandrasekhar, who was the journal's editor at the time, that neither reviewer had flagged any mathematical flaws in the work, and the paper was published in 1958.

"Chandra told me many years later that he was very skeptical about it, but since he couldn't find anything wrong with the math, he figured it was worth thinking about," Parker said.

The results were verified in 1962 with data collected by the Mariner II space probe to Venus, the first successful interplanetary mission. Understanding solar wind made it possible to expound the causes of magnetic storms, auroras and other solar-terrestrial phenomena.

"The solar probe is going to a region of space that has never been explored before. It's very exciting that we'll finally get a look ... I'm sure that there will be some surprises. There always are."
- Prof. Eugene Parker

After his work on the solar wind, Parker became interested in the magnetic fields of galaxies. This led to his discovery of a phenomenon now called the Parker Instability, which explains why there are places where the magnetic field bulges from the disk of a galaxy.

Parker, who is author of Cosmical Magnetic Fields - Their Origin and Activity, was elected to the National Academy of Sciences in 1967. He received the National Medal of Science, the nation's highest scientific honor, in 1989. He also received the 2003 Kyoto Prize for Lifetime Achievements for Basic Science.

Related:
Department members: Eugene N. Parker

Chicago Ideas Week: "Space Exploration: What's After The Final Frontier?"
May 23, 2017
Click on the image to enlarge
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:
Department members: Edward ''Rocky'' W. Kolb, Angela V. Olinto
Scientific projects: Extreme Universe Space Observatory at the Japanese Module, Extreme Universe Space Observatory on a Super Pressure Balloon, Pierre Auger Observatory

Prof. Angela Olinto participates in Arts Summit 2017
May 7, 2017
Washington Post, by Anne Midgette
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.


Related:
Department members: Angela V. Olinto

Michael Turner has been elected to American Philosophical Society
May 4, 2017
Michael Turner
Click on the image to enlarge
UChicago News, by Ryan Goodwin
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.

Related:
Department members: Michael S. Turner

Students, teachers craft software to make astronomy accessible to the blind
May 4, 2017
UChicago's Yerkes Observatory and partners are engaging with blind and visually impaired students to remove barriers to STEM studies.
Click on the image to enlarge
UChicago News, by Greg Borzo
Today's astronomers don't really look at stars or galaxies so much as images produced from data generated by light. If that same data were used to produce 3-D printouts, tactile displays or sound, would it open the study and pursuit of astronomy to the blind and visually impaired?

That's the kind of question the University of Chicago's Yerkes Observatory and its partners will try to answer with the help of a $2.5 million National Science Foundation grant. Over the next three years, they will develop Afterglow Access - new software that will make astronomy more accessible to the blind and visually impaired.

"Amazing pictures of stars start as numbers on a spreadsheet, and those numbers can be manipulated and presented in myriad ways," said Kate Meredith, director of education outreach at the Yerkes Observatory and the education lead of Innovators Developing Accessible Tools for Astronomy, a new research initiative from the observatory. "We won't consider ourselves successful unless within three years we have developed new computer tools with and for the blind and visually impaired that can be used in real applications, learning situations and scholarly research."

The National Federation of the Blind estimates that more than seven million Americans are visually disabled. Unequal access to quantitative information and the lack of vision-neutral tools presents them with barriers to study and master astronomy and other STEM subjects, Meredith said.

To overcome this, the Yerkes research initiative will engage blind and visually impaired students as well as sighted students and their teachers from mainstream and specialized schools for the blind. Twenty teachers and 200 eighth- through 12th-grade students are expected to participate annually. Recruiting teachers and students began this spring. While half of the participating schools will be located in southern Wisconsin and the Chicago area, the remaining schools will be selected from across the United States and its territories.

Students and teachers will participate in user-centered design and universal design processes to develop and test software and learning modules and to improve accessibility aspects of astronomy tools for educational and professional purposes. The project builds upon the success of prior National Science Foundation-supported research projects, including the development of Afterglow; Quorum, an accessible programming language; and the Skynet Junior Scholars, a program that supports collaborative astronomy investigations by young explorers using Skynet's international network of telescopes.

The research will advance knowledge about student learning related to computational thinking, the role of computation in astronomy and software design. In addition, it will help determine how participation influences student attitudes and beliefs about who can engage in computing and STEM subjects.

"Teaming up blind and visually impaired students with sighted students, teachers and professionals in the design and development of astronomy software and instructional modules will create powerful educational experiences, encourage STEM learning, and lower the barrier-to-entry for blind and visually impaired individuals interested in astronomy and related careers," Meredith said.

Investigators in the program include employees at the University of Chicago; Yerkes Observatory; Associated Universities Inc.; the Technical Education Research Center at the University of Nevada, Las Vegas; and Skynet at the University of North Carolina at Chapel Hill.

Related:
Department members: Doyal ''Al'' Harper

A Cosmic-Ray Hunter Takes to the Sky
April 28, 2017
Angela Olinto in Wanaka, New Zealand, in March.
Alpine Images for Quanta Magazine
Click on the image to enlarge
Quanta Magazine, by Natalie Wolchover
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.

Related:
Department members: Angela V. Olinto
Scientific projects: Extreme Universe Space Observatory at the Japanese Module, Extreme Universe Space Observatory on a Super Pressure Balloon, Pierre Auger Observatory, Probe of Extreme Multi-Messenger Astrophysics

U. of C. Prof Leads Stadium-Sized 'Super' Balloon Project
April 27, 2017
Click on the image to enlarge
DNAInfo Chicago, by Peter Jones
University of Chicago professor Angela Olinto is one of the leaders of a NASA project that launched a "Super Pressure" balloon this week in search of what she says is "the most energetic cosmic particles that we've ever observed."

Eighth time lucky: NASA launches super balloon to collect near space data
April 26, 2017
NASA's Super Pressure Balloon stands fully inflated and ready for lift-off from Wanaka Airport, New Zealand before it took flight at 10:50 a.m. local time April 25, 2017 (1850 EDT April 24, 2017.) Bill Rodman/Courtesy NASA
Click on the image to enlarge
Reuters, by Charlotte Greenfield
A stadium-sized pressure balloon launched by NASA in New Zealand began collecting data in near space on Wednesday, beginning a 100-day planned journey after several launch attempts were thwarted by storms and cyclones.

The balloon, designed by the National Aeronautics and Space Administration (NASA) to detect ultra-high energy cosmic particles from beyond the galaxy as they penetrate the earth's atmosphere, is expected to circle the planet two or three times.

"The origin of these particles is a great mystery that we'd like to solve. Do they come from massive black holes at the centre of galaxies? Tiny, fast-spinning stars? Or somewhere else?" Angela Olinto, a University of Chicago professor and lead investigator on the project, said in a statement.

The balloon's monitoring was only the start of a long quest which would next involve a space mission currently being designed by NASA, she added.

Related:
Department members: Angela V. Olinto
Scientific projects: Extreme Universe Space Observatory on a Super Pressure Balloon

Prof. Angela Olinto hopes telescope will help unravel mysteries of cosmic rays
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.

Photo by NASA/Bill Rodman
Click on the image to enlarge
UChicago News, by Greg Borzo
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.

Related:
Department members: Stephan S. Meyer, Angela V. Olinto
Scientific projects: Extreme Universe Space Observatory on a Super Pressure Balloon

Virtual Earth-sized telescope aims to capture first image of a black hole
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.

Illustration by NASA/CXC/M.Weiss
Click on the image to enlarge
UChicago News, by Greg Borzo
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.

Related:
Department members: John E. Carlstrom
Scientific projects: South Pole Telescope

Researchers Provide New Insight Into Dark Matter Halos
April 19, 2017
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.
Click on the image to enlarge
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.

Related:
Department members: Andrey V. Kravtsov

Prof. Angela Olinto leads project to collect data at near-space altitudes
April 6, 2017
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.
Click on the image to enlarge
UChicago News, by Greg Borzo
NASA to launch telescope on super-pressure balloon in search for cosmic rays

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.

Related:
Department members: Stephan S. Meyer, Angela V. Olinto
Scientific projects: Extreme Universe Space Observatory at the Japanese Module, Extreme Universe Space Observatory on a Super Pressure Balloon

A recharged debate over the speed of the expansion of the universe could lead to new physics
March 9, 2017
Click on the image to enlarge
AAAS, by Joshua Sokol
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.

Related:
Department members: Wendy L. Freedman

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

Related:
Department members: Angela V. Olinto

Cosmos Controversy: The Universe Is Expanding, but How Fast?
February 21, 2017
The New York Times, by Dennis Overbye
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."

Related:
Department members: Wendy L. Freedman, Michael S. Turner

Galactic X-rays could point to dark matter proof
February 2, 2017
BBC News, by Edwin Cartlidge
Prof. 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."

Related:
Department members: Dan Hooper

U of C Astronomers Discover "Twin Star," Develop Insight Into Planetary Movement
January 14, 2017
Death star HIP68468, a twin star to the sun about 300 light-years away, may have swallowed one or more of its planets, based on lithium and refractory elements recently discovered near its surface.

Illustration by Gabi Perez / Instituto de Astrofísica de Canarias
Click on the image to enlarge
The Chicago Maroon, by Stephanie Palazzolo
University of Chicago researchers have discovered a planetary system based around "solar twin" HIP68468, a star that shares many similarities with the Sun.

Unlike the Sun, this star contains abnormal amounts of lithium, levels that would be more common in a much younger star, as lithium gets consumed by a star during its lifetime.

"Lithium is like the 'smoking gun' evidence in this case that there's something unusual about this star," said Megan Bedell, a UChicago graduate student and leader of the planet search portion of this project. "[It's] kind of an unusual element in that it actually gets consumed by the star during the course of its lifetime, so as [the star] grows older, the lithium gets eaten up in the same process that fuses the hydrogen to create energy in the star."

High levels of lithium in HIP68468, which usually indicates a young star, contradicts its actual age -- 6 billion years compared to the Sun's 4.5 billion years.

"Planets have lithium, so we inferred that the extra lithium [is due to] planetary pollution on the outside of the star," Bedell said. "We also see that extra rocky material -- iron and things that make up the Earth -- tend up to be fairly prevalent in this star compared to other solar twin stars and the Sun, especially."

Therefore, Bedell's group, under the mentorship of her thesis adviser Jacob Bean, assistant professor of astronomy and astrophysics at the University of Chicago, and collaborating with a team of international scientists, including Brazilian scientist and lead author Jorge Melendez, came to the conclusion that star HIP68468 actually devoured nearby planets, which would explain the inconsistencies in the composition of the star.

Bedell's discovery of two nearby planets, a "super Earth" and a "super Neptune," also supports this hypothesis, as they seem to have migrated closer to the star over time.

"We can guess that the 'super Earth' formed somewhere close to where the Earth did [in our solar system] and the 'super Neptune' probably formed much further away," Bedell said. "In both cases today, we see them in a place where they're so close to the star and so hot that it just wouldn't have been possible for the material to condense in that place in the early solar system."

Bedell observed these planets with a Chile-based spectrograph called High Accuracy Radial Velocity Planet Searcher (HARPS). This instrument breaks down light from stars into the component colors, and researchers then use the spectrum it creates to find planets and discover the composition of stars.

"We have to keep using HARPS to observe the star many times over a period of years because you want to see the small changes that happen in the star during the time it takes for the planet to do an orbit around the star," Bedell said. "I've been going to Chile about three times a year or so for the past few years and using the same instrument to keep track of how the stars are changing through time. Using that, I can then find out whether or not they have planets and what the planets are like."

By looking at "solar twins" like HIP68468, researchers gain insight into the future of our own solar system.

"It's kind of cool to see what the planetary systems of these stars are like, especially if there's a lot of debate about how planet migration might happen over time -- maybe the system that's born around a young star doesn't stay stable like that, and it'll get rearranged over the star's lifetime," Bedell said. "So if you see a really old solar twin, maybe that's what the Sun will end up looking like."

In addition, looking at systems like the one surrounding star HIP68468 provides a "stepping stone" to questions about other Earth-like planets, Bedell said.

"[It's] got a lot of implications for the solar system and especially how common an Earth-like system is, whether other Earths out there are habitable or whether a lot of stars have this migration event that renders everything too hot to be inhabited," Bedell said. "It's nice evidence that we're on the right path for what the current theory is to explain these systems."

The group plans on continuing their research on the star system to verify their findings.

"We would like to keep taking measurements of the star's radial velocity to confirm the planet candidates that we identified and to search for additional planets," Bean said. "We also want to compare the star's unusual abundance pattern to that of other similar stars to determine how common this sort of phenomenon is."

However, even though solar twin HIP68468 might be engulfing nearby planets, Bedell dismisses fears about Earth being similarly destroyed by the Sun any time soon.

"I mean, if we're going to stick around for 5 billion years, we'll have to worry about the Sun devouring the Earth because eventually the Sun will swell up into a red giant, but I think this points to us being safe until the next phase of the Sun's life starts," Bedell said. "We're probably not going to go spiraling into the Sun at any moment."

Related:
Department members: Jacob L. Bean
Department students: Megan Bedell

Research reinforces role of supernovae in clocking the universe
January 4, 2017
Click on the image to enlarge
UChicago News, by Greg Borzo
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.

Related:
Department members: Joshua A. Frieman, Richard Kessler
Scientific projects: Sloan Digital Sky Survey

Astronomers discover dark past of planet-eating 'Death Star'
December 15, 2016
Death star HIP68468, a twin star to the sun about 300 light-years away, may have swallowed one or more of its planets, based on lithium and refractory elements recently discovered near its surface.

Illustration by Gabi Perez / Instituto de Astrofísica de Canarias
Click on the image to enlarge
UChicago News, by Greg Borzo
Solar twin could hold clues to planetary formation

An international team of scientists, including researchers from the University of Chicago, has made the rare discovery of a planetary system with a host star similar to Earth's sun. Especially intriguing is the star's unusual composition, which indicates it ingested some of its planets.

"It doesn't mean that the sun will 'eat' the Earth any time soon," said Jacob Bean, assistant professor of astronomy and astrophysics at UChicago and co-author of an Astronomy & Astrophysics article on the research. "But our discovery provides an indication that violent histories may be common for planetary systems, including our own."

Unlike the artificial planet-destroying Death Star in the movie "Star Wars," this natural version could provide clues about how planetary systems evolve over time.

Astronomers discovered the first planet orbiting a star other than the sun in 1995. Since then, more than two thousand exoplanets have been identified. Rare among them are planets that orbit a star similar to Earth's sun. Due to their extreme similarity to the sun, these so-called solar twins are ideal targets for investigating the connections between stars and their planets.

Bean and his colleagues studied star HIP68468, which is 300 light years away, as part of a multi-year project to discover planets that orbit solar twins. It's tricky to draw conclusions from a single system, cautioned Megan Bedell, a UChicago doctoral student who is co-author of the research and the lead planet finder for the collaboration. She said the team plans "to study more stars like this to see whether this is a common outcome of the planet formation process."

Related:
Department members: Jacob L. Bean
Department students: Megan Bedell

Daniel Holz: Gravitational Waves
October 13, 2016
Click on the image to enlarge
The Good Stuff
In 2015 scientists working at the Laser Interferometer Gravitational-Wave observatory, or LIGO, detected gravitational waves for the first time. But how did they do it? What is a gravitational wave? And why is confirming something that Albert Einstein predicted a hundred years ago one of the greatest scientific achievements of the past century?

Related:
Department members: Daniel E. Holz
Department students: Hsin-Yu Chen, Zoheyr Doctor
Scientific projects: Laser Interferometer Gravitational-wave Observatory

Why is this star dimming? Astronomers still don't know
October 6, 2016
This artist's conception shows a star behind a shattered comet. (NASA/JPL-Caltech)
Click on the image to enlarge
Fox News Science, by Rob Verger
A strange star in our galaxy has officially become even more enigmatic: According to data collected by NASA's Kepler space telescope, the star mysteriously dimmed over a period of a few years.

The star is called KIC 8462852, and it was already on scientists' radar for fluctuations in its brightness. So two astronomers decided to study it more carefully, using images from Kepler. They discovered that from 2009 to 2012, the star's brightness declined by just under 1 percent. Then, over a time period of six months, its brightness plunged by 2 percent. While news of their discovery first surfaced in August, their work has now been accepted for publication in an astronomy journal, the Carnegie Institution for Science announced on Monday.

"The steady brightness change in KIC 8462852 is pretty astounding," Ben Montet, an astronomer and fellow at the University of Chicago, said in a statement. "Our highly accurate measurements over four years demonstrate that the star really is getting fainter with time. It is unprecedented for this type of star to slowly fade for years, and we don't see anything else like it in the Kepler data."

Montet is coauthor on the new study about the star, forthcoming in the Astrophysical Journal.

Related:
Department members: Benjamin Montet

Physics Confronts Its Heart of Darkness
September 1, 2016
Scientific American, by Lee Billings
Cracks are showing in the dominant explanation for dark matter. Is there anything more plausible to replace it?

Physics has missed a long-scheduled appointment with its future - again. The latest, most sensitive searches for the particles thought to make up dark matter - the invisible stuff that may comprise 85 percent of the mass in the cosmos - have found nothing. Called WIMPs (weakly interacting massive particles), these subatomic shrinking violets may simply be better at hiding than physicists thought when they first predicted them more than 30 years ago. Alternatively, they may not exist, which would mean that something is woefully amiss in the underpinnings of how we try to make sense of the universe. Many scientists still hold out hope that upgraded versions of the experiments looking for WIMPs will find them but others are taking a second look at conceptions of dark matter long deemed unlikely.

Whatever dark matter is, it is not accounted for in the Standard Model of particle physics, a thoroughly-tested "theory of almost everything" forged in the 1970s that explains all known particles and all known forces other than gravity. Find the identity of dark matter and you illuminate a new path forward to a deeper understanding of the universe - at least, that is what physicists hope.

WIMPs would get their gravitational heft from being somewhere between one and a thousand times the mass of a proton. Their sole remaining connection to our familiar world would be through the weak nuclear force, which is stronger than gravity but only active across tiny distances on the scale of atomic nuclei. If they exist, WIMPs should surround us like an invisible fog, their chances of interacting with ordinary matter so remote that one could pass through light-years of elemental lead unscathed.

Undaunted, experimentalists have spent decades devising and operating enough cleverly named WIMP detectors to overflow your average can of alphabet soup. (CDEX, CDMS, CoGeNT, COUPP and CRESST are just the most notable examples that start with the letter C.) The delicate work of detecting any weak, rare and fleeting interactions of WIMPs with atoms requires isolation and solitude, confining most detectors to caverns, abandoned mines and other outlier subterranean spaces.

One of the latest null results in the search for WIMPs came from the Large Underground Xenon (LUX) experiment, a third of a ton of liquid xenon held at a frosty -100 degrees Celsius inside a giant water-filled tank buried one and a half kilometers beneath the Black Hills of South Dakota. There, shielded from most sources of contaminating noise, researchers have spent more than a year's worth of time looking for flashes of light emanating from WIMPs striking xenon nuclei. On July 21 they announced they had seen none.

The next disappointment came on August 5 from the most powerful particle accelerator ever built: CERN's Large Hadron Collider (LHC) near Geneva, Switzerland. In 2012 after it found the Higgs boson - the Standard Model’s long-predicted final particle that imbues others with mass - many theorists believed the next blockbuster result from the LHC would be a discovery of how the Higgs (or other hypothesized particles very much like it) helps produce the WIMPs thought to suffuse the cosmos. Since spring 2015 the LHC has been pursuing these ideas by smashing protons together at unprecedentedly high energies at rates of up to a billion per second, pushing into new frontiers of particle physics. Early on, two independent teams had spied a telltale anomaly in the subatomic wreckage, an excess of energy from proton collisions that hinted at new physics perhaps produced by WIMPs (or, to be fair, many additional exotic possibilities). Instead, as the LHC smashed more protons and collected more data, the anomaly fizzled out, indicating it had been a statistical fluke.

Taken together, these two null results are a double-edged sword for dark matter. On one hand, their new constraints on the plausible masses and interactions of WIMPs are priming plans for next-generation detectors that could offer better chances of success. On the other, they have ruled out some of the simplest and most cherished WIMP models, raising fresh fears that the long-postulated particles might be a multidecadal detour in the search for dark matter.

Edward "Rocky" Kolb, a cosmologist now at the University of Chicago who in the 1970s helped lay the foundations for the generations of WIMP hunts to come, declared the 2010s "the decade of the WIMP" but now admits the search has not gone as planned. "We are now more in the dark about dark matter than we were five years ago," he says. So far, Kolb says, most theorists have responded by "letting a thousand WIMPs bloom," creating ever-more baroque and exotic theories to explain how WIMPs have managed to dodge all our detectors.

There is, of course, another possibility - that WIMPs are not the solution to dark matter we should be looking for. "WIMPs emerged as a simple, elegant, compelling explanation for a complex phenomenon," Kolb says. "And for every complex phenomenon there is a simple, elegant, compelling explanation that is wrong."

Related:
Department members: Edward ''Rocky'' W. Kolb

James W. Cronin, Nobel laureate and pioneering physicist, 1931-2016
August 27, 2016
UChicago News, by Steve Koppes
Scholar remembered for groundbreaking research on particle physics and cosmic rays

James W. Cronin, a pioneering scientist who shared the Nobel Prize in physics in 1980 for his groundbreaking work on the laws governing matter and antimatter and their role in the universe, died Aug. 25 in Saint Paul, Minn. He was 84.

Cronin, SM'53, PhD'55, spent much of his career at the University of Chicago, first as a student and then a professor. A University Professor Emeritus of Physics and Astronomy & Astrophysics, he was remembered this week as a mentor, collaborator and visionary.

"He inspired us all to reach further into the unknown with deep intuition, solid scientific backing and poetic vision," said Angela Olinto, the Homer J. Livingston Distinguished Service Professor in Astronomy and Astrophysics. "He accepted his many recognitions and accolades with so much humility that he encouraged many generations to follow his vision."

Edward "Rocky" Kolb, dean of the Physical Sciences Division and the Arthur Holly Compton Distinguished Service Professor in Astronomy and Astrophysics, described Cronin as “a person of real honesty and integrity who was a mentor and friend to so many people."

"Just like in basketball, there are good players in science, but the greatest players are the ones who make the people around them better. Jim was that great player," Kolb said.

Cronin’s research that resulted in the Nobel Prize came in 1964 while he was working with Val Fitch at the Brookhaven National Laboratory. The two scientists, who were Princeton University professors at the time, observed the first example of nature's preference for matter over antimatter. Without the phenomenon, which physicists refer to as charge-parity violation, no matter would exist in the universe.

Cronin and Fitch studied the short-lived subatomic particles that appeared after the collision of accelerated protons and the nucleus of an atom. They observed indirect charge-parity violation, which is the unbalanced mixing of neutral subatomic kaon particles with their charged antiparticles. Called the Fitch-Cronin effect, the finding showed that some physical laws are violated when the direction of time is reversed. It also lent support for the big bang theory of the universe's origin.

Cronin later in his career shifted his focus, becoming co-leader of the Pierre Auger Project. The $50 million international collaboration of 250 scientists across 16 nations focused on the mysterious sources of rare but extremely powerful cosmic rays that periodically bombard Earth. The project led to the creation of the Auger Observatory, which consists of a vast array of cosmic-ray detectors in Argentina.

"It was 25 years ago since Jim and I first conceived the idea of what became the Auger Collaboration. It was definitely a great partnership as we drummed up financial and scientific support for the collaboration," said Alan Watson, emeritus professor of physics at the University of Leeds and a fellow of the Royal Society.

The collaboration has made definitive measurements on the energy spectrum of cosmic rays, on the patterns of their arrival directions, and on their mass compositions. It also has conducted particle physics research, measuring phenomena that far exceed the energies of the Large Hadron Collider.

"It's been an outstanding success, and it's still going strong," Watson said.

Drawing inspiration from Fermi
Cronin was born on Sept. 29, 1931, in Chicago, while his father was a graduate student in classical languages and literatures at the University of Chicago. The younger Cronin received a bachelor's from Southern Methodist University in 1951 before returning to the University of Chicago as a National Science Foundation Fellow to earn his master's and doctoral degrees.

Cronin met his first wife, Annette Martin, while both were students at the University. She died in 2005, and Cronin married Carol McDonald (nee Champlin) in late 2006.

Cronin began his scientific career at Brookhaven before becoming a member of the physics faculty at Princeton in 1958. In 1971, he joined the University of Chicago, where he was appointed the University Professor of Physics. He became University Professor Emeritus of Physics and Astronomy & Astrophysics in 1997.

Cronin shared a birthdate with Prof. Enrico Fermi, who earned the Nobel Prize in Physics in 1938. Cronin, who knew Fermi from his graduate school days at UChicago, organized a symposium in 2001 to mark the 100th anniversary of Fermi's birth, and was editor of the resulting book, Fermi Remembered. It included contributions from seven Nobel Prize recipients and many other scientists who studied under or worked with Fermi at UChicago.

"What's significant about Fermi is if you look through his career, he never just did the same thing. He kept moving on to new scientific challenges," Cronin once said of Fermi. The same statement also could be applied to Cronin and his research shift from high-energy physics to ultra-high-energy cosmic rays.

Cronin's honors include the University of Chicago Alumni Medal (2013), election as a foreign member of the Royal Society of London (2007), Distinguished Graduate Award of SMU's Dedman College (2004), Legion d’honneur of France (2001), National Medal of Science (1999), University of Chicago's Quantrell Award for Excellence in Undergraduate Teaching (1994), Laureate of Lincoln Academy of Illinois (1981), Ernest Lawrence Memorial Award for outstanding contributions in the field of atomic energy (1977), John Price Wetherill Medal of the Franklin Institute (1975) and the Research Corporation Award (1968).

In 1990 Cronin delivered the Ryerson Lecture, which provides an opportunity each year for a distinguished faculty member to address the UChicago community on significant aspects of his or her research.

He was a member of the National Academy of Sciences, American Academy of Arts and Sciences, American Physical Society, American Philosophical Society, Accademia Nazionale dei Lincei of Italy, Mexican Academy of Sciences and the Russian Academy of Sciences. Cronin also had received honorary doctorates from l'Universite Pierre et Marie Curie, University of Leeds, Universite de Franche Conte, Novo Gorica Polytechnique of Slovenia, University of Nebraska, the University of Santiago de Compostela, the Colorado School of Mines, and the Karlsruhe Institute of Technology. Cronin served as international chair of the College de France in 1999-2000.

Cronin is survived by his wife, Carol; daughter, Emily Grothe; son, Daniel Cronin; and six grandchildren: James, Cathryn, Caroline, Meredith, Alex and Marlo. A daughter, Cathryn Cranston, died in 2011.

Related:
Department members: James W. Cronin, Edward ''Rocky'' W. Kolb, Angela V. Olinto
Scientific projects: Pierre Auger Observatory

Angela Olinto received distinguished service professorship
July 21, 2016
Angela V. Olinto, the Homer J. Livingston Distinguished Service Professor in Astronomy & Astrophysics and the College
UChicago News
Faculty members recognized with named, distinguished service professorships

Ten faculty members have received named professorships or have been named distinguished service professors. Luc Anselin, John R. Birge, John List and Angela Olinto received distinguished service professorships; and Ethan Bueno de Mesquita, Michael Franklin, Christopher Kennedy, Jason Merchant, Haresh Sapra and Nir Uriel received named professorships.

Angela Olinto has been named the Homer J. Livingston Distinguished Service Professor in Astronomy & Astrophysics and the College.

Olinto has made important contributions to the physics of quark stars, inflationary theory, cosmic magnetic fields and particle astrophysics. Her research interests span theoretical astrophysics, particle and nuclear astrophysics, and cosmology. She has focused much of her recent work on understanding the origins of the highest-energy cosmic rays and neutrinos.

Olinto is an elected fellow of the American Association for the Advancement of Science for her distinguished contributions to the field of astrophysics, particularly exotic states of matter and extremely high-energy cosmic ray studies at the Pierre Auger Observatory in Argentina. She now leads the International collaboration of the Extreme Universe Space Observatory mission that will fly in a NASA super pressure balloon in 2017 and will be first to observe tracks of ultra-energy particles from above.

She also is a fellow of the American Physical Society and has received the Chaire d’Excellence Award of the French Agence Nationale de Recherche. Olinto has received the Llewellyn John and Harriet Manchester Quantrell Award for Excellence in Undergraduate Teaching, as well as the Faculty Award for Excellence in Graduate Teaching and Mentoring.

Olinto joined the UChicago faculty in 1996.

Related:
Department members: Angela V. Olinto

Angela Olinto: the 114th Congress Hearing - Astronomy, Astrophysics, and Astrobiology
July 12, 2016
Click on the image to enlarge
Committee on Science, Space and Technology, 114th Congress
Joint Space Subcommittee and Research and Technology Subcommittee Hearing - Astronomy, Astrophysics, and Astrobiology

Tuesday, July 12, 2016 - 10:00am

Opening Statements
- Space Subcommittee Chairman Brian Babin (R-Texas)
- Research and Technology Subcommittee Chairwoman Barbara Comstock (R-Va.)
- Chairman Lamar Smith (R-Texas)

Witnesses
  • Dr. Paul Hertz
    Director, Astrophysics Division, NASA
    [Truth in Testimony]
  • Dr. Jim Ulvestad
    Director, Division of Astronomical Sciences, NSF
    ​[Truth in Testimony]
  • Dr. Angela Olinto
    Chair, Astronomy and Astrophysics Advisory Committee (AAAC); Homer J. Livingston Professor, Department of Astronomy and Astrophysics, Enrico Fermi Institute, University of Chicago
    ​[Truth in Testimony]
  • Dr. Shelley Wright
    Member, Breakthrough Listen Advisory Committee; Assistant Professor, University of California, San Diego; Member, Center for Astrophysics and Space Sciences, University of California, San Diego
    ​[Truth in Testimony]
  • Dr. Christine Jones
    President, American Astronomical Society; Senior Astrophysicist, Smithsonian Astrophysical Observatory
    ​[Truth in Testimony]


Related:
Department members: Angela V. Olinto

Simulations foresee hordes of colliding black holes in observatory's future
June 28, 2016
New research predicts that LIGO will detect gravitational waves generated by many more merging black holes in coming years.
Courtesy of LIGO/A. Simonnet
UChicago News, by Steve Koppes
New calculations predict that the Laser Interferometer Gravitational wave Observatory (LIGO) will detect approximately 1,000 mergers of massive black holes annually once it achieves full sensitivity early next decade.

The prediction, published online June 22 in the journal Nature, is based on computer simulations of more than a billion evolving binary stars. The simulations are based on state-of-the-art modeling of the physics involved, informed by the most recent astronomical and astrophysical observations.

"The main thing we find is that what LIGO detected makes sense," said Daniel Holz, associate professor in physics and astronomy at the University of Chicago and a co-author of the Nature paper. The simulations predict the formation of black-hole binary stars in a range of masses that includes the two already observed. As more LIGO data become available, Holz and his colleagues will be able to test their results more rigorously.

The paper's lead author, Krzysztof Belczynski of Warsaw University in Poland, said he hopes the results will surprise him, that they will expose flaws in the work. Their calculations show, for example, that once LIGO reaches full sensitivity, it will detect only one pair of colliding neutron stars for every 1,000 detections of the far more massive black-hole collisions.

"Actually, I would love to be proven wrong on this issue. Then we will learn a lot," Belczynski said.

Forming big black holes
The new Nature paper, which includes co-authors Tomasz Bulik of Warsaw University and Richard O'Shaughnessy of the Rochester Institute of Technology, describes the most likely black-hole formation scenario that generated the first LIGO gravitational-wave detection in September 2015. That detection confirmed a major prediction of Albert Einstein's 1915 general theory of relativity.

The paper is the most recent in a series of publications, topping a decade of analyses where Holz, Belczynski and their associates theorize that the universe has produced many black-hole binaries in the mass range that are close enough to Earth for LIGO to detect.

"Here we simulate binary stars, how they evolve, turn into black holes and eventually get close enough to crash into each other and make gravitational waves that we would observe," Holz said.

The simulations show that the formation and evolution of a typical system of binary stars results in a merger of similar masses, and after similarly elapsed times, to the event that LIGO detected last September. These black hole mergers have masses ranging from 20 to 80 times more than the sun.

LIGO will begin recording more gravitational-wave-generating events as the system becomes more sensitive and operates for longer periods of time. LIGO will go through successive upgrades over the coming years, and is expected to reach its design sensitivity by 2020. By then, the Nature study predicts that LIGO might be detecting more than 100 black hole collisions annually.

LIGO has detected big black holes and big collisions, with a combined mass greater than 30 times that of the sun. These can only be formed out of big stars.

"To make those you need to have low metallicity stars, which just means that these stars have to be relatively pristine," Holz said. The Big Bang produced mainly hydrogen and helium, which eventually collapsed into stars.

Forging metals
As these stars burned they forged heavier elements, which astronomers call "metals." Those stars with fewer metals lose less mass as they burn, resulting in the formation of more massive black holes when they die. That most likely happened approximately two billion years after the Big Bang, before the young universe had time to form significant quantities of heavy metals. Most of those black holes would have merged relatively quickly after their formation.

LIGO would be unable to detect the ones that merged early and quickly. But if the binaries were formed in large enough numbers, a small fraction would survive for longer periods and would end up merging 11 billion years after the Big Bang (2.8 billion years ago), recently enough for LIGO to detect.

"That's in fact what we think happened," Holz said. Statistically speaking, "it's the most likely scenario." He added, however, that the universe continues to produce binary stars in local, still pristine pockets of low metallicity that resemble conditions of the early universe.

"In those pockets you can make these big stars, make the binaries, and then they'll merge right away and we would detect those as well."

Belczynski, Holz and collaborators have based their simulations on what they regard as the best models available. They assume "isolated formation," which involves two stars forming in a binary, evolving in tandem into black holes, and eventually merging with a burst of gravitational wave emission. A competing model is "dynamical formation," which focuses on regions of the galaxy that contain a high density of independently evolving stars. Eventually, many of them will find each other and form binaries.

"There are dynamical processes by which those black holes get closer and closer and eventually merge," Holz said. Identifying which black holes merged under which scenario is difficult. One potential method would entail examining the black holes' relative spins. Binary stars that evolved dynamically are expected to have randomly aligned spins; detecting a preference for aligned spins would be clear evidence in favor of the isolated evolutionary model.

LIGO is not yet able to precisely measure black hole spin alignment, "but we're starting to get there," Holz said. "This study represents the first steps in the birth of the entirely new field of gravitational wave astronomy. We have been waiting for a century, and the future has finally arrived."

Citation: "The first gravitational-wave source from the isolated evolution of two stars in the 40-100 solar mass range," by Krzysztof Belczynski, Daniel E. Holz, Tomasz Bulik, and Richard O’Shaughnessy," Nature, Vol. 534, pp. 512-515, June 23, 2016, doi:10.1038/nature18322.

Related:
Department members: Daniel E. Holz
Scientific projects: Laser Interferometer Gravitational-wave Observatory